I am a lurker! I have a problem! I love to read this forum. You guys do some amazing work. I have a question. How do you guys get rafters to fit after you make your calculations and cuts? I find that after I cut the first few on a long building that they seem to change most of the time. I always have someone else check the calculations. I string all the exterior walls and try keep the ridge plumb and level. What is the secret? Timhuler, framer, piffin, dieselpig can you guys help the roof framing challenged?
Thank you.
Luke
Replies
The framers will probably have their own set of instructions for you, but here are the comments of a generalist.
Once you have made the calculations and the cuts, your rafters either fit or they don't. We cut two rafters and try them out in place. If they fit, we use one of them as the pattern for all the rest. If not, back to the drawing board. If we have a non-structural ridge, we use the rafters to set the ridge. If your plates are parallel and level, your ridge will be too. If not, you will have an almost impossible time correcting this. If you have a structural ridge, you will have to calculate the height of the ridge and set this in place first. This gives you slightly less leeway but test your first two rafters anyway, in a couple of places.
You will find that the slightest difference in the width of the building or in the thickness of the ridge will raise or lower the rafters significantly more than that difference. If you can avoid major problems in these areas, keep your rafters identical by using a good pattern, and split the minor discrepancies, you will do fine. At least fine enough.
Make sure your walls are braced plumb.
Schelling has offered you some strong advice.
And FWIW... low pitch rafters will magnify minor discrepencies in the framing around the roof. If your wall to wall measurement is off a 1/4" on a 12 in 12... you may not even notice it in the roof framing. But if you're off by that same 1/4" in a 4 in 12 shed..... look out! You'll be scratching your head all day long.
I can't add much more to what Scell has suggested without knowing more about exactly what doesn't fit right. Is your plumb cut not making full contact with the ridge? Open at the tip or the heel? Or is it not sitting on the wall correctly? Does it all look tight... but the ridge is out of level? Up or down?
See what I mean? It could be lots of things. But double check your math first... that's always the most likely place I've screwed the pooch on something. Then check the wall framing below the roof. Are the wall to wall measurements consistent? Are the walls plumb, level, and square? Are you cuttin' straight? :)
Can you offer up a specific scenario and describe what was 'off'?
try keep the ridge plumb and level
Try?!! You can't just try, you have to succeed....which is impossible.
Let's face it, you are creating a theoretical set of framing members and setting up three points that all have to be perfect. We all know that perfection is a myth, but we still insist on cutting the rafters and expecting them to work. I suspect you've spent a lot of time scratching your head and pondering the mysteries of carpentry.
Long ago, I caved in and decided that I'd rather get done that fight the mysterious spirts that dwell on a rough frame. It is what it is. The reality is that if you think everything will be perfect, then cut a roof member to fit those perfect conditions, it won't fit. Oh, some will fit perfectly, but will the entire run work?
Not on my jobs!
The solution is simple: build in flexibility. Instead of cutting your birdsmouth so every plumb cut snugs up tight, add a little "play" into it. Give the birdsmouth room to slide to and fro and you'll be a lot happier when the roof magically conquers the spirits of the rough frame.
Luke, if you don't want to admit that you aren't perfect, the only other solution will be to order all your frame lumber in the next larger dimensions. Then, take out your jack planes and jointers and start milling your lumber to perfect sizes and eliminate all the crowns and variations that are inherrent in rough frame lumber.
Also, use a sharp knife instead of a pencil.
Or, you can just admit that there are mysteries that can't be solved in rough framing and just carry on....
blue
LOL... that was great. Only thing I could add would be "get a bigger hammer". View Image
Guy's
I really appreciate the responses. Maybe blueeyedevil is correct a frame will not always be perfect, but the pictures I see here look like sculptures. I frame with trusses most of the time because the rafters I cut just pizz me off.
The problem is that no matter what, the plumb cut never looks good to me towards the middle of the ridge. The bottom of the cut seems to lose a 1/16 to a 1/4 in some places.
Luke
is it likely that your ridge is sagging in the middle?
i think most people normally brace the middle to get the correct ridge height
The problem is that no matter what, the plumb cut never looks good to me towards the middle of the ridge. The bottom of the cut seems to lose a 1/16 to a 1/4 in some places.
If everything else is in good shape, I'd bet a gallon of red chalk that much of the 1/16" to 1/4" has to do with your pattern, or lack thereof, how plumb the ridge is, and how straight it stays during the process.
