Replies

1. 
   Guest_ | Sep 03, 1999 03:01am | #1

   *
   I would forget the purlins and go directly over plywood or OSB. Your roof will have diaphram loads that will not be carried by purlins. You should put felt under the metal, and this cannot be done over purlins. I have, however, left metal exposed underneath at the eaves. This is a nicer finishing touch than plywood and cheaper, easier and more unique than starter board.

1. 
   Guest_ | Sep 03, 1999 04:13am | #2

   *I have to disagree. I would never use OSB for this unless Istripped with 1x4 and screwed to it. String your front and figure your gable overhangs carefully. I like rake and eave covers for extra protection from wind and water. Use butyl seam tape. Do not use silicone, it will eat holes pretty quick. The little foot laps big foot on the panels. need more tips ? >kk

1. 
   Guest_ | Sep 04, 1999 08:32am | #3

   *AaronMy manufacturers don't recommend steel on anything less than 6/12.Haven't done it on trusses because I don't build with trusses, but see others that do and use 2x4 purlins. I strap i rafterswith 1x4 or 1x6 and screw through the ridges, not the pan!!I would never sheath a roof for steel. It defeats one of the biggest cost savings, and is redundant. If worried about span, order heavier guage steel. Ag panels are available in several guages, and profiles.Never had a problem with silicone eating holes. . . use it on all flashings as a precaution. . . no call backs, ever!!!-pm

1. 
   Guest_ | Sep 04, 1999 09:35pm | #4

   *Patrick, I have seen silicone damage on many roofs. It ate through 24 ga. I have put PBR panels on a 2/12 with no leaks. Are you talking about 5v on screw placement? kk

1. 
   Guest_ | Sep 05, 1999 05:16am | #5

   *KKDon't recognize your terminology. The original post referred to Ag. Panels,(raised rib 1/2" - 3/4", simple overlap at edges, various corrugation styles between ribs) which I am most familiar with. I realize that there seems to be many other types of metal roofing products in the States, including locking panel, hidden fastener type that I am not familiar with.Never a prob with silicone used as a backup under flashings:metal to metal, or metal to wood!!!-pm

2. 
   Guest_ | Sep 08, 1999 08:04am | #6

   *I am hoping to build my wood shop next summer and was thinking about using a Structural Insulating Panel (SIP) for the roof, but to minimize the heat load, I am considering puting on a metal roof spaced about 1 or more above the SIP and vented at the eve and the ridge. (It may be northern Oregon, but it still often gets up to 120 F for a couple of weeks each year where I am building in the Columbia Gorge. I am not as concerned about building for the -30 F winter temperatures as at that time I will be hibernating with a hot toddy and sitting on my stove...) I was thinking of using 2x2s for the spacers from the eves to the ridge and possibly metal purlins across these if I need additional reinforcement of the metal roofing accross the roof. (I would guess that I would have to get very heavy steel roofing to hold the weight of walking on it if the spacers just ran parallel to the raised seams - either that or I would have to put the spacers very close together.) Would painting the top of the SIPS give any additional benefit, or perhaps using some of the ruberized roof coatings to allow any condensation to run off without pentrating the top layer of the SIP. Any better and more cost effective ideas???

3. 
   Guest_ | Sep 09, 1999 09:35am | #7

   *CaseySounds good up to a point. Ventilating between might be overkill, don't SIPs have serious R value??Treating the top face of the SIP also seems overkill. OSB has a shiny surface that should shed what little condensation might develop.If you go for the 2x2 purlins, which should be applied b horizontally, consider bug proofing that vented perimeter,with a screen detail. I did something similar on a 'flat' roof some years ago and hid the screened venting detail up under an overhanging Fascia & dentil moulding. Lost in the shadows.-pm

