Flat roof pitch?

[Surreycabinetry]

Afternoon guys,

Im building a canopy and wondered what fall/pitch to do the flat roof?

Its 1800 wide, 850 deep.
Lead lined.

I know its 1.60 -1.80 but how much mm to i go up, to get the pitch?

Cheers

 

[Woody2Shoes]

Afternoon guys,

Im building a canopy and wondered what fall/pitch to do the flat roof?

Its 1800 wide, 850 deep.
Lead lined.

I know its 1.60 -1.80 but how much mm to i go up, to get the pitch?

Cheers

My Lead Sheet Association bible says that the minimum fall for a flat roof is 1 in 80

Is your fall along the long dimension?

What thickness are you using (I wouldn't go below code 5)? It looks like you'll need two bays (max spacing of joints with the fall is 600 on code 5).

Cheers, W2S

PS You could just about get away with a single bay at code 6 (1800 X 840 max) - subject to exposure and other caveats

 

[MikeG.]

Its 1800 wide, 850 deep.

I know its 1.60 -1.80 but how much mm to i go up, to get the pitch?

The maths is easy. Just read it out in words.........to fall 1 in 80 means the roof falls 1mm for every 80mm along. If the fall is across the short dimension, then 1 in 80 of 850 is 1/80 x 850 = 10.6mm If it is along the long dimension, then 1/80 x 1800 = 22.5mm. I would hesitate to recommend 1 in 80, though, because dimples in the worked lead can retain puddles when the roof is as fleet as that. I'd be happier with 1 in 60, which gives falls of 14mm or 30mm for your dimensions.

However, it isn't as simple as that, as W2S has so rightly said. These dimensions require more than one sheet of lead, and lead must be joined at a step (from memory that step has to be 50mm, but do check on that .....I'm busy!) if the join is across a down-slope. If you start getting into Code 6 lead, you're A/ getting very pricey, and B/ in the territory of specialist lead workers.

 

[Woody2Shoes]

Its 1800 wide, 850 deep.

I know its 1.60 -1.80 but how much mm to i go up, to get the pitch?

....... dimples in the worked lead ......

Dimples? You must be doing it wrong! :lol: :lol: #-o

 

[MikeG.]

Clumsy handling of the sheet, dropped hammer, uneven substrate..........