Keep in mind that your boards aren't straight, so cutting the ends perfectly for the pitch, without allowing for the crown will guarantee that you'll get a little gap. A pattern will ensure your cuts are the same since the cut line is independant of the curve of your board.
If you don't keep up with the ridge and how plumb and straight it is, you'll be thinking things are fine, when in fact it's not plumb and your pattern seems to work on one side, when it's really not worth a crap for either since it was cut based on faulty info.
I'd suggest a spool of 80 lb. spiderwire fishing line, some extra time to string the walls and ridge for not only being straight, but at the correct height. The spiderwire strings up flat as glass and is easy to measure from.
You'll find the demons. :-)
I really appreciate all the good advice you guys have given me. I do cut my rafters using a pattern. We use southern yellow pine for our ridge stock and it's usually wavy. Do you guys use 2x stock for your ridges or engineered materials?
"I do cut my rafters using a pattern."
Not sure what you mean by this, but I've seen guys actually use a full rafter as a "pattern" to mark and cut all the rest. The potential for accumulated error is very large. I say rack your rafters upside down (check out some of Tim Uhler's pics of this), snap lines for the ridge cuts and seat cuts. Set your saw to the proper angle, and cut 'em all at once.
Then lay them flat one at a time, and finish the cut (unless of course you have one of those super-cool saws Tim uses!). Use a pattern to get the rest of the ridge cut, and a separate one to get the level leg of the seat-cut. All your dimensions will be right on and will not vary, nor will errors accrue. If your walls are Plumb Level and Square, it will all come together. Use a good blade, and keep it clean (I used to spray mine with silicone to keep the gum from building up).
"he...never charged nothing for his preaching, and it was worth it, too" - Mark Twain
Spiderwire... is that a brand name or a type of fishing line? This sounds like a good tip, can you elaborate a little more?View Image
Spiderwire... is that a brand name or a type of fishing line?
It's a brand of braided fishing line that is about as thin as it gets. The 80 lb. line is about the same as 15 lb. mono. The stuff has very little stretch and is fantastic in the wind or over long distances because of the super thin profile. A concrete contractor back in windy Wyoming turned us on to it and it can be a life saver.
Unfortunately, there are a few things that make this stuff hard to work with. It's so thin that any loose line will turn into a ball of knots--a tiny ball with a zillion knots. We've had ok luck putting it in chalk boxes, but the thin line finds ways to foul the spool.
The stuff is spendy, and 300 yards is something like $40. It is tuff and lasts a long time, if a decent way to store it can be found.
Cheers
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Did you get this months FHB? There is an article about framing gable walls. There is a framer with a 16oz(not titanium) curved claw hammer on his hip.
The sad part is thats the only thing I remember from the entire issue. In the time of chimpanzees I was a monkey.
dustin... like this ?
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Roy & i both carry our Plumbs
Mike Smith Rhode Island : Design / Build / Repair / Restore
Edited 7/24/2006 9:31 pm ET by MikeSmith
Yep.
I carry a 16oz also, but I prefer rip claw. I bought the new version of an old dalluge in April. Before that Craftsman.
After weightloss
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Before I put my toolbelt on the weight loss program.
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Edited 7/24/2006 9:53 pm ET by dustinf
Gawd... I'm embarassed to show my belt now. Yours is just so tidy. You wouldn't believe the crap I find in my belt when I clean it out. Blade wrenches, lags, chunks of plaster, broken pencils, cans of dip, dirty socks, the holy grail.......View Image
I'm border line obsessive about keeping mine cleaned out.
The canvas bag has broken in real nice. It fits like an old pair of Converse All-Stars. Probably the best $9 I've spent all year. The Occidentals are real nice, but heavy as all hell.
Now that I'm working mostly finish I don't need a the heavy duty leather.In the time of chimpanzees I was a monkey.
One of my guys has a pair of those canvas bags and he likes them. They look nice and light and cool in the summer. But he's a speed square dropper. Makes me nuts. I always know where he is or when he's coming because his speed square hits the deck every five minutes.
I've got the green Ocy's... the leather and Cordura ones...I forget what they're called. Lights or something. Anyway, the bags aren't too heavy by themselves. It's all the nails and other crap I carry around in them.View Image
I was having the same problem dropping my speed square. I cut a 2" slot in the pocket so the point of the square would slide in further. In the time of chimpanzees I was a monkey.
