Hi everyone,
First post here but a longish time lurker. I’m not a pro, just a future diy homebuilder in central Texas (40 NW of Austin). I’m trying to design a roof system for my house with a screwed down metal roof on purlins and R50 insulation (dense pack cellulose) over a cathedral ceiling. I’m trying to build economically as possible. I will have rainwater collection for my water supply.
I have two major roof concerns:
1.) future leaks as the screw rubber washers eventually deteriorate
2.) venting of the hot air from the roofing metal.
I have a proposed design as shown in the attached drawing. I show a vent channel but would I be better off just adding more insulation instead?
I suppose a radiant barrier would also be highly advisable too which I didn’t show in the drawing. Should in this design, the radiant barrier be placed directly under the metal panels?
Would a layer of roofing felt under the metal to provide a drainage plane for my leak concerns be a bad idea?
Sorry for all the questions. I look forward to hearing from the professionals.
Regards,
Teri Lum
Replies
HI Ms Chips,
This reply will help to get your post noticed. I am by no means the "professional" you are looking for on this board, but I am considering spray foam insulation for the underside of my roof, and the contractor I'll probably go with said, with spray foam there is no need to vent the roof. Maybe an option for you.
Good luck and welcome to the asylum!
Kevin
I agree with Mr. Biil - the concealed fastener systems with snap-lock seams are the way to go. And IMO they look better than the old-fashioned corrugated panels. I'm a DIY too, and last Fall I put up a shed roof using the SL-16 panels from http://www.betterbuiltmetal.com/abc/pdfs/ABC_SL16.pdf . They have dealers all over the country and the material ships from several big warehouses. Here is a picture of the building I roofed. The panels go on quickly, but the trim work takes a lot of time.
Hi TJK,I see you're an amateur astronomer too! I'm building an observatory for a friend in the 4 corners area of Colorado. See http://tinyurl.com/24h7hfBoats234 seems to have a low opinion of hidden fastener type of roofing. I have to digest what he and CapnMac said to make an intelligent opinion.-- Teri
Yeah, the main roof is on rollers and moves 11 feet to the north when its open. The reason I chose metal for the roof is because asphalt shingles are 3X heavier. Thanks for that link to the construction pics - your friend's observatory has an interesting design for the pier column.On the main topic, I'm not sure why exposed fastener systems would be any better. Seems to me that the fewer joints and holes exposed to moisture, the better.
Teri,
Take a look at Fabral's ssr roofing system. No exposed fasteners to leak. I am preparing to use this on my detached garage this spring to replace the 25 year old three tab shingles. It appears to be very easy to install and almost foolproof as far as leaking.
http://www.fabral.com/res-1-1-2ssr.asp
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
with R50 cellulose I see no need for a vent channel or any venting at all.
For concerns with elaks and a secondary barrier and radiat heatgain do this instead - Sheathe it with plywood. Dry in with 30# tarpaper or better yet The new synthetics like RooftopgaurdII or Titanium UDL.
Then run furring ( purlins) horizontally to sticker your metal roof on.
For a radiant barrier, add a foil over the tarpaper. radiant heat reflectors need an inch of free air space immediately in front of them to work
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stay away from purlins and use 5/8 plywood. with a good wind your roof be gone with purlins.two ways to screw up concrete 1) concrete driver 2) concrete finisher
please explain
is the venting issue dependent on the R value?
In part, yes. Still neeeds a good barrier on the living side, but basically, good insulation eliminates the existence of a dew point where condensation can form. Also, in his climate, heat from above will more likely be driving moisture towards the interior rather than letting it move out to the metal.venting could help some with taking off some of that heat gain, but is not needed for vapor control in his case
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Hi Piffin, Why did you suggest furring/purlins under the metal if there is a deck? Is there a problem with roofing felt directly against the underside of the metal? Or is this to reduce some of the heat gain?-- Teri (57 year old woman)
for his desire to have venting
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Yes, I want venting but wouldn't horizontal sleepers be rather poor for venting unless the ends are open somehow.If they are open, dust can get in very easily. Central Texas can very dry and sometimes New Mexico and west Texas comes to visit us :-)-- Teri
I'd do like Brownbagg says and do the plywood, followed by the synthetic paper. I did a metal roof, (aluminum shingles) that have exposed nails. The manufacturers 30 or 50 year leak free guarantee required that method. So far, no leaks.
As far as the insulation, there are so many ways that you could go. If codes in your area allow it to be unvented, I'd do that. Foam, sprayed in, or a combo of dense pack cellulose with foam sheets.
i live in a home built in 1873 with a metal roof
being a gc i have installed numerous metal roofs all screwed down over the last 30 years
i have noticed one thing even here north of the 49th dont use a dark colour of steel as it absorbs heat and will literally burn off the finish in not to long a time
mine gets repainted about every 25 years (due now)
start applying your steel sheets starting from the one farthest away from the prevaling winds using only sheets that have the double lap profile for the joint
at the peak use a fitted peak to reduce the chances of a leak
when applying sheets put a screw at the top then one in the middle and lastly one at the bottom before doing the balance otherwise you will get panel creep which will allow the joint to leak and also throw your sheets out of whack over a distance
i have seen a lot of leaky roofs and they always seem to be because the installers were nothing but a bunch of labourers because people feel any dumbass can install a steel roof
Hi Dude,I'll be using a white roof. I'm building in Texas where cooling is the problem. A dark roof is just so dumb here. Thanks for the suggestions on first screw placements.-- Teri
For longevity's sake, I'd try to find the money in the budget for a hidden fastener roof system. That takes care of one of your concerns (and a valid one, IMHO). I'd also spring for a Kynar finish over polyester.
As mentioned above, I'd stay away from a purlin system unless you want to potentially collect your roof from your neighbor's yard after a major wind event.
My major concern with metal roofs (my primary line of work for 20+ years) is the flashing details. If not done properly, that's where your leaks will manifest themselves. I get lots of calls for repairs to leaky waste vents, sky lights, and valleys on metal roofs installed by others.
I agree with the others about the synthetic underlayments.
I'm not an insulation expert and the rule's are changing, but still vary somewhat from climate to climate. In my climate (KY), I'd go with closed cell foam or dense pack cells.
http://grantlogan.net/
It was a while ago, but I was in the biz of putting preformed metal roofing and siding on commercial and industrial buildings, and the jobs were all over your part of TX, then over across LA, over the rest of TX, and up into OK.
We put down thousands of squares of preformed metal roofing on churches, stadiums, industrial plants, housing units, and many commercial buildings.
