I’m a cabinetmaker so while I’ve done a bit of roofing before, I’m no expert. My house is almost 30 years old and is on its 2nd 3-tab roof (which I put on about 15 years ago). The garage roof is now leaking like a sieve and asap I plan to at least do the garage section. Because it alredy has 2 layers, I have to strip the old stuff off first. My question involves the decking joints between the rafters. It seems to me that this is where leaks are going to start because when I walk on the roof, the 2 sheets flex apart, potentially breaking the shingles. Is ther a clip or something made that will help hold the 2 edges together? For new work, it seems like it’d be pretty easy to slip the next sheet into an “H” clip or some such. Since I’m not doing new work though, is there an easyish way to lock these edges short of putting up cleats from underneath? Thanks in advance for your help
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what do you have- 1/2" plywood on 24" OC rafters? Sounds cheesy.
do you plan on walking on the roof after the new shingles are installed?
Your plywood sheathing should have a gap between sheets to allow for expansion and contraction- don't go screwing them together with blocking or anything. If the flexing is really bothering you, maybe you could pop out the nails of the sheet near the edge and pull the sheets up enough to get H plywood clips on.
Yep, 1/2"ply, rafters 24"oc. So there IS such a thing as H clips? I thought I made it up.
Taking the plywood up and adding clips would be a PITA. You could add blocking below the joints, but just screw it to the trusses or rafters rather than the sheathing, if you're worried about buckling. I suspect if it hasn't buckled yet, it won't.Birth, school, work, death.....................
http://grantlogan.net/
'H' clips are very difficult to put on after the fact. If it were me, I'd rather install blocking from underneath. Not so bad if there is room to work and you have a nail gun. Plus, it could be done prior to stripping the roof so you wouldn't have to worry about the rain clouds while doing that part of the job.
What everybody else said. H clips are a pain during ply install and esp. after. How much flex is there? You may want to view it from the attic side while someone walks on the roof above. This would give you and idea of how much it is moving. Most roofs flex some espec. 1/2 inch ply on 24" centers. I have worked on jobs with 3/8 inch sheeting........................now that is scary. You may want to do as others said with the blocking or think about using #30 felt instead of #15. That would give you some extra protection. If at all possible don't walk on your roof after install. You should plan your install so as to keep foot traffic to a min. over the newly completed areas. Try to "walk lightly" and do not damage the shingles espec. at the horizonal edges. JMO.........................no charge. Mike L.
Edited 1/6/2006 5:55 pm ET by rooferman
Yes I do have to get on the roof -often. I live in the woods in the seattle area and have to get up there and blow off the cedar droppings and clean out the gutters (I use a leaf blower - don't panic). In the winter this has to be done every 3 weeks or so. So I'd like to solve the problem. But I repeat: There ARE such clips? I just figured there SHOULD be. Where do I get 'em? Are they called "H" clips? The hole-drilling notion occurred to me too. Thanks everyone for your input. What'd we do before the web?
That 30 year old sheathing can't be too happy by now, why not replace it?
5/8" with clips and no more worries.
Joe H
I agree with everyone that it would be a pain in the A to get them in- that's why I'm saying you'd have to pull those nails.
BUT- I was just thinking- if you drill a hole to let the H clip in then tap the H clip over to the middle of the span.
I was thinking the same thing. Drill the hole no lager than you need right next to the truss or rafter. You could repair the hole if you wanted with a small piece of alum or sheet metal under the felt. Use a fastner compatable with the patching metal. Great minds think alike. Mike L.
Yeah, you can drill a hole for the H clips. Could be a little tricky getting them to slide, though.
Or use a saber saw/sawzall to cut about 1" off the edge of one edge of the decking, for a distance of 12-18 inches, then slip a piece of plywood in with a string attached to the center, pull it back up, and fasten with deck screws. Two strings (or one string looped through two holes in the cleat) will help control the orientation of the plywood better.
