Flashing over deck gaps?


I’m roofing my house myself. There are a few gaps in the plywood that exceed 1/8", approximately up to 3/8" wide in places. I will be using Dupont Tyvex underlayment with asphalt shingles over. I had the bright idea of covering these wider seems with 4" aluminum flashing as support, nailed only on one edge to allow expansion/contraction. However… Now that I have some strips up I’m having second thoughts. This might address problems created by the wide gaps but I’m curious - will it create other problems? The advice of experienced roofers is greatly appreciated.


3/8 gap is not that big of a deal. You can just shingle right over it, make sure not to nail in the gaps. You can also leave your metal in place just nail both sides securely. I have shingle plank decks over the years with gaps much larger than 3/8 and have never had any problems.


I’m curious as to why you have what looks like a vertical seam that isn’t on a rafter.


Oh man. I wish I could come up with a less embarrassing answer to that question. It made me review requirements. Staggering the sheets I managed to get right. But I missed the fact that H-clips are only for horizontal seams and that verticals should always be cut to the rafters. Hmm. I imagine my solution to that would be to lose the clips, go into the attic and temp-set flush plywood joiners, then back topside to secure them with deck screws. Acceptable?


Cut along rafters and put a piece in (spanning 3 rafters)


2x4 blocking in the attic would work 4 per 4’, but replacing the sheet would be better. H clips defiantly won’t work once the roof heats up, the sheet will curl up.


It’s been a long day. That, plus the senility affect my cognition time to time :wink:

I forgot to mention this is an old open-sheath roof. I did a full tear-off but the 1x4’s are still there. That’s why I decided to run the full sheets! The H-clips on vertical seams I placed for additional support and each is between a 1x4 which spans the rafters. Also there’s a deck screw each end intersection of top deck and 1x4. Like I said, long day today.


Even though you are going over lath you still need to break the horizontal seams on rafters, too many don’t do this and the sheeting pops up later.

If already installed you can screw down the horizontal seams that miss rafters, this is not as good as breaking on the trusses but is adequate.

You don’t need to use H-clips when sheeting over lath either.


Additional question. Did not find specifically mentioned by product instructions, but saw instances in GAF Stormguard YouTube videos where the valley is laid over the eave pieces, as my picture shows I’ve done. But before i call this stage finished I want to verify this is correct. It seems backward to me as water can flow underneath the valley piece. Shouldn’t the horizontal eave Stormguard drain onto the valley Stormguard as all the other underlayment (Tyvek) will?


Keep nails 12" out of center of the valley.


Yes thanks, I got sloppy with that one temp nail. But what about the valley underlayment? Any suggestions there?


Can’t really tell what I am looking at from that picture.