4. 
   Guest_ | Sep 09, 1999 05:03pm | #8

   *Questons/comments for all of you:1. Why is silicone destructive to steel ? Does this also apply to galvalume? I too have used slicone with no apparent problems so I would like to know more. 2. What I have found is that the baked-on paint finish degrades pretty fat when it is exposed to vehicle exhaust and furnace/stove exhaust such as a garage or barn with cars and tractors idling and acid rain around chimney stacks. Also, airborn dust and soil cointainig certain fertilizer products (lime for example) has to be washed off anually.3. Steel on purlins (1 x or 2 x)is smarter idea than screwing into OSB. Condensation and capillary action inevidably sends moisture down the screw shank into the sheathing. This compromises the connection to the sheathing whereas purlins protect the sheathing and are not bound to release the screws or rot at the connection points. This problem is not prevented by neoprene washers or caulking.4. 2X4 purlins are structural and therefore allow the trusses to be spaced farther and the purlins to be spaced more. It also increases the spacing for rafters considerably. OSB sheathing is structural as well and obviates the need for purlins for structural reasons. BUT, if you need a drain plain and insulation cavity (cathedral ceiling), I still don't know how to elimnate roof sheathing unless you insulate the cavity from the outside.5. Steel against OSB or ply, even with felt/tar paper is not going to drain or convect out humidity as well as the space created by structural or non-structural purlins. Steel against sheathing, even with a fabric drain plain like felt will create a capillary sandwich that holds water against your sheathing. A 3/4" airspace using 1x horizontal strapping with a slight grade aross the roof line makes for a down hill channel on upper edge of each purlin/strap so bulk water is eliminated by gravity. 6. If you don't need the sheathing to create a roof cavity for insulation, the trusses with purlins will save money on materials. Check American Wood Preservers Institute for info on pole buildings where they show the structural tables for 2x4 purlins over trusses. You can increase spacing and spans.7. My understanding is that if you have any slope, steel is fine. Board and batten/ pan and ridge steel is pretty strong once its installed and can be walked on with clean and soft soled shoes. If you lay the steel against the roof deck, the loads transfer to the deck. If you use purlins, walk across the screw lines. There should be no need to walk on a steel roof once its installed since little maintenance is needed in a lifetime. Snow loads rarely reach a weight that a properly installed steel roof, even with a low pitch, can't handle. The exception would be wet snow/ice caused by improperly insulated roof in a heated building. Applications of steel are more often on low pitches -- see the many industrial, commercial and agricultural buildings around the country.

5. 
   Guest_ | Sep 09, 1999 09:46pm | #9

   *TeddGood post. Re: Q.1 I have the same question.Q.3- I didn't say so above because of the proposed use of SIPs, but I think solid sheathing under steel is just plain dumb. You lose the biggest cost saving (4x8 sheets vs 1x or 2x on 24"oc), and the biggest labour saving (fast easy install of strapping/purlins & ready made roof ladder).Q.4-re;i drain plane & cathedral type detail.For years I cut & fitted long sheets of Glassclad (compressed f/g board-R4.5/"- with one Tyvek type facer)between each cathedral rafter up against 1x2 that was fastened to the top inside faces of each rafter, thereby creating along with the strapping/purlins on top of the rafters, vertical & horizontal venting for the steel roof. The tyvek type face was installed up, and any joints caused by short lengths were overlapped so as to provide a continuous drain plane from ridge to soffitt. Glassclad has been taken off the market recently, and I have yet to do another cathedral/steel roof so haven't come up with a replacement, although I did see another job, where the guys had covered the rafters with 'housewrap, then strapped for steel over it, I assume for the same reason. That would certainly make scrambling around the roof on the strapping a little less easy, but still possible. Don't know if the housewrap would stay taught enough, or if it would actually do the intended job.Q.7- The type of 'pan and ridge' galvalume that I use (26g, no gaskets, exposed screws through ridge etc) here in Ontario is not recommended on pitches less than 6/12, an imprtant detail for residential applications.A poorly insulated roof will help the snow to melt underneath, and provides perfect lubrication for the rest of the snow to come sliding off onto unsupecting heads. The same phenomenon happens on sunny days! -pm