Always fastened through the high rib, neoprene-washered fasteners went directly to purlins, with no intermediate decking.
Properly engineered and installed, a system like this will be trouble free for many years. Literally hundreds of thousands of squares of ag panel (industry term for the light gage preformed roofing for barns) is screwed directly onto purlins all over TX, and keeping things dry below.
Our installations kept folks and their gear dry in places like Plaquemines, LA, and I'll bet you know how wet it can be over there.
"Always fastened through the high rib, "It salways a good idea to read the instructions of the manufacturer. Most call for fasteneing in the field not the rib, and with good reason. Unless it is the heavier structiural metal, the pan wil deform when you get the screw tight enough in the rib to seat the washer. Then it will not resist wind as well, and the vibrations will be hard on the fasteners.Best to do it right instead of what seems right
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I would definitely second everything seeyou said. Especially the parts about the kynar finish and the flashing details. If you want foolproof longevity, standing seam is your metal.
Oh, and dont do the purlins.
Naive but refreshing !
Hi Everyone,
Thank you to all (I suppose I should say Y'all) for your comments.
There seems to be a number of people (Brownbagg, Sandalboy, Seeyou & Woody1777) completely against the purlin idea. I will also be building a pole barn for a shop and storage from a "kit" which has brackets to attach the purlins to the trusses, they look like "hurricane clips" from their video. They (Sutherlands) "guarantee" the design for 120 mph winds. For those saying I'll have to collect my roof from the neighbors, where is the likely separation? At the metal to purlins? Purlins to trusses? I would use hurricane clips to attach the purlins. Gene Davis seems positive about the metal panels attached to purlins based on his previous biz.
I'd like to use the hidden fastener type metal roof but the cost is a lot more than the budget. That type of roofing certainly eliminates leaks from screws. I'm still leaning to the screw down metal panels but want some sort of extra protection from possible water entry at the screws especially if I have all that cellulose under it which could absorb a lot of water before my interior ceiling collapsed from the weight of waterlogged cellulose. I may be worrying about an insignificant water problem but I want to be sure. Seeyou and Woody1777 says that the flashing detail is the most likely (major) water entry problem. Good point, to paraphrase: "it's the details stupid" :-)
Gene seems positive about the metal panels attached to purlins. He also said: "Always fastened through the high rib ... " I know this is the proper method for the corregated metal but Fabral shows screws on the flat sections of the panels too. I was thinking of using their panels with only the high ridges on the edges and shallow ridges between (probably for some stiffening).
For those advocating a deck under the metal panels, would OSB instead of plywood be okay? Or is OSB a dirty word here? I know it's not okay in Dade county FL. I'm trying to keep within the budget.
If I have to abandon the purlins, Piffin's suggestion about foil and 30# felt or a newer material over the decking and furring strips seems like the best alternative. However, won't the radiant barrier be eventually rendered ineffective from dust/dirt, especially if the shiny surface is facing up?
In the image in my original post, I show a vent space above the cellulose. What I had in mind was a Tyvek layer against some wire backing (to keep it from ballooning into the vent space) to constrain the cellulose. Anyone have a better idea or comments? From another forum, one person was adamant about including the vent space to minimize heat gain. I want to minimize or eliminate mechanical air conditioning.
I'm including another drawing without purlins showing a decking with sleepers. This still has venting above the cellulose insulation.
Oh (yet) another question, since I will need rather deep section I-joists for insulation, would 24" (or more) centers be adequate support for the decking?
Thanks again for the comments.
-- Teri
how is dust going to get to it?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Those washers have a pretty decent lifespan. I grew up on a farm with three old barns covered with these roofs.But if you've got a leak, clambering on the roof is not good times. I can speak from experience. Denting the roof or falling are real possibilities. In the sun, the metal will be extremely hot on an exposed hand.I wouldn't want it on my house. The newer barn, ~20 years old, has a number of leaks from failed washers. They just land on a concrete slab, so who cares?I don't think it looks bad, and yeah, it gets you a white roof and - I dunno - 20 years (?) of service. It might be just the thing for you.
fabral is to be screwed in the flat. The washers have appx. 20 yr lifespan. I have spent a lot of time puting silocone over washers after 20 yrs. never had callback.
Yes, the washers have a decent lifetime but in 20 years (if they last even that long) I'll be 77 years old and I really don't want to be climbing around on roof tops! :-) I plan on at least 26 ga metal roofing. I helped a friend put some of that tinfoil corregated metal Home Depot sells (29 ga I think) and you can't walk on it without crushing. We had to use 2x6's to distribute our weight..-- Teri
Ms Chips,I've been doing these roofs since '77. Do a few hundred square every year and don't have any leaks. The new dac or over cup washers should outlive you. Usually screw down to 2x4 purlins and have never had any blow off despite living in hurricane alley. Screw down has a higher wind rating than concealed fasteners.If you use cels you don't need a radiant barrier.If you use decking don't use osb, doesn't seem to hold screws well.Just my experiences.KK
Hi KK,One roofing/metal supplier (Metalmart) showed me those over cup washers screws. They look a bit more visually obvious but function is more important to me (I'm an engineer) . As I understand these over cup washer screws prevent over tightening of the screws and I suspect keep damaging UV from the rubber washer. Are there any with a silicone washer for ultimate (hopefully not ultimate price) life?Interesting that you say screw down roofs are better for high winds. Makes sense since there are more fastening points than concealed fastener systems. The Fabral panels I'm considering are supposed to be fastened in the fields which would be every 9" between the major ridges.You're another vote for no vent space. I'm still leaning toward the vent space with the radiant barrier under the decking. In my climate, I want minimal heat from the ceiling but the R50 cels may make that a moot point.Your recommendation for plywood over osb is noted. Any further observations on screw retention you care to share? Were there pullouts or ripping of the osb observed? I'm not questioning your experience, just curious and I want to understand.-- Teri
The problem with purlins is the air space available for positive pressure under the roof when negative pressure is created above the metal during high winds. With solid sheathing, the pressure is against the sheathing rather than the roof metal.
Gene Davis seems positive about the metal panels attached to purlins based on his previous biz.
I wonder why he's not still in it? Commercial details are a little different from residential and I've been in very few metal roofed commercial buildings that don't leak a little. For a lot of commercial buildings, a little leak is not catastrophic. It usually is for a residence.
"Always fastened through the high rib ... "
The roof needs to be installed to the manufacturer's specs.
would OSB instead of plywood be okay?
