Hi all. I’ve done a considerable amount of steel,, probably about 70,000 sq ft,, some new,, some old. I’m wondering if anyone can fault my meathod of installing 1×4 over existing shingles on older houses with 1″ sheathing. I generally nail down,, and get the helper to pepper in 3″ or bigger screws on staggered 16-2′ centers. Roofers around here dislike steel for various reasons. Sound,, they say my method is too heavy for existing roof framing (yes,, some old buggers have 2×4 or 2×5 rafters on 32,,then I strap with 2×4) I can’t see any reason to pull old shingles. Leave them where they are,, secondary watershed in case of emergency leakage (unlikely),, like hurricane peels roof off or flashing problems?
I always vent ridge and remove cap singles and allow a breather area at peak of roof by cutting out a vent.
Looking forward to your responses!
Thanks!
dave
Replies
Have done much of the same.
On an old one, a few shims and the furring can really straighten out an old roof. And the cold roof is an added benefit!
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Cold roof? like airspace wise?
I acutally double strapped my story and a half roof,,,, after building out the eaves from 6" to a decent 12" overhang. Double strapping involved 2x2's up the rafters over the shingles screwed in place,, (yes i pre-drilled!) and 1x3?s horizontally on 2'centers. The proof in the pudding was when I was putting the ridge cap on. The steel was hot to touch,, the shingles under it all were cool cool cool. I brag my second floor is as cool as my basement in the summer. not totally true,, but sometimes it is!
d
yes, the airspace creates what is called a cold roof, and helps everything related to climate. less condensation inside, thermal barrier, etc.You really need to look into GRK screws. Fantastic strength and great labor saver
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What are the weight issues?
Does strapping and adding steel decrease the allowable snow load to any extent?
no added weight to speak of, and there is added strength.This install adds less than a pound per foot on a roof that should be designed for forty pounds anyways. Small percentage.
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>>designed for forty pounds anyways
That is twice what our design ground snow load is here, and 25# higher than a quarter mile down the road and across the county line.
The op said he did this on roof with 2x4 rafters, hence the question. Depending on span, I could see itbeing an issue that was just barely adequate to start with.
100 year old rafters. That have done just fine so far!
that's how I've seen it done here. One of the selling points is no tear off.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
If you are running the strapping horizontally, won't that trap any moisture that collects on top of the shingles? And how to you trim the edges to hide the shingles.
"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
No moisture trap and there is trim eave edging large enough to cover that open edge.
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Why does it not trap moisture?"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
First, moisture would have to get in the space. If it can get in, it can also get out the same way. How are you expecting it to get in there?Air can move freely over and through this assembly. You are not caulking and gluing every connection, edge and seam. Where air can move, it can carry water vapour
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The OP said that one reason for leaving the shingles is that they profide a backup membrane in case the steel leaks. I wasn't talking about vapor. If the steel leaks, won;t the horizontal strapping act as a dam?"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
I missed that. I wouldn't be thinking that way. I put a roof on to not leak.A reason for thinking of this as leak protection IMO would be for the term while you are working on the roof. A roof with furring over the asphalt shingles and not finished steel is less likely to leak in an overnight storm than a torn off roof that has only been papered in.
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The secret is double-strapping. See post .3:"Double strapping involved 2x2's up the rafters over the shingles screwed in place,, (yes i pre-drilled!) and 1x3?s horizontally on 2'centers."A true cold roof is supposed to have good, bottom-to-top, chimney-effect airflow. Different folks handle the eave venting differently; everybody uses a ridge vent.AitchKay
I missed the double strapping comment. That would certainly solve the moisture problem that some people here don't seem to be able to get past. Bozos. "Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
O.K fast Eddie. I'm a bozo. I cannot see that condensation and precipitaion and evaporation would aggrivate the strapping directly on the shingles situation. I only cross strap in cathederal ceiling situations. Yes a BIT of moisture could come in contact with the strapping,, but I doubt it's much. But if you have stories/evidence to share,, bring on the citations. (sorry,, caught up in the 'tions.)
dave
No, I was talking about myself. Everyone else said more than once that it wouldn't be a problem, and I kept on with "but...but...but" And then when post 3 was pointed out about the cross strapping, suddenly this bozo saw what everyone else already knew."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Yes but I don't cross strap open attics. So therefore it's not a problem. Kind of like when a witch weighs the same as a duck?
Basically,, when in a cathederal or story and a half situation, I cross strap. Otherwise,, I lay strapping directly on shingles and hope for the best!
Thanks for your imput!
dave
shingles get cut back flush with facia,, matching metal drip edge covers strapping
When doing asphalt/fiberglass shingles over shingles, one concern is relying on the original flashing and just not being able to view the deck for problems.
These may or may not apply to your situation.
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Howard Thurman
Deck issues are real. For sure. We try to be aware of how the fasten fasteners,, paying attention to lack of bite etc. I try to view underside of deck where possible.
Good point however.