I'd like to get the opinion of all the professional and near-professional builders in here: Would construction adhesives work better to attach corregated aluminum roofing to the underlaying plywood deck?
Im thinking I could use a urethane based adhesive with a couple of nails under the overlap to keep it in place until the adhesive cures. The urethane adhesive stays somewhat flexible (I think) and would allow the roofing to expand/contract a bit with hot/cold cycles without losing its grip
The reason I ask is that the house roof that I put on leaked pretty badly even though I used the roofing nails that have the rubber washer on them, I ended up going up the roof with my caulking gun and putting a bead around every nail head (which took forever) and I would like to avoid a repeat performance.
The roofing would be attached directly to the plywood deck, I cant put any vapor barrier directly under the roofing because the underside of roof is going to be sprayed with polyurethane which is a very good vapor barrier all by itself and I need to give any moisture that gets under the roofing a route to escape.

Would this work? Or is this just yet another idea that doesnt actually work....

Thanks

Dave

-- Dave (AK) (daveh@ecosse.net), June 26, 2000

Answers

A couple of questions from Mr. Sheepish: Did you use roofing felt before? And how about using roofing screws with neoprene washers? They won't pull out like the nails do. A good heavy felt is also good insurance.

The length of the roofing is very important. The longer the roofing, the more it contracts and expands at the ends, creating larger holes that the washer has to cover, which sometimes isn't that well! A long length of roofing will create more problems over time, but not much you can do about it if you have already decided on the roofing material.

Maybe use butyl tape on the roofing seams, or foam side-lap tape. That might prevent wind driven moisture from penetrating your seams. Good luck!

-- Mr. Sheepish (rborgo@gte.net), June 26, 2000.

Mr. Sheepish, Mr McGaugh (Vicki's husband) who has a stainless roof on the house and aluminum on the shop says you are right. You would want to felt the decking then use aluminum nails with neopreen washers, if you use regular nails even with washers your nails will eventually fail. You do not want to have any route of escape for your water, because a properly installed roof even metal would not leak like this. If water was to get under the metal it would rot your decking and travel down your trusses. The whole point of a metal roof is durability, we didn't want to be 70 and up reroofing. Don't skimp now! Vicki and John McGaugh

-- Vicki McGaugh (vickilonesomedoe@hotmail.com), June 27, 2000.

On the house I used a paint-on water vapor permeable membrane called Air-Block from a company called Bakor (or Baktor, something like that) and then nailed the roof to that, I used a paint-on membrane mainly because my roof is steep (its a A frame) and unrolling anything would have been difficult. The roofing sections along the corrugated dimension are only 8 feet long.

So I should have used nails with the neoprene washers on them instead of the ones with the rubber washers.... I wonder why one works better than the other.

-- Dave (AK) (daveh@ecosse.net), June 27, 2000.

Dave, I've used both nails, nails w/washers, and screws w/washers and I find screws w/washers works best. I find you have better control over how deep it attaches when you use screws. I worked in AK up until four years ago, and it seemed most folks had corrugated roofs. Does anyone stock the 'flat tin', the kind with ridges every 12"? I find it's a lot sturdier, but if no one stocks it up there, it's a moot point.

I use to 'seal' my grandma's house every summer for five or six years...she had a corrugated roof, and all the nails eventually disintegrated. Roofing tar'd last until the next big wind storm.

-- phil briggs (phillipbriggs@thenett.com), June 27, 2000.

Phil, I went with the corrugated roofing mainly because a roofing expert at Eagle Hardware strongly recommended it. He said it allows water vapor to escape and keeps the decking from getting soaked and rotting. He told me that what happens is that no matter how well you seal the inside, a little bit of water vapor from the house goes through the roof and when it contacts the cold outside temps it freezes into frost and unless there is a way to let the roof (or wall) breathe, it never dries out.
I cant say if this is gospel truth, but the three other guys there at the time were all nodding heads and I got the same opinion from another friend of mine that does construction.
Resealing a roof every year seems like an awful lot of maintenance, I was hoping to just leave it alone for at least 5 years.

Thanks for all the answers so far! Im no professional just a do-it- yourselfer on a budget.

-- Dave (AK) (daveh@ecosse.net), June 27, 2000.