Plywood would be best with osb a close second.
In the image in my original post, I show a vent space above the cellulose.
Look into dense pack cellulose.
but want some sort of extra protection from possible water entry at the screws
Sorry, but there's no magic bullet for that. Good luck.
View Imagehttp://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
You said: "The problem with purlins is the air space available for positive pressure under the roof when negative pressure is created above the metal during high winds. With solid sheathing, the pressure is against the sheathing rather than the roof metal."That would seem to preclude sleepers as Piffin suggested.I intend to use dense pack cellulose.A deck with roofing felt or one of the newer materials should be a secondary barrier to minor leaks.-- Ter
That would seem to preclude sleepers as Piffin suggested.
Yup.
I intend to use dense pack cellulose
Then there's nothing to vent.
A deck with roofing felt or one of the newer materials should be a secondary barrier to minor leaks.
There's a coresponding hole in the underlayment for every hole in the metal. I never think of the underlayment as anything except a temporary covering to protect the building until I finish the roof. If you're already relying on the underlayment to keep the building and it's contents dry before you start building, there's gonna be some dissapointment.
The underlayment will divert condensation to some degree if it occurs.http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Just to add my 2 cents.
Granted, I'm biased due to the fact that I've used a roof system almost identical to your drawing. Successfully I believe.
Purlins are great IMO. I use 2x4 PT purlins on 2' centers. Any screw head leaks are minimized and no rotting will occur.
SnapLok, standing seam and other hidden fastener systems are top of the line for leak prevention (and more costly as you've seen). But are the 1st ones to end up in the neighbors yard in my hurricane area. Granted, barns and stogage sheds with 1x4 purlins/29ga ag panel and no inner structure go 1st but thats comparing apples to oranges.
The main reason is the eave treatment, or lack of it. Your SnapLok or standing seam is usually in 12" or 16" panels, consequently your screws are that far apart also. That 12-16" space is a good place for high winds to get its fingers under and start pulling.
You can apply screws on the eave of a standing seam system (called storm stitching in my area) but it defeats the purpose of a hidden fastner.
SeeYou has also posted an eave detail where the top panel is crimped into the drip edge. I think this detail is more for copper roofs than metal, as all hidden fastener panels in my area are 24Ga. Too thick to bend in the field with hand tools.
Blowing 2-3" of CC foam to the back of the panels will alleviate all uplift and leak problems ($1.75/sq.ft in my area) and no additonal insulation will be required for your area.
I put a radiant barrier on the back side of my purlins, then I'm shooting foam on top.
Good Luck
Ray
Just a final note on purlins. Standard prctice in my area was 60" on center for metal purlins - Commercial bldg. Now it's 48" with the adoption of the IBC. Saw a 140mph design bldg. last week. Purlins 3' OC with 24 ga. 'R' Panel.
Hi Ray,You gave me a lot to think about. Let me digest it and I'll probably have some more questions on how your roof design differs from the one I showed in my sketch.-- Teri
Hi Ray,You said you used a roof design similar to mine. Other than using foam insulation how is it different? Also, I didn't quite follow how you applied the foam. Sounds to me like you shot the foam on top of the radiant barrier to the depth of the purlins and then put the metal on.You said some in your area use screws on the eaves for "storm stitching" for hidden fastener roofs, other than the appearance, wouldn't any leaks at the eaves be of minimal consequence?My house design is to have a large overhang/porch all around the house for maximal shading in hot weather. Also, it will keep almost all rain off the siding except for some wetting in a gusty thunderstorm which should be a good thing too. The hip roof line (Dutch hip north side only) is from the edge of the overhang/porch to the peak. The insulated portion of the roof will start from an extension of the vertical walls. I expect venting would be from the eave area soffit vents at the lower section and ridge vents at the top.The house will only have partition walls for privacy and no ceiling (might get noisy with company but I live alone) for maximal ventilation. There is no attic. Heating will be from floor registers using an insulated crawl space. Cooling will be mostly by ceiling fans and good ventilation at night and closing up the windows by day, that's the reason for the R50 roof. I may have a few window AC's for the few days when it it gets unbearable.Thanks,
Teri
The house will only have partition walls for privacy and no ceiling (might get noisy with company but I live alone) for maximal ventilation.when I lived in corpis chriti. that how they had all the homes, no insulation, those roll out slat windows and this uge ceiling fan in the attic that ran off leather belts. one motor and about six fans. the walls was eight feet tall with no ceiling, you was looking at the bottom of the roof, no insulation at all. all the exterior walls had french door going out on the covered porch. Each room had the doors. open all the doors and it was like a carport.porches was like 10 feet deep with the roof being seven feet off the ground. hugh overhangs.two ways to screw up concrete 1) concrete driver 2) concrete finisher
Hi Brownbagg,I think I'll use regular ceiling fans :=) Getting on a tall ladder to change out the leather drive belt is not something I think I would be comfortable with.-- Teri
Teri,
You said you used a roof design similar to mine. Other than using foam insulation how is it different? Also, I didn't quite follow how you applied the foam. Sounds to me like you shot the foam on top of the radiant barrier to the depth of the purlins and then put the metal on.
The roof I'm speaking of is a 12/12 pitch using 2x8 rafters. I have 2x4 purlins on 2' centers. Beneath the purlins( between the rafters) I have a radiant barrier-bubblewrap foil.
I initially planned on putting FG batts beneath the foil but nixed that after doing more research.
I then put foil backed polyiso sheets between the rafters (maintaing a 1" air gap from the 1st radiant barrier. So, I essentially have 2 radiant barriers.
I will shoot 2-3" of foam to the the back of the foam sheets. Followed by 5/16" ply and then T&G cedar. My open space is aprx. 25'x30'
This is a 2nd home/camp and I have the luxury of no schedule.
I sprayed 3" of CC foam on the bottom of the roof deck on the house I'm finishing up now. I am so impressed with the insulation quality that I changed the plan for my camp.
A candle keeps the place warm and if I leave the fridge door open too long I get cold. OK, slight exaggeration.
My insulation guy wants me to take a trip to N. La where he insulated a horse barn. The foam is sprayed directly to the metal panels. The bldg. is conditioned, but stays open most of the day. Very comfortable day and night according to him.
CC foam is just being recognized by Florida code as a method to prevent uplift by tying the sheathing to the rafters, either by foaming the whole thing or just using foam fillets.
I've have little experience with cellulose, but from what I've seen and read in the past, I would think that you would get very little value from adding the radient barrier on top of 16" of cells. Cellulose is far superior to FG batts, but I understand that they both retain heat.
