minimum angle required on a flatroof shed to allow rain to run

londonTiger

the_r_sole wrote: »

my cad software shows 1:40 to be around 1.43 degrees!

i take it these measurements mean for every 1 measure vertical there are 40 measurements horizontal. I guess that is a much more efficient way to measure slope angles on a building site as its impossible to use a protractor.



the slope is going to run down the depth of the shed so the slope is going to be across 6ft. I am perfectly happy to lose half a ft in vertical height so the slope I'm going to use is 1:12 which should be far from the minimum and give me a good safety net from bumps in felt and bending timber causing issues down the line

EssexExile

I'd be happier with 1:12 than 1:40 with felt. It'll eliminate the possibility of any pooling at the overlaps or if the underlying timber sags a bit.

RS2000.

londonTiger wrote: »

jsut to be clear I'm not asking for the wall cladding slope. I'm enquiring about the roof slope.

It will be OSB with standard roof felt applied on top.

Are the walls or roof OSB?

I would have hoped you'd clag it.

londonTiger

RS2000. wrote: »

Are the walls or roof OSB?

I would have hoped you'd clag it.

osb is pretty good these days. In my nearest arnold laver (timber merchant) they have a jar of OSB in water. The dater stamp on it is 2012 and it's still intact!!! They use some sort of special resin to glue the strands together which makes it submersible!

RS2000.

londonTiger wrote: »

osb is pretty good these days. In my nearest arnold laver (timber merchant) they have a jar of OSB in water. The dater stamp on it is 2012 and it's still intact!!! They use some sort of special resin to glue the strands together which makes it submersible!

Just doesn't look as good as t&g.

mttylad

For the roof, make one edge about 6" higher than the other & the water will run off just fine. Put a gutter on.

anotherbaldrick

If you have a seam in the roof cladding make sure you seal the seam with the proper mastic before tacking it. Although you may put a good fall on the roof when we get winter storm with heavy winds it will blow the rain back up the slope and through the seam if it is not sealed. Trust me, I have been there.

londonTiger

anotherbaldrick wrote: »

If you have a seam in the roof cladding make sure you seal the seam with the proper mastic before tacking it. Although you may put a good fall on the roof when we get winter storm with heavy winds it will blow the rain back up the slope and through the seam if it is not sealed. Trust me, I have been there.

I went overboard and use bitumous roofing felt adhesive to stuck the felt onto the roof. it was overkill and totally not necessary because the felt actually reacts with the heat and bonds to the roof over time - I still have loads of the adhesive left so I'll probably use the same method.