Hi Folks: I'm living in a bungalo with a 4 square foot hole in the kitchen's ceiling's sheetrock right now. Thanks to the torrential rainfall yesterday. Anyway, it's only a 10ft X 20ft section of the roof that's 'pretty' flat. Let's change that 'pretty'. I just measured the slope to 5" in 10 feet! I guess that's 'too pretty' for pretty shingles. It currently has the 'rolled' shingle variety, with I suspect ordinary felt paper under it. It looks a mess. There are hills and valleys almost an inch high, like it buckled up or something. I can feel water under the shingle, I guess sitting on top of the tar paper where it's not ripped.. Under the tar paper, the roof is entirely 1"X4" slats of wood NOT tongue&groove. The rafters are 24" spaced. Without changing the wood, is there a good chance 'titanium udl' or something like that hold up, with more of our lovely rolled-shingle on top? Thanks! Harry
The lowest allowed pitch I've seen for a shingle application is 1:12 and you're at 1:20 at best. That definitely requires treatment as a flat roof.
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I don't have a clue what 'titanium udl' is but if decking isn't solid, nothing is likely to hold. I'd fix what was wrong w/ the existing decking and re-roof w/ a good flat roof system of your choice. You don't mention whether you're in an area w/ a snow/ice problem or not but that will also be a consideration if you are.
Years ago I built two leans on my garage with a low pitch like you explain. One lean is in the back of the garage, the other in the front. I have a little more pitch but not much more. That was 27 years ago. I have since learned to either use more pitch when I build or to cover the roof with steel roofing. However, that garage roof still stands there with that damn nearly flat roof with that cheap crappy roll roofing, which I have replaced at least 5 times. Twice I had to replace rotted boards from the same sort of problems as you mentioned. Even a few of the 2x4's have rotted and had to be replaced. Last year I replaced the roof on the front of the garage, and this time I did NOT put felt under the rool roofing. I decided to see if NOT using the felt would eliminate the bumps and ripples as you mentioned. Also, it would not hold water between the layers, and be less likely to rot the wood. Whether this was a good or bad idea will show up in a few years when the roofing goes to crap again, and I should note that the modern roll roofing is much thinner than the older stuff was.
Anyhow, I just went on the rear portion of the roof because I noticed some wet spots after the last rain. Sure enough, the whole roof is full of lumps and ridges, some up to an inch high again. Also, the roofing shrunk and in a few spots was exposing the top of the metal drip edges at the ends of the roof.
I have come to the conclusion that the roofing shrinks as it ages. I always leave one inch of roofing extending past the end of the drip edge or boards, and in some places it had shrunk back up to 3/4" (inside) of the drip edge. That means I lost 1 3/4" of roofing, which explains where the bumps come from. I guess it just bakes in the sun and shrinks. That's my only way to explain it.
Anyhow, I found a crack that was leaking, and tarred it. That's when I decided that next summer I am going to replace the whole roof with steel because I am getting real tired of replacing and patching roll roofing. However, to get thru winter, I coated the whole thing with fibered brush on asphalt coating, being sure to cover all the bumps and ridges with a thick coating.
I know there are other options, like rubber roofs, hot tar applications, etc, but when I look at the prices, and the fact that some of that stuff seems to require a professional installer, I think I am better off just using steel roofing and being done with it. The steel is pricey, but I can install it myself, and in all honesty, I think installing steel is easier than the roll roofing, at least on a completely square roof like mine.
Without changingthe wood, is there a good chance 'titanium udl' or something like that
I am better off just using steel roofing and being done with it. The
One more product to look into is Onduline. It's a composite, corrugated sheeting which won't ever need paint and won't discolor. I'm thinking the life expectancy is somewhere in the 20 yr neighborhood.
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