Since your still in the design stage, get in contact with an isulation contractor, and visit a few projects.
Great design plan with the large overhangs IMO. If you can keep the sun off, 1/2 the battle is won in a cooling climate.
Good luck
Ray
Hi Ray,Ok, I think I understand your roof design now. How are you going to vent the space between the metal and the rafters? End vents?You are of the foam insulation camp I see. Foam has higher R value per inch but price-wise, cellulose is ahead if you have the space.Interesting that Florida is considering the foam as a glue reinforcement for the roofing. Not a surprise having read of people pleading for advice on how to remove it from their hands. My experience was with gloves so no (significant amount) foam on my skin.Yeah, with R50 of cellulose planned I know there are diminishing returns with a radiant barrier. I have to decide how many sigma I want to be out on the curve :-) I'm still pondering the value of the radiant barrier. From most of the responders, venting for moisture with the R50 is not needed in my cooling climate.Thanks for the compliment on the large overhangs. Actually, I'm planning on designing like early settlers did here before AC. Tract homebuilders here (and probably elsewhere) build houses
just all wrong for the climate. I'm designing and building MY house, not an investment.-- Teri
Opps, I forgot the latest sketch in my last reply. -- Teri
I know this is the proper method for the corregated metal but Fabral shows screws on the flat sections of the panels too.
If I'm remembering the destruction manual from Fabral right, the "flats" are for wind uplift, which is especially needed with open purlins (but may not be with a solid deck). Either really works--you may find more residential roofers more comfortable with deck instead of purlins, but far enough out in the country, the farm-n-ranch roofers will have built plenty of purlin roofs for barns and the like.
Now, my question is not on your proposed section, but on the ends of that section. What detail are you going to use to get the venting air in, and then out again? See, that leads to the next question, which is how are you venting across valleys and/or hips?
In our climate (I'm only about 100 miles east of you), getting the insulation plane up against the roof makes very real sense. I've had some success with combining the wall insulation plane into the roof-oriented plane, too (conditioned attic is very nice, especially for the mechanicals). I'm not entirely sure venting the roof is really that needful (the arguments made over at buildingscience are very compelling). It's a tad drier in humidity and annual rainfall than here, but not the arid driness out to the other side of the Pecos, either. Introducing humid air into the roofing just has a few more "I wonders" than I'm comfortable with--especially given that you are in a climate with more extremes than mine here in the Brazos river valley.Occupational hazard of my occupation not being around (sorry Bubba)
Hi CapnMac,You gave me a lot to digest. Thanks for your comments.I'll comment later.-- Teri
Hi CapnMac,You said: "What detail are you going to use to get the venting air in, and then out again?"Well, that's why I show a vent gap under the purlins in my first sketch and also under the deck in my second and latest sketch (attached in previous post). Not all the details are worked out yet, but soffit type vents and ridge vent would be the logical way. That's why I asked for comment in the first place since purlins are normally horizontal and any air flow would have to be horizontal from presumeably edge vents of some sort, that's why I asked Piffin why sleepers in his suggested design.Venting is solely for keeping out as much heat as possible.-- Teri
I have 2 cents to offer on this topic also.I just built a house with a steel roof. I screwed the steel in the flats over 5/8 sheathing and roofwrap. (per mfg specs)The consensus around here (Southern IL) is the solid decking keeps the steel from moving around as much, and causing the washers to wear less over time, therefore reducing the chance of leaks and lenghtening the service life of the washers.A medium to large guy named Alan, not an ambiguous female....
NOT that there is anything wrong with that.
Hi Alan,I am leaning toward the solid decking for a number of reasons, cost is probably not much more than all the purlins (and makes a safer platform to work from) and it enables putting a water barrier/drainage plane under the metal in case of minor leaks from any screw hole leaks. Seeyou's opinion on this is negative. I'm trying to understand his reasoning. I know theory and reality often don't match but adding roofing felt or similar can't hurt.-- Teri
Seeyou's opinion on this is negative. I'm trying to understand his reasoning. I know theory and reality often don't match but adding roofing felt or similar can't hurt.
No - my opinion of using underlayment (Titanium is great stuff) is not negative. Relying on it as a secondary roof in the design stage is what I'm poopoo-ing. http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Hi Seeyou,Ok, so do you have any suggestion beyond putting on a stand seam or flat seam copper roof?Granted (no pun intended), the screws will cause holes through the underlayment. The holes should remain close to the original screw penetration size. It is the metal's expansion and contraction that both elongates the screw's hole and wears out the rubber washer from scrubbing against the metal. The screw should remain fairly stationary (relative to the decking).Water can enter from the worn rubber washer through the hole in the metal. Where can it go? If the screw hole through the underlayment is plugged by the screw then the water would have to travel between the metal and the underlayment. Eventually it would have to evaporate or drain down toward the roof edge.Okay, if the screw hole through the underlayment is not tight against the screw, then water can enter through that path to the deck surface under the underlayment. Water can now get between the underlayment and the decking. The water can damage the decking if it doesn't diffuse out somehow, perhaps by evaporation.Now we have only the screw in the decking left. Will it be loose in it's hole? If so, then water can enter through that penetration to wet the insulation and ceiling below. If not, then the decking is the final barrier.Now, backing up to the screw penetration through the underlayment. What if there was a way to seal that penetration? Maybe some of the gooey mastic/rubber used to seal the seams on metal roof? How long does that stuff last? Anyone have any anecdotal observations on the longevity of that sealant? Or any better sealant? Bithuthane?I'm not trying to pick a fight but I don't believe in the American management style of rolling over dead (or crying to their legislators) when confronted by a problem (like American auto makers)? Why are the Japanese & Taiwanese whipping our butts? They don't accept defeat. Some will argue cheaper labor or lax safety rules but the facts don't support that. The behave more like America did in the "old days".I'm trying to understand the problem so I or someone else can come up with a solution. When I worked for a former employer, Phd experts formerly with IBM, FLATLY DECLARED an idea a co-worker and I came up with couldn't work. Well, I just went to work to figure out solutions to the stated problems. With some other people that didn't just say no way, we came up with a method that did work and was a very manufacturable method. I can conservatively say, the company saved millions of dollars from an experiment that cost less than $10K and yielded a higher performance product.I'll get off my soapbox now.-- Teri
Granted (no pun intended), the screws will cause holes through the underlayment.................