That's not a framer's hammer MIke!
It's obvious that you are a brickie!
blue
no... that's my everyday hammer..
my framer is a Stilletto titanium to augment our N88RH'sMike Smith Rhode Island : Design / Build / Repair / Restore
I can't drive a spike worth sh2t with anything less than a 22 oz steel hammer. Titanium's another story, but with steel hammers I really need around 25 oz or so to drive a nail. I bend 'em with anything lighter.... besides those little hammers make me feel like oughta be whispering in the nail's ear to get it to go in. If he get a sinker sunk in two swats with that thing.... God bless him. Too much work for me boss.
The sad part is thats the only thing I remember from the entire issue.
That's just funny, right there. I can relate.View Image
I'm the same way. The past few decks I've done have been all stainless hardware, and the spikes are all hand drive. The Stilletto gets dusted off for the 16d's.In the time of chimpanzees I was a monkey.
The solution is simple: build in flexibility. Instead of cutting your birdsmouth so every plumb cut snugs up tight, add a little "play" into it. Give the birdsmouth room to slide to and fro and you'll be a lot happier when the roof magically conquers the spirits of the rough frame.
I have to agree. There have been times where everything fit just perfect, but I build in some wiggle room.
When you slide a rafter in and out on the plate... won't that change the HAP? Or are we talking a negligible amount of sliding around? Also, we precut our fascia and soffit cuts on our rafters on the ground... so moving 'em in and out won't work at all for us. So that brings me to my next question... do you snap a line to cut your tails? I have such a hard time keeping my fascia straight on long runs when I try to do it this way. What am I messing up? That's why we cut everything before it goes up and just make sure our walls are nice and straight and the fascia line will follow.View Image
We were taught in carpenter school to precut the plumb cuts and leave 1/4" slop.
I make all my cuts level cuts and I have different ways of hanging the fascia now. Because of the level cuts, the rafters/trusses can slide to and fro as much as they want/need. It has sped things up significantly in the fascia straigntening dept.
We also don't pay any attention to the heel when setting trusses or rafters anymore. Our overhangs are already complete and we simply locate the tip of the level cut at the fascia line. The heel is where it is...it's not any more important than the 4' mark of the rafter...or the 8' or the 12'.... The two most important lines are the ridge and the fascia...
blue
I think I understand. I'm still stuck on how your HAP can vary and still not have a bump or dip in the framing.... but I'll keep thinking about it and the light bulb will probably go off soon enough.View Image
Diesel, the fascia line is straight. The ridge is straight. Everything else in between is straight.
All the framing members have variations in their crown and their sizes. That's true no matter what or how you are building. 99.9999% of framers concentrate on getting the tip of the rafter to meet the ridge perfectly. I agree with that. Then, they also insist on the setting the birdsmouth to the outside edge of the wall. That is where we depart. I don't give a hoot about that point, because I believe my fascia line is the governor.
In most instances, the birdsmouth does end up within a 1/4" of the outside of the plate, but when I'm setting the trusses, I concentrate my efforts toward the two tips of the roof. The birdsmouth basically adjusts itself to where it should be.
When you set your rafters, you nail the birds mouth up, then fight to get the tip of the overhang straight. You end up doing that because you don't frame your overhang first, so you don't know where the line is. Your rafters are just floating out in space. That's the difference. I see my fascia line and instantly know if the rafter is flying high or low, east or west, north or south, past the true fascia line.
It's ten times easier.
On this last job we did, the clients wanted a maintenance free overhang. We easily could have run the truss tails out there long, then snapped a line and cut the tails, then added the 2x6 fascia. For me, that's too hard. Instead, we calculated where the overhang should be, build a quick 2xframework and nailed the 2x6 subfascia to it. When we set our trusses, I just lined up the tip of the truss to the outside of the 2x6. On several, the tips were short a half inch. We centered the truss, bringing it in 1/4" on each side. Near the end, the trusses suddenly were hanging over1/2". We centered it, hanging the trusses past the fascia 1/4". My walls were parallel, but there obviously was some variation in the trusses. I could rebuild the trusses, or I can make that simple compromise.
Compromise won out.
To carry the overhangs on these lower pitched roofs (6/12) I added some steel strapping (brick ties). That, along with some serios nailing, especially through the ply edges will hold that overhang up for the next 100 years or so. I'm sure it will outlast the rest of the house.
blue
http://pic9.picturetrail.com/VOL293/2163851/11350387/164188144.jpg
Here's another explanation using Tim's picture.
