Roof Overhang

[IEOR00]

Hello,

 

We are building a single storey rear extension 9 X 4m. Our architectural plans are exceptionally light, our fault for going budget. They are silent on how much overhand our roof should have.

 

Could anyone advise how much of an overhang we should have on our flat roof? There is no issue with boundaries. It's a Southeast facing rear extension so we want to maximise sunlight, but protect the windows which span most of the 9m.

 

 

[Conor]

Entirely up to you. Our architect specced no overhang, I increased it to 600mm for some shading, hopefully enough to mitigate need for a brise soleil.

 

How is your drainage designed? E.g. fall back to the valley, or