I'm not argueing with anything you've said. What I'm taking issue with is the mind set going into this that the underlayment will take care of the design flaws in the roofing material. That type of thinking can cause heartache down the road.
I think you're going in the right direction by eliminating the purlins and using plywood. And you certainly need an underlayment.
But, by the time you spend extra money on high tech underlayments and special and extra screws and washers, you may be getting close to the price of snap lock roofing. I'd check into that if I were you.
The idea that a hidden fastener roof is more likely to be blown off is preposterous if they both are installed correctly. More screws or clips can be added over the recommended amount if one is nervous.
I've installed a couple of these roofs:
http://www.metalsales.us.com/VerticalSeam/
IIRC, the material cost was a little over $200/sq for 24 ga. with a Kynar finish - 16" OC. I think it's also available in 26 ga and 29 ga. 29 ga is a little thin.
The suppliers near you should have something similar.
So to recap - consider using felt (less material cost - more install labor). Revisit hidden fastener systems vs. trying to hotrod exposed fastener systems.
Also, look into plain galvalume with out paint if that type of look is acceptable.
Good luck. And please keep us posted as this progresses.
http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Edited 2/8/2008 7:18 am ET by seeyou
Hi Seeyou,Sorry if my last post sounded like a rant against you. I see problems as a challenge to solve.Your points are very valid and I do intend to reinvestigate costs for hidden fastener roofing. Labor vs. material costs have to be weighed. I intend to do a lot of the construction myself but the roof will be contracted out. I don't suffer from acrophobia but I DO have FALLophobia :-)I was also surprised to hear that concealed faster roofing being blown off in high winds. Someone said it was the wind getting under the (eave?) edge and peeling it off. That indicates that a better edge fastening treatment is required. Are there standard edge clips? Or would I have to make my own?It seems that every metal roofing maker now makes a snap lock "standing seam look" roof panel these days. Plain galvalume would be fine with me and is rather common here but one supplier said they only warrant it for 10 years vs. 20 years for kynar-paint panels. As I intend to use rainwater collection for my water supply, I want something that will last as long as possible before I have to try to paint it with something safe.Thanks for your input and I'll keep everyone posted.-- Teri
I was also surprised to hear that concealed faster roofing being blown off in high winds. Someone said it was the wind getting under the (eave?) edge and peeling it off. That indicates that a better edge fastening treatment is required. Are there standard edge clips? Or would I have to make my own?
Sounds like installer error to me. On the systems that I'm familiar with, the hidden fastener pans wrap around or lock into a drip edge that's secured to the deck. Seems like the exposed fastener eave would catch more wind.
In my career, I've had to deal with three hidden fastener blow offs. One was done by others, but I replaced it. It had not been fastened properly - we could tell from the nail pattern on the roof deck.
The second was one that I did. The whole roof structure came off, but the metal mostly stayed on the structure.
The third was one of mine also. My installer was skipping clips and I caught him at it and ran him off. Before, I could do anything about it a windstorm hit and 10 squares of copper came off the roof.
I have seen lots of exposed fastener roof blown off, however. But most of them were thinner gauge.http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Grant,
A while back you posted an eave detail that locked to the drip edge- you still got that drawing handy?
Is there another locking detail that can be used for the typical 24ga pans... snapLok etc.
I think standing seam makes a great roof (and more costly) and wouldn't hesitate to use it for Teri's project if it was in the budget--- she is not in a high wind area.
We have quite a few grocery stores and strip malls that lose a portion of their standing seam panels after a windstorm, Considerably more than the commercial bldgs. in the area with R panel exposed fasteners.
I've never dug deep and investigated the root cause, but taking a quick look and it appears the blow off is due to the attachment points being 16" apart at the eave.
I still disagree with ya on properly attached purlins vs. solid decking<g>
Ray
A while back you posted an eave detail that locked to the drip edge- you still got that drawing handy?
Yeah, I'll have to dig for it. I think I posted it in a thread started by Mike Hennesey about an outdoor BBQ. I've used it on 24 ga steel, but it's tough.
The 24 ga steel roofs around here usually have an inch or so hem bent back up the slope of the roof to receive the bottom of the pan. It's a little counter intuitive to getting the water off the roof, but it holds the roof on. I'll see if I can find a detail for it also.
Hey what happened with Brady (LSU round ball coach)? Just heard he got fired.http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Hey what happened with Brady (LSU round ball coach)? Just heard he got fired.
The press conference looked like a funeral announcement. Brady was at the podium sobbing... his wife, sitting behind him was bawling her eyes out.
Brady got LSU to the final four 3 years ago....but attendance at the games has sucked ever since Shack left.
Need some new blood to stir up the crowd.
I miss Dale Brown.http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Yep... he da man.
Sports talk has been talking on how Brown left with a shadow over the school-NCAA investigation.
Forgot all about it till they brought it up.
He was at the big dance a couple years ago doing some color commentary. I think he may be in politics now.
I'm still a Marvelous Marv Harshman fan.
Well, since we've hijacked this thread.............
Dale always took time after the game to walk out on the floor, win or loose and congratulate the player from the other team that had done him the most harm that game.
I wrote him a letter mentioning this when he retired and he wrote me back saying how a coach he had played against when he was young did that to him and he thought it was the best compliment he'd ever gotten in his life until a Kentucky fan sent him a letter congratulating him on his great career. He cracks me up.
You guys are giving TN a hard time.
http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Edited 2/9/2008 3:33 pm ET by seeyou
Edited 2/9/2008 3:34 pm ET by seeyou
You guys are giving TN a hard time.
We were until we did the stone cold choke in the last minute.
under 20s left, game tied, LSU ball, going to wait for last shot, TN steals the ball for easy lay up..... LSU throws one in for the tie but couldn't beat the buzzer.
We were 14pt underdogs against #7 TN... so a pretty good showing anyway.
As far as Dale goes.... the man has tons of energy that he exudes......didn't call him "The Great Motivator" for nothing.
We were until we did the stone cold choke in the last minute.
Oh, I was watching it. It came on after the KY game and I got sucked in. Lowest scoring game I've seen in a while. You guys scared the crapp out of TN. Gotta be a moral booster for the team and the new coach. I love the SEC. Nobody's safe.http://grantlogan.net/
I refuse to accept that there are limitations to what we can accomplish. Pete (I am so in love with myself) Draganic
Venting is solely for keeping out as much heat as possible.
You are using about as reflective a roof as possible, with a good, deep insualtion under that--that roof is not likely to be any cooler with a tiny draft of 95-98º+ air under it <g>
Personally, since you are going with a common open space, my inclination is that you might want to put that foam back, under the rafters, to limit any thermal bridging through the ceiling.
