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?
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
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
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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