Tim has set up some racks for his roof cutting technique. Of course, because I'm different, I'd do it different, even if I was doing the same thing. That will make sense in a minue I hope.
Tim is using tgi's and since they are perfectly flat, my difference wouldn't make a difference. BUT....
If we were using dimensional lumber, the placement of the supporting rack WOULD MAKE A DIFFERENCE. I'm assuming that Tim would probably place his support under the heel, just as he has in this picture. I'd put my support as close to fascia as possible.
What's the difference you ask? Well, if thereare variations in the crowns (there always are), then Tim's tip of his projections would wander up and down because of the cantilever effect that he is creating. When he sets his rafter, that same cantilever effect will be transmitted to the overhang on the wall and the battle with the framing spirits will be on! When I set my support on the tip of the rafter, under the fascia line, the cantilevered effect will be eliminated. When I cut my birdsmouth, I essentially would be "scribing" the variations in the crowns and fitting the roof more cleanly to the true fascia and ridge lines. Instead of perfectly cut heels, I'd have small variations that allowed the rafter to nestle into the true plane of the roof using the fascia as one base line and the ridge as the other baseline.
Apply that priniple to the way we do our overhans and maybe you'll understand what is happening to the heels.
Since I've started using this technique, I've significantly reduced the framing demons that used to haunt us when we were getting the overhangs and roof ready for sheathing.
blue
Blue,
When I get back, I'm going to start bugging you for some truss tips. We've got a hip set a week after I get back, and I have to tell you (whispering), I'm looking forward to it :-)
Here is the plan http://www.mascord.com/plan_details.asp?PlanID=1231A&PlanGraphicID=2612&np=true
It's the same one we used the TJI's on and got and extra 1400-1500 sq, a bathroom, bedroom, tons of storage, a kitchenette, and a nice big area for a pool table :-), but when we get back, we will use trusses because it's a custom.
:=)
I'll try an
Tim, your crossing over to the dark side! Once you get started with those trusses, you'll never want to go back.
blue
When you slide a rafter in and out on the plate... won't that change the HAP? Or are we talking a negligible amount of sliding around? Also, we precut our fascia and soffit cuts on our rafters on the ground... so moving 'em in and out won't work at all for us. So that brings me to my next question... do you snap a line to cut your tails? I have such a hard time keeping my fascia straight on long runs when I try to do it this way. What am I messing up? That's why we cut everything before it goes up and just make sure our walls are nice and straight and the fascia line will follow.
Brian, that is what I thought when I first started calculating rafters. Basicall what I figured out is this:
on a straight gable, if all the rafters are identical (cut in the racks they are) and they fit at each gable and the ridge is straight (we string it), then I don't care what small variations there are at the plates. Even though we string the walls and brace them, there are still inconsistencies in the materials, maybe the height of the walls has up to 1/4" differences, etc. But I know that the ridge is straight, and I check the plane of the roof with my eye. Plus I recut my tails in the air to a stringline or even a laser if it's really long run of fascia
http://pic9.picturetrail.com/VOL293/2163851/9645221/140920379.jpg
http://pic9.picturetrail.com/VOL293/2163851/9645221/140920375.jpg
http://pic9.picturetrail.com/VOL293/2163851/9645221/140920369.jpg
I didn't get any pictures of the roof we just wrapped up, but I will when I get back from vacation (I leave tomorrow for 2 weeks :-)). That is the roof we used I-joists on and it turned out so flat its not funny, but we cut the level cuts into the tail and then nailed a block on them and set the rafters to the string. It should work out pretty well.
http://pic9.picturetrail.com/VOL293/2163851/11350387/164188144.jpg
http://pic9.picturetrail.com/VOL293/2163851/11350387/164188803.jpg
http://pic9.picturetrail.com/VOL293/2163851/11350387/164184922.jpg
Me and Kyle flashing westside (framing :-)) http://pic9.picturetrail.com/VOL293/2163851/11350387/166819146.jpg
http://pic9.picturetrail.com/VOL293/2163851/11350387/166824049.jpg
Also, about the soffit cuts. I'll be honest with you, we don't do closed soffits very often although that is starting to change. Some framers across the street from us a year ago May when we did this house http://pic9.picturetrail.com/VOL293/2163851/7273486/96465276.jpg
http://pic9.picturetrail.com/VOL293/2163851/7273486/96465509.jpg they did the one across the street. Anyway, the framer suggested after the tails are cut in the air, run a 2x6 subfascia nice and straight and then using a rafter square against the wall on the house, put a nailer on the wall. The soffit nails to the subfascia and the nailer. Then you don't have to worry about the rafter tail.