It will be an interesting space, and intriguing with that oopen space where the ceiling usually "goes." Which makes me wonder what rafter ties will be in there (top plate of a partition wall not being the best substitute, per se). Now, if I missed where you are putting in timber trusses, then ties are sorted.
With that open space above, remember to design your lights for a "dark sky." Some sort of common fill on a dimmer for the entire ceiling surface works out better. That avoids "hot spots" on the ceiling--which are uncomfortable in the dark, as well as bouncing of the angled surface to where they are needed least.
Sounds fun, share more sketches.Occupational hazard of my occupation not being around (sorry Bubba)
Hi CapnMac,The foam was simply a barrier for the upper side of the cellulose to form a vent space. A number of people including you seem to think the vent space is not going to do much.The open space design was inspired by "The Florida Solar Cracker House" http://www.phys.ufl.edu/~liz/home.html .Structurally, I haven't figured out all the details, but the ridge will have a king beam (not sure this is the proper term) supported by beams from the corners of the house (I don't know the proper term). This puts the top plates in tension. Is this a future nightmare?You mentioned "dark sky". I do plan on indirect lighting of the ceiling by suspending some inverted fluorescent light fixtures to avoid this effect when I don't want it. As I replied to TJK, I'm an amateur astronomer so I'm used to and like dark skys. A few strings of Christmas lights on the ceiling will give me a pseudo starry night :-)I've attached a Sketchup rendering of version 1 of my floor plan. I've made some revisions since but haven't redone the Sketchup model to include the back door and bump out where I show the utility "room" next to the kitchen area.
attached a Sketchup rendering of version
Spiffy. Change to stacking washer-drier and you get hamper/folding space where the other machine was. The entry area is one of those spaces under-defined by too many. I'd actually "roof" it over to reinforce the effect (and have a neat display area above it.
Now, the thing that "annoys" is that "hallway" down the center making a "zone of exclusion." I don't have a good answer for that. Other than, maybe, to turn the kitchen right across that access, divorcing it entirely of exterior walls entire. That's admittedly a radical redesign, though.
(Or you could narrow the dining area to only about 105-115" wide, call it 120" from back of the counter to first furniture, and "gain" more "living room" space.)
Still will probably need something to tie across the width of hte living-dining-kitchen space. Could be tie rods would work, which would not be terribly invasive, visually.Occupational hazard of my occupation not being around (sorry Bubba)
Hi CapnMac,Although not on the original subject "Metal roof System" your comments on the floor plan are greatly appreciated. I don't have a ego too big to preclude reasonable comments.Actually in my latest revision, the washing machine (now a front loader) and dryer has been moved to a bump out behind the kitchen. A rear door has been added. The water heater (blue cylinder) may be eliminated by using a tankless water heater. The bump out (north side) also serves as an airlock for the occasional cold fronts here. Also the French doors next to the main entry has been relocated to the side. Some (maybe all) of the large floor to ceiling windows will be replaced by windows about 60" high starting about 24" above the floor. The original idea was to use standard patio door glass in wood frames.I am not sure how to eliminate the virtual hallway without creating an obstacle course. The rear door will probably become my defacto main entrance. I'm not sure I understand your suggestion to relocate the kitchen.Your suggestion to "roof" over the entry way is intriguing. A display area above it is full of possibilities. My thoughts keep drifting toward a tinted glass/plastic roof over the entry with some sort of artwork above (obviously something visually light weight). Thanks for that suggestion.Making the dining area smaller is simple, just move the sofa back. The placement was determined by my original idea of stoable ladder/stair to a 3rd bedroom loft. That's the purpose of the notch for storage to the left of the entry. I've since reconsidered the placement of the ladder/stairs and size of the loft. I've attached the old rendering to give you an idea of what I was thinking. I'm still working on it.How many tie rods would you suggest? The loft view of the main floor was a consideration. In retrospect, maybe the tie rods disguised by a nice wood covering could be a "feature". Also they could be a place to place the upward facing fluorescent light fixtures for indirect lighting of the ceiling to avoid the "dark sky" effect you pointed out previously. As I replied earlier, I really like the idea of placing some Christmas (LED) light strings permanently on the ceiling for a starry night effect.Thanks again for giving me something to think about the floor plan.-- Teri
I am not sure how to eliminate the virtual hallway without creating an obstacle course. The rear door will probably become my defacto main entrance. I'm not sure I understand your suggestion to relocate the kitchen.
Well, let's see if I can paint with words (rather than have to grab a sharpie, paper, then scan <g>).
Take the rectangle of the public space. Place a rectangle about where the entry is. Place another opposite that for the back door. Set a rectangle between the two for the kitchen. The U-like shape would then overlap into living and dining rectangles turned 90 degrees from how they are now.
Slightly mooted with the new (and very intriguing) loft space now added.
Your suggestion to "roof" over the entry way is intriguing. A display area above it is full of possibilities. My thoughts keep drifting toward a tinted glass/plastic roof over the entry with some sort of artwork above (obviously something visually light weight). Thanks for that suggestion.
Well, my thought was actually to have just enough "roof" to hold a down light or two (and uplighting, too), while also making a point of transition. A person would transition from the very high ceiling, to an intimate space, and then to the ceilingliess outdoors, and vice versa. These spaces can be very important.
Now, with the new sketch, one thing that I see is that if there is any way you can, getting the laundry closet to "mimic" or "mirror" the entry will be to your benefit, if only as a visual "step" that "holds up" the loft visually.
How many tie rods would you suggest?
I really can't, not as a mere hack archy over the internet--that needs a licensed structural engineer (who you need for the frame anyway). That being said, I've seen rods & turnbuckles at spacings from 8' to 18' on center in "single room" structures similar to your present inspiration.
maybe the tie rods disguised by a nice wood covering could be a "feature"
I've always liked the clean purity of the tie rods left alone, but most of my exposure to them was in middling-historic structures where the "bones" were visible anyway.
could be a place to place the upward facing fluorescent light fixtures for indirect lighting of the ceiling to avoid the "dark sky" effect
My experience lighting big flat ceilings is that a cove, with fixtures transversly across the base of the slope works out best. Now, I prefer strip lighting or tubular incandescents for this, mostly for the dimming--that's my preference, though, others' differ.