Before inserting, temporarily tack a short screw in the middle of the cleat, then pry under that with a bar while putting in the first few screws. This will hold the cleat well enough that the screws will "take".
After the cleat's in, tack the cutoff strip back in (if it didn't fall through -- use a screw tacked in it to hold it for the last bit of cutting).
happy?
Ifr I had to walk on the roof that much I would install 5/8 sheathing over the existing 1/2" stagger the seams and forget the clips.
I suspect the flexing is not the cause of the leaks. In my experience leaks rarely occur in the field. Most leaks can be traced to flashings or valleys. If they leak in the field then it's just worn out.
Everyone has given you good advise in my opinion. You have to decide what to do. A sheeting tear-off is alot of work and costly in terms of materials but it would be a LONG TERM fix. Tough to do in bad weather as well. They do sell big blue tarps!!!
Most any lumber yard or even the box stores should carry the clips. I have always called them H clips or ply clips. In your case as existing they would be for 1/2 inch plywood.
Good luck with whatever direction you take. Mike L.
A couple of roofs ago I had trouble develop at the seams, but it wasn't from flexing. Rather, on a cold but sunny day when the sun is shining on one side of the roof it can warm up the attic. This causes the rafters/trusses to expand, but the sheathing on the shady side stays cooler and doesn't expand (especially if there's snow on it). This widens the joints in the sheathing, and if the shingles are getting brittle they'll develop splits along the sheathing joints.Improved ventillation will help prevent this. Plank sheathing would distribute the expansion more evenly and also prevent it. IMO, sheathing should be in roughly 16" wide T&G planks.
If ignorance is bliss why aren't more people
happy?
>> IMO, sheathing should be in roughly 16" wide T&G planks. << Is that a typo or what?
What?
If ignorance is bliss why aren't more people
happy?
>> 16" wide T&G planks. << You actually have 16" wide solid sawn lumber available to you?
Dan------ I don't know if I would go as far as 16"----- but I am right there with you as far as useing real wood
kind of Sad actually---that a lot of these kids now---have never actually used real wood as a sheathing------and if they see an actual knot hole---- oh my---the PANIC !!!!! LOL
Stephen
terry b... you're going to find some rot.. if your roof has been leaking , it's been leaking for a while..
i would strip it and OVERLAY the 1/2" with 3/8" PLY ( not osb ).. and stagger the joints horizontally & vertically
the cost of materials will be offset by not having to try and get some H' clips installed after the factMike Smith Rhode Island : Design / Build / Repair / Restore
Mike, that thought had occurred to me - although I was thinking OSB. (Why NOT OSB by the way?). If I hit it at the right time, it might not cost too much. When I built my cabinet shop 4 years or so ago, I used about 100 sheets or so of OSB @ about $5.00/sheet. Since then, I've seen it oscillate between 10 and 20. Right now I think it's about $15. Hafta keep my eye open.
Thanks for all the good info. Wish I'd known about the clips when I built my shop - same setup. Hafta mark where the trusses are and try to only walk there. Thanks again.
well... i guess OSB would be ok.. especially as an overlay..
we use Advantech, but that's 5/8 and 3/4.. in half inch & 3/8 i'm not much of a fan of OSB.... but for overlay... why not ?
MikeMike Smith Rhode Island : Design / Build / Repair / Restore
Actually, I was thinking of plywood in 16" wide planks.
If ignorance is bliss why aren't more people
happy?
Terry,
I did a 30 year old house about 8 years ago. It had 1/2" plywood which had deteriorated quite a bit, so there were a lot of sections that were soft enough to require patching. 1/2" in good shape is okay, but my guess is that you'll have some spongy sections. When you do the tear-off, keep some spray paint so that you can paint those sections so you won't walk on them.
Also, if you aren't going to replace the sheathing, you absolutely need a pneumatic roofing nailer to put the new shingles on it. The sheathing will be so bouncy that you can't hand-nail it.
It also seems like you could put a new 1/2" layer on top of the exiting one cheaply and easily.