Flat roof

[R D S]

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?

[dg]

There is nothing wrong with a flat roof, properly laid and constructed with the correct fall and inspected after 10 years and maintained or replaced as required.

dg

[Phil L]

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.

[noelogara]

they cost much less than the normal roof because they are not slated, they are lower and less dangerous to work on and cheap to cover with chipboard and torched on felt compared to a slated roof which is slow and dangerous work.

[noelogara]

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.

[dg]

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

[The Natural Philosopher]

They can work for a very long time, but then they are not as cheap ;-)

[Dave Plowman (News)]

They're certainly cheap if made like that but not if done correctly.

[Dave Plowman (News)]

I had no option through wanting to extend the usable space in an attic room to the rear outside wall.

[Cicero]

===================== There are alternatives to traditional felt. If you want the benefits of a flat roof without the problems explore the alternatives - e.g. fibre glass, etc.

Cic.

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[Guy King]

The message from The Natural Philosopher contains these words:

Our kitchen projection was done in fibreglass fifteen years ago and is showing no signs of deterioration.