I really like the idea of placing some Christmas (LED) light strings permanently on the ceiling for a starry night effect
Could be cool. Make sure to use landscape lighting, rather than holiday lighting--lasts longer. Down side of that is dark wires and sockets--but painting to match the ceiling can "cure" that a bit.Occupational hazard of my occupation not being around (sorry Bubba)
Hi CapnMac,Okay, I see your shapie picture now :-) I'll think about it.The loft was planned from the beginning. The rendering I posted is the original and I have changed it some. Originally it overlapped on the master and guest bedroom and I got to thinking the overhang would look a little oppressive hanging over you while laying in bed, so I downsized it to only overlap the closet areas. Originally I was thinking of amoirs instead of built-in closets. The loft was intended for overflow sleeping for the rare occasions of visiting family/friends.I'm still thinking about the utility room. Current design is to place them in a bump out on the rear. I'm not happy with the "tacked on" look though. I'm trying to keep the house small to minimize the property taxes and also satisfy the 1100 sf covenant requirements. I have no need of a McMansion or the money to build one.Regarding the tie rods, I have no problem with showing the "bones". I just don't want a last minute item look. I wonder if a shiny ss cable as ties might add a "modern" look, maybe a grid look? It would be functional too. I could hang holiday decorations on them too :-)I wasn't aware of "landscape" type Christmas light strings. Most people here just put regular one out and replace them when they rot from the weather. I wouldn't have that problem inside of course. I was thinking of using the newer LED types anyway. They should essentially last "forever".You seem to have a good aesthetic sense. I''ll think about the entry way some more. I was more concerned about the basic floor plan when I drew it up. Thanks for the design ideas.-- Teri
I wasn't aware of "landscape" type Christmas light strings.
Yeah, you kind of have to "do" some landscape business to see them. The strings are longer, 200 lamps is short, and they are more expensive, naturally. I got about adecade out of the string of Phillips I used to illuminate my back porch, and even then, about 25-27% of the lamps still tested good when I stripped the string.
When it costs $2-250 per day for a manlift, plus a couple of hands, that's an expense you want to repeat as sledom asa you can. So, there's a market for sturdy, reliable, lighting.
You seem to have a good aesthetic sense.
Hope that's so. Ought to have learned something over the last three decades.Occupational hazard of my occupation not being around (sorry Bubba)
Hi CapnMac,I've reoriented and redrawn the floor plan (attached). Electrons and bits are cheap :-) I also rationalized it to multiples of 4' & 8' (36'x32') which is slightly smaller than the 36'x36' of the original design. The goal was something more than 1100 sq ft per HOA restrictions and the previous design had some unaccounted growth. The reorientation is also to closer match the property logistics of driveway and garage/shop, ie. entry door & side/back door. The garage/shop will be to the west side with the driveway (~E-W) coming in on the N side of the shop and house.I think I addressed your objection of the "exclusion zone" and I found a better access to the loft with a simple pull down ladder/stair. BTW, the best views are to the East and South with the North fair and the West is toward the highway so not so good.I borrowed "The Not So Small House" (Taunton Press) from the library and realized having just the cathedral ceiling over everything would be visually uncomfortable. So I'll think of having some sort defining ceiling dividers between areas. Maybe a "ceiling" grid over the dining area with spot lighting from the entry to the loft overhang dividing the house into zones. My thoughts also included floor color/material to reinforce the zone idea.So, what do you think now?-- Teri
So, what do you think now?
It's neat.
I'd add a 6' deep covered porch down the entire S side, wrap that around the E side (and bump out to 8' for more seating & activity on the "view" side), then bring a 5-6' porch right around to at least the Entry then on the N side. Is does not rain that often in Austin, as you are no doubt aware, but when it does, it's not half-way in the least. Getting a roof over that entry will pay for itself.
Now, my thinking on porches has changed over the years. A few Travis Co projects where rainwater collection was a goal helped that change. So, instead of fussing with posts, piers or the like, my prefered detail is a perimeter beam for porches with a crawlspace beneath. All sorts of benfits from that. Space to stick colllapsible bladders to collect rainwater if that's an issue. Fewer worries for the citified about critters underthe porch deck (also one less place to breed up yellowjackets, too). Also, in 25, 30, 50 years, when the porches are made into living space, that person will be ahead.
Note that in a half-century or so you're gonna get cussed for not having a singe closet in the place <G>
Loft thought--you could set some cabinets against the wall under the loft area. A person could have a set of "curio shelves" that might closely corresponf to ladder rung dimensions, in case you'd like a very subtle access up there.
Oh yeah, you want to reverse the swing on the barthroom and the Guest room doors. The bathroom door especially, as a partially open door will block views from the Living area straight into the bathroom.
You might look at moving the Guest door down to the West end of the wall. Just a thought.Occupational hazard of my occupation not being around (sorry Bubba)
Hi CapnMac,Thank you for the compliment!My house will have a full porch all around with a half Dutch hip roof (Dutch hip on north side only) real traditional Texas style. I plan on it being 8 ft deep for maximal flexibility in arranging the "deck chairs" :-) The east side may get an extended deck with a ramada. Some part of the porch might be screened in for mild weather and the south side may get temporary "glazing" for winter solar gain. Any water on the siding will be minimal even in some of the thunderstorms Texas is infamous for.I had originally planned on a "deck" type porch but the cost put me off. I plan on a grade level porch (if it's still called that) to save on deck material. My plan for the porch deck is to use fiber reinforced cement scored into "tiles". This may get extended into the house flooring for frugality. Water storage for the rainwater collection will be in three 3000 gallon tanks next to the pole barn. I just hope global warming doesn't turn centex into a total desert. As it it, I've noticed we get more cloudy days and nights than I remember in the past.Foundation will be grade beams and piers with 3 courses of surface bonded dry stacked blocks (~24" crawlspace) with a deeper section in the cross area between the bathroom and kitchen. This will also be the storm shelter discussed below.The house will be insulated crawlspace pier and beam with a deeper section for the plumbing parts access (in case). The crawlspace will be the plenum for my heating (and maybe cooling). That way, I will have toasty floors in the winter :-) I like to just wear socks in the winter (okay guys, calm down, I was just referring to my feet :-). The deeper section (4' high or better) will also be a storm shelter with the floor joists doubled up in case a severe storm blows down the house. I may not be in a hurricane zone but we can get some doozies of storms, not to mention tornados (no bets on the roof here).There are built in closets but not overly large. Someone may cuss me anyway in 50 years, but @%$# them :-) I may just make armoires or wardrobes for closet space. Too much closet space would only encourage guest to hang around! Woodworking is also one of my hobbies/avocations. More room just invites storing more stuff. I've decided to overcome my remnants of "afluenza" and simplify. Besides, my pole barn will probably have plenty of junk. My woodworking (future Sawstop, drill press, etc.) and metalworking stuff (lathe, Bridgeport milling machine (to be CNC'd), various welders, bandsaws, etc.) will be bad enough :-)The guest bedroom door swing is a mistake. The powder room door swing is correct. It serves as a warning to me trying to enter from the pocket door from the master bedroom. If a guest is in there with the door open, I'll see it. The pocket door to the toilet and bathtub/shower (I'm leaning toward a shower accessible for someone in a wheelchair) enables someone to use the lavatories in parallel. Leaving the door open is something I'll have to live with, maybe a sliding "in use" sign door lock like the lavatories in airplanes is what I need :-) I said that in jest but it's not a bad idea.The west end of the guest room will have the bottom of the stair/ladder in the way for the door. Again, the loft is overflow accommodations for those agile enough to climb stairs/ladders.I REALLY, REALLY like your suggestion of shelving/nicheos (with back lighting) set in line with the ladder. A really nice touch! I hadn't though of such details, I was more focused on the general plan.-- Teri
I had originally planned on a "deck" type porch but the cost put me off. I plan on a grade level porch (if it's still called that) to save on deck material.
