DIYbanter - View Single Post

dg

wrote:
Phil L wrote:
R D S wrote:
Are these things dirt cheap to build or what.

With all the horror stories I have no idea why anyone would build a
flat roof.

Can someone enlighten me?

They are cheap.

They don't work for any length of time, but they are cheap :-p

..although, by the time the ceiling underneath has had to be replaced (along
with the flat roof itself) and the whole room decorated half a dozen times,
they're not *that* cheap.

The most common fault in them is that some builders dont put enough of
a fall on them and the water lies in pools if the sun makes the felt
pucker.
If there is a good runoff of water they can last many years trouble
free.
When water lies in pools cracks appear and it seeps in and once it
starts it gets worse every year until you are forced to reroof it.
I like a six inch fall in a 15 foot roof to be sure.

Its freezing/thawing that causes more wear than a hot sun, and
locations subject to sharp changes in temperature caused by sun/shade
cause more expansion/contraction of the felt and premature wear too.

Typically, a leak will develop from a joint. A good few many more years
can be obtained by just resealing the joints.

A 1 deg (1:60) fall is sufficient. The problem with ponding is
generally when the joist spacing is too wide or the deck boards are too
thin, so the weight causes localised sagging.

A proper construction with a low pitch will perform just as good as a
steeper pitch, but obviously a steeper pitch will allow for poor
quality construction.

dg