6. 
   Guest_ | Sep 09, 1999 10:19pm | #10

   *Hi Patrick,What brand of galvalume (or is that the brand name) do you like to use? What do you mean by no gaskets? Do you use a ridge vent?Jim

7. 
   Guest_ | Sep 10, 1999 06:06am | #11

   *Tedd and pm,RE: Q1 I don't know the chemistry but I have seen this in the field.RE: Q7 SM panels can go on 3/12 and more. PBR panels can go 1/12 and more. This is from manufacturer, S.E. Metals.We screw on the flats to purlins and screw seams togetherwith seam tape in between. We get 60+ inches rain a yearhere in La. with no leaks. SM = 3/4" PBR = 1-1/8" ridge heights kk

8. 
   Guest_ | Sep 10, 1999 06:41am | #12

   *JimGalvalume is a generic term for this hybrid product.Here in southern Ontario, my supplier dealt mostly with Preston Steel in Cambridge, but they stopped making roofing products a few years back, so now I have a choice between Vic West, and an Ottawa manufacturer whose name escapes me at the moment. After having read various posts here on Breaktime there appears to be more variety in metal roofing products in the States, some of which feature hidden fastening systems and gaskets.In the past I have used continuous ridge vents in combination with continuous sofitt vents. . . but thanks to logical info picked up here on Breaktime I am rethinking the whole attic insulation/ventilation scenario. But there's more to it than just i not venting,various other important details must be strictly adhered to, and building codes have yet to catch up with most of this "new" thinking! If your interested, check the archives here at breaktime and hunker down fro a long, interesting, fractious read!!-pm

9. 
   Guest_ | Sep 10, 1999 08:05am | #13

   *kkearney - fastening in the flat just seems like asking for trouble, since more water will run there than on the rib. - jb

10. 
    Guest_ | Sep 10, 1999 09:05pm | #14

    *Patrick"fractious" - adjective easily upset or annoyed, bad-tempered and tending to complain.Good word. I've read every post on Breaktime for the last 6 months, so am confused as anyone regarding the venting scenario. Probably will go with the "standard" soffit/ridge vent for my current project (too tired/busy to fight with the county/inspectors). My supplier sells Vicwest, probably will go with it. thanksJimL

11. 
    Guest_ | Sep 10, 1999 10:22pm | #15

    *The thought behind fastening on the flat is that you can get the screws tight. All you have to worry about is squishing the washer too much rather than also worrying about kinking the rib (which can lead to leaks). I think a careful installer can fasten the ribs and get uniform compression, but it is probably easier to get consistent results on the pan. On a steep roof, there probably isn't much difference in performance. swright

12. 
    Guest_ | Sep 14, 1999 05:27am | #16

    *What is the expected life expenctancy of a modern washer installed as you described? Haven't seen a modern style metal roof around here that is old enough to judge durability of fasteners, but on the old corregated steel roofs on barns, etc., that dot the countryside, after a number of years there is just enough of a remnant of a washer left to indicate that one was originally used. If you stand under one, the roof just slows the rain down and stretches it out... With the recent discussion arguing the the degree to which silicon caulk will damage steel, what is the recommended sealant if one of the washers (gasket?) does spring a leak? Or do you recommend finding the offending screw and replacing it and its washer rather than slathering caulk on all possible culprits?

13. 
    Guest_ | Sep 15, 1999 03:50am | #17

    *Casey,I have a 20 year old roof with good washers. I replace screws, never reuse them. Use Lexel and elastomeric when it is nescesary. I am in the process of restoring a 100 year old house with 12x18 metal shingles. To save these we wire brushed,chemprimed, 3 coats elastomeric with fabric, plus a little Lexel.....................kk

14. 
    Guest_ | Sep 18, 1999 04:47am | #18

    *Check out the cordles drills available now. You can set the clutch so you don't overscrew. The ridge is always a better place to set in steel than the pan since its the ridge that overlaps between sheets. Setting into the pan can draw the joints apart.