Well, with a wrap-around, by using another "grade beam" edge, you are insulating the "true" foundation wall, with, in your case, an 8' airspace. I've taken to setting that up as a "brick ledge" on the foundation beam, which then aligns to the height needed to frame the porch. Looks funny at the foundation point, like some sort of "keep & bailey" foundation work, but, it is noce at the framing stage.
I just hope global warming doesn't turn centex into a total desert. As it it, I've noticed we get more cloudy days and nights than I remember in the past.
Ah well, it will still be good when the glaciers come again in any event <g>.
stacked blocks (~24" crawlspace) with a deeper section in the cross area between the bathroom and kitchen. This will also be the storm shelter discussed below.
Two things from experience. First, hie yourself off to the texas tech storm shelter site to see their recommendations. While there, note the overhead requirements (nice under-house shelter less-useful if the ceiling above is the floor that flies away with the house.
Second, in the Travis County area, dig a hole on your site to the expected depth plus 1-2 feet, just to be sure that you can. Trust me, it's really really really bad to discover this with the "easy" 80% of the foundation excavation work done.
I may not be in a hurricane zone but we can get some doozies of storms, not to mention tornados (no bets on the roof here).
Nope, but one of the record F5 tornados touched down not that far away from you up in Jarrel.
I REALLY, REALLY like your suggestion of shelving/nicheos (with back lighting) set in line with the ladder. A really nice touch! I hadn't though of such details, I was more focused on the general plan.
Well, I've had to cope with AHJ that would not see reason on "not in the book" spaces. So, there may (I'm neither confirming or denyin) be some spaces where the casework itself is the ladder (or maybe is stepped in height for feline or canine access).Occupational hazard of my occupation not being around (sorry Bubba)
Teri,
I recently installed a 5-V 26 guage galvalume roof here in Florida on a beach house in a 130 MPH wind zone. Our concerns were balancing the seemingly opposing details of hurricane wind resistance and adequate ventilation.
As the person installing the roof, I wanted to use purlins to make it easier to work up there (10/12 pitch) and use that air space as a ventilation source. The problem I see is that you are giving those high wind gusts a place to go underneath your metal roof skin. You are basically building a roof structure that was engineered for 130 MPH winds (engineered trusses and 5/8" plywood) and then lifting the metal roof 1 1/2" above that and asking it to perform the same function on its own with only a single screw every 12" O.C. The plywood sheathing needed ring shanked nails every 4" on its edges to accomplish this. I know that screws are stronger than nails and that the purlins give you thicker material to screw the roof into, but that seems like too big a difference to overcome. I am just looking at this logically, I would love to find a structural engineer or some real tests that have looked at this issue.
We ended up screwing flat to the sheathing every 12" O.C. on the peaks of the V's and every 6" (flats and V's) on the roof edges. We used Titanium (synthetic underlayment - great stuff, I could actually carefully walk up a 10/12) and 2' of Grace at the roof edge, valleys, and unvented ridges.
Our ventilation came from baffles places under the sheathing from eave to ridge. I like your latest detail minus the purlins. If you want a radiant barrier you could use foil backed rigid insulation and/or foil faced plywood sheathing.
Jamie
Hi Jamie,Right now, I'm leaning toward a deck instead of purlins. Your comments and others about the wind pressure getting under the metal to potentially rip it off are pushing me in that direction. I'm a little curious that you think purlins are easier to work on a steep roof. I can see how you use them to brace yourself against them but then you have to be only walking on the rafters unless your 2x's are flat and not on edge as I was originally thinking.SeeYou and others are pushing me toward the snap lock hidden fastener type roofing even though it's significantly more expensive. The appearance of screws isn't the issue with me but potential leaks in the future are my concerns. SeeYou was rather scornful of some claims that hidden fastener roofs are more prone to being ripped off by the wind. I suspect the observations of some were from the fact that the drip edges were not secured to the decking. Since I'm not offended by some screws at the drip edge, that would seem to solve that problem. Your use of Grace I&W at the edge would prevent an annoying and potentially destructive leak behind the facia boards. I'll also have to price out the interlocking metal shingles and see how they compare. I suspect they are more expensive with more labor.I will either use radiant barrier applied under the decking or use the foil covered plywood (Koolply brand here) if I use a vent space under the decking. I'm still pondering if maybe another 1-1/2" or so of cellulose wouldn't be as effective as the radiant barrier and the vent. It would eliminate the extra labor and cost to install baffles offset by the extra cels.Your endorsement of the Titanium (C) underlayment is another check mark among others. I'll have to look up the particulars since I only know it's name from watching an episode of Boob Villa's program. I'm certainly not a luddite, but I wonder about it's long term stability. Plastics in the intense heat here often just become brittle and turn to flakes in a few years even when not exposed to UV.My roof design is to be a hip type with a Dutch hip (half Dutch hip?) on the north side for warm air extraction windows in warm weather so I won't have any valleys to worry about. Some might say my roof will be plain and dull but I sometimes marvel at the elaborate rooflines I see sometimes. Those "fancy" roofs must be costly to build (and reroof later) and much more prone to leaks from all the details which inevitably get overlooked.Thank you for your comments.-- Teri