" You guys do some amazing work. I have a question. How do you guys get rafters to fit after you make your calculations and cuts? I find that after I cut the first few on a long building that they seem to change most of the time"
I maybe reading more into this then there is.
But it sounds like you are cut rafters A and then that they fit. Then use A as a pattern for B and then B for a pattern for C, etc. Allow an small errors to increase each time.
“I am a lurker! I have a problem! I love to read this forum. You guys do some amazing work. I have a question. How do you guys get rafters to fit after you make your calculations and cuts? I find that after I cut the first few on a long building that they seem to change most of the time.
What is the secret? Timhuler, framer, piffin, dieselpig can you guys help the roof framing challenged?”
I noticed a few things you didn’t mention. First, you said you string all the exterior walls, but are they square? If this is the case, then there will be gaps at the plumb cuts on one side of the ridge, and somewhere around the middle of the rafter run the gaps will switch to the other side.
Second, you mention trying to keep the ridge plumb and level, but you don’t make any mention trying to keep it straight. A string line will reveal any bow, or as already mentioned, sag, that might be affecting the structure.
Finally, third, you didn’t make any mention of assuring the walls were plumb and level. I make this point last, because I figured this would be something you would have already checked first.
Once you’ve built the walls, the ridge must be raised equidistant from the top plates on either side of the rafter run, regardless of whether it’s perfectly level or not. Of course, this will only work if both the long walls run parallel at the same pitch. If they don’t, then you’ve really got problems. From your previous posts however, it sounds like it’s probably something that’s not quite that bad.
On the other hand, if the wall is somewhat out of level, this could also pose a problem. Fore example: If one wall is 3/8” out on one end, and the other end is 3/8” in, your rafters will then have to span a 3/4” difference on either side. In this situation, a pattern won’t work. You’ll have to line up your rafter stock and then snap a line from one end (representing the rafter length for one side of the building), to the other (representing the rafter length for the other side of the building). Then gang cut them. This is much faster than making copies of a pattern anyway.
-T
Divine intervention plays a big role.
What I mean is, think it sweet, cut it sweet, and install it sweet.
Any deviation of the process of sweet, wont be. Be in agreement with what is..then it flows.
Spheramid Enterprises Architectural Woodworks
" I am not an Activist, I am, a Catalyst. I lay around and do nothing, until another ingredient is added"
been spending some time in Andy's teepee hunh?
I had a foreman that built hundreds of houses and his talent was knowing when good enough was good enough.
He would often say, you're not building a f**king piano.
Now I'm on my own and I hired an 18 year old kid. He said he heard someone say, 'You're not building a liquor store.' - which is now my new favorite.
Rough carpentry is awesome. I love it. It's called 'rough' for a reason. I've learned that a quarter of an inch will never be seen from the road.
Granted, it will make the sheetrock, taping, trimming, and painting look better, but sometimes you need to keep moving.
I don't know who's saying it was or exactly what it was but it goes something like....beat it to fit, paint it to match :)
I love this site. Thanks to you all for making my job easier.
Yeras ago I had the same thoughts about the perfect fit of rafters as you. I finally realized that 90 % of the problem was in the lumber itself.To compensate for slightly bowed or different widths of plate framing I simply cut the birdsmouth plumb cut 1/8" more than needed.Then the rafter will hit the top of the ridge ,and the plumb cut will fit tight. If the ridge has a crown, either cut the ridge straight or snap a line and nail to it.I rarely rip the ridge to a straight line, only if the crown is more than 1" in 16'-0"
Sounds to me like you are on the right track. I've always found that 2x plate stock varies in width from 3-1/2" to 3-11/16". This will make a huge difference in the fit of the rafters unless the plates line up on the outside of the wall.I make them line up on the drywall side of the wall for obvious reasons.
Even if the birdsmouth plumb cut is over cut a full inch (which is ridiculous but used for clarity ) it doesn't affect the strength of the rafter.You will have a striaght roof,plumb cuts fit tight and a slightly sloppy birdsmouth plumbcut that won't be seen.
mike