15. 
    Guest_ | Sep 29, 1999 10:45pm | #19

    *I will be installing my first metal roof in about 3 weeks. The house has a 12/12 pitch. I'm going to use VicWest or BHP 16" wide concealed fastener panels. I really like Patrick's method of using 1-by or 2-by skip sheathing - big cost/labor savings plus making the roof into a huge ladder is certainly appealing. (Patrick, do you use 30# tarpaper applied vertically under the panels?) I'm going to call the inspector asap about it. But if I do use plywood sheathing, as the roofing manufacturers recommend, how do you guys get around on the roof? Do you use a ladder hooked over the ridge and move it along as you go? Its a long way down. I have a harness and fall arrest ropes etc. Any tips??-jl

16. 
    Guest_ | Sep 30, 1999 03:31am | #20

    *JimI've never used roofing felt under the steel, it sounds like a real pain, but then again I've never used concealed fasteners, or 16" panels either.I think I'd rather chew my own leg off than put steel up on a 12/12 over solid sheathing. See if the panels come in a thicker guage and then you can pass on the ply.-pm

17. 
    Guest_ | Sep 30, 1999 04:50am | #21

    *Jim, I agree with Patrick. Working off of toe boards or roof brackets is uncomfortable.Patrick, RE silicone Two types, One is acid cure(smells like vinager) it is corrosive to metal, the other is not. All I can get at local store is acid type made by Dap.kk

18. 
    Guest_ | Sep 30, 1999 09:38pm | #22

    *I called the county building inspector this morning - said I wanted to use 2x4 horizontal skip sheathing @ 16" on center. He said he would look it up in the UBC and call back. Their interpretation was that it is not allowed in areas of wind-driven snow and roof/ice buildup (chapter 15). He did say that if I could find something else in the UBC that would allow it, they would certainly listen. I'm going to get a copy of the UBC and start reading... Any suggestions on how to convince these people to let me use skip sheathing ? thanks for any help, jim

19. 
    Guest_ | Oct 01, 1999 01:04am | #23

    *JimI can't help you with your UBC, because I'm in Canada. . . but wind driven snow and ice is a fact of life here for at least 4 months of the year and skip vs solid sheathing is not debated on that detail. . . I fail to see the connection.When snow builds up on a metal roof it either absorbs sun heat from above, or building heat from below and melts right at the roof line and slides off. . .Ka woompf. . . look out below!!!You i should own a copy of your code anyway. .. and Gene L. has repeatedly referred to an "alternative building practices" section in your American codes that may provide the argument you're looking for.If no one else comes to your aid here, I'm sure he will help you out if he can, he's a former building inspector in New Hampshire. His email is gleger@access.1.netAt least your inspector sounds reasonable. .. they're not all open to debate.By the way, 2x4 @ 16"oc is overkill. I use 1x5/6 @ 24"oc on 2x8+ rafters @ 24"oc with heavy guage high rib ag type panels!!good luck-pm

20. 
    Guest_ | Oct 01, 1999 08:15am | #24

    *Hey! A case of disappearing post! (maybe I forgot to click on "post" this a.m.) anyway - JimL - I am having a hard time understanding their point about "wind driven snow". Are they sayin' that because of the high wind the skip sheating won't resist "racking" as well as solid sheating? Or that the weight of snow load is too heavy? On a 12:12 roof? I am confused about their thought process here. - jb

21. 
    Guest_ | Oct 01, 1999 11:27am | #25

    *You almost hate to give a guy advice on this stuff. You have to know what your doing is safe. I came down of a roof over twenty years ago and can tell you there are some things that are very hard to do with both arms in casts. Sometimes on steep 1 story roofs a long ladder can be laid on the roof in the same plane as the roof. A ladder next to this one is best used to get on and off the first ladder. I did a 16/12 with 12" ziplock where the eave was 15' above ground and the hill sloped down 6' further where you set up a ladder. I used chicken ladders (the kind that hook over the ridge) for roofing and rock climbing techniques for the horizontal felt installation. This was not OSHA approved but if its my life I'll protect it my way. Joe

22. 
    Guest_ | Oct 01, 1999 11:28am | #26

    *You almost hate to give a guy advice on this stuff. You have to know what your doing is safe. I came down off a roof over twenty years ago and can tell you there are some things that are very hard to do with both arms in casts. Sometimes on steep 1 story roofs a long ladder can be laid on the roof in the same plane as the roof. A ladder next to this one is best used to get on and off the first ladder. I did a 16/12 with 12" ziplock where the eave was 15' above ground and the hill sloped down 6' further where you set up a ladder. I used chicken ladders (the kind that hook over the ridge) for roofing and rock climbing techniques for the horizontal felt installation. This was not OSHA approved but if its my life I'll protect it my way. Joe

23. 
    Guest_ | Oct 01, 1999 04:08pm | #27

    *From what I've read metal roofing should go over skip sheathing (purlins would give the same effect) to allow evaporation of condensation on the underside which otherwise may cause rot. No?

24. 
    Guest_ | Oct 01, 1999 07:31pm | #28

    *Patrick, et al:I was thinking that one of the advantages of the built-in ladder system created by the use of say, 1x6 skip sheathing is that with a metal roof system, you could take advantage of this by working from the top down. Never had any experience installing metal roofs, but very curious to see how it could be done with several large skylights on a saltbox barn roof about 6/12 one side, 8/12 other (longer) side. Anybody recommend this? Seems like it would be a flashing miracle/nightmare.Still trying to figure out what to do with that barn.Scott

25. 
    Guest_ | Oct 01, 1999 07:55pm | #29

    *Jimbo, I'm as confused as you. After I gather some information and get my questions and thoughts together, I'll call them back. I looked at the UBC chapter on roofs. The only reference I could find on skip sheathing was table 15-B-2, "wood shingle or shake application". It does say that in severe climates, solid sheathing is required for wood shakes but not for wood shingles. Their isn't a table or section dealing specifically with metal roofing as far as I could see. Any thoughts anyone? Do any of you use skip sheathing in snow areas? Gene Leger?Thanks for any help. -jl

26. 
    Guest_ | Oct 01, 1999 08:55pm | #30

    *ScottThe last metal roof I did (several years ago)was 6/12 with two skylights and a wood stove chimney penetration. Acknowledging in advance that skylights are pretty but dumb you've got to approach the flashing in a very methodical & scientific manner.The skylight that was spec'd for this job didn't have a model with a raised curb, so I fabricated one out of 2x10. I had a custom flashing fab'd to enclose the curbs. I also fabricated a square chimney chase for the round wood stainless chimney.With raised curbs in place you can then counter flash everything with stock sidewall and endwall flashings from the steel roofing manufacturer. It then becomes a logical progression of overlapping so that downward flowing water passes over and can't get under. The chimney chase was capped off with a stock flat roof i cone flashing, with edges bent over the sidewalls.If by i barn roof you mean "Gambrel", a special flashing is also available for that joint. The roofing panels are put on in two pieces, with the flashing over the lower panel and under the upper panel.pm

27. 
    Guest_ | Oct 02, 1999 02:54am | #31

    *scott,An easier way to do barn roof is with clear panels same profile as metal. Going to install 40 squares next week.kk

28. 
    Guest_ | Oct 02, 1999 03:25am | #32

    *acryllic?

29. 
    Guest_ | Oct 02, 1999 04:07am | #33

    *jb,I think some are acryllic but I like the polycarbonate, these are not like the old fiberglass panels.Did you cut the marble?kk

30. 
    Guest_ | Oct 02, 1999 05:04am | #34

    *yeah, it came out great. Thanks for the help. Polished it to 2000 grit with random orbital sander and automotive body shop paper. Geez, I learned a ton doin' that.Will those clear panels resist scratchin'? Can you walk (carefully) on them? Hey - did you see my question about the term "coon ass"? Is that a blood line, or folks from a certain geographical area? Or what? I used to hear that when I was in the service, but I never did find out what that was about. Is it "coon ass" and "cajun"? What are the differences? (if that wasn't you who used that term, sorry for mistake) - jb

31. 
    Guest_ | Oct 02, 1999 05:25am | #35

    *Jimbobi Coon ass I'll leave alone. ..i Cajunis short/slang for Acadian. . . they were mostly french Canadians from New Brunswick ( up the road from Adrian) who migrated to the states during some hard times when the Brits took over. Acadian itself is probably slang for Canadian. SOB's are everywhere eh???-pm

32. 
    Guest_ | Oct 02, 1999 05:28am | #36

    *jb,Polycarbonate panels don't sratch, dent, and you can walk on them if purlins are spaced correctly.Coonass and cajun are same. They kicked us out of Canada 200 years ago, most moved to La. Lots still speak French down here. Will eat almost anything gator, frog, nutria, rattler ect.kk

33. 
    Guest_ | Oct 02, 1999 08:05pm | #37

    *JimL. Here is the toll free number for ICBO(UBC code).800-425-6587. Caution. ICBO no longer gives free code interpretations. When you call them tell them you do not want an interpretation. You want an explanation as to why the information you need seems to be missing from the code. For starters ask for Dennis McCreary at extension 3410. Again tell him you are not looking for an interpretation, and that Section 1507.8 is of no help. I have no experience with metal roofs and cannot help you.It is a form of roofing I always wanted to do (especially Terne) but never got to do it. By the Bye. There is in the UBC code an Alternative Methods and Materials section. But you must be able to support your argument. GeneL.

34. 
    Guest_ | Oct 03, 1999 08:04am | #38

    *Here's a couple of pics, of the curb detail and the skylight with flashing. This is an experiment to work the bugs out of my scan software, so I may play with it a bit.-pm

35. 
    Guest_ | Oct 03, 1999 09:27am | #39

    *Patrick - Joe - I got all three of them, clear as a bell. - jb

36. 
    Guest_ | Oct 04, 1999 05:01am | #40

    *JBDidja have to load an external viewer first??? That's what I'm trying to bypass. . . seems to be a glitch in my software.-pm

37. 
    Guest_ | Oct 04, 1999 06:11am | #41

    *I'm using Netscape, and, yes, I had to load an external viewer. Rich Beckman

38. 
    Guest_ | Oct 05, 1999 10:06am | #42

    *Patrick - what happens with mine (I have NO idea what I'm "running") is I click and it takes maybe 10 seconds, then I get an all white screen and the word "done" appears in lower left. Then I close that, and a grey box sayin' "script error this page" or something like that. I close that, and the picture comes up. This is how all the rest of the pictures come up on mine too (when I can raise them, usually about 50%). Yours was no problem, but I thought that was a kind of odd looking flange on that skylight. - jb

39. 
    Guest_ | Oct 16, 1999 06:53am | #43

    *Aaron,I've used BHP KlipRib on a place with 9/12, 5/12 and 2/12 roof planes (yes, all on one house). I put 2x4 purlins across 4x10 rafters, 4'o.c., filled with two layers of ridgid insulation, then covered with 30lb. felt and another layer of 1x4 purlins for the hidden mounting brackets. The roof snapped down quickly. No sheathing required. Purlins and a saftey harness made the installation a breeze. That was ten years ago. The roof I've recently installed was their Skyline edition, on ply sheathing at a 4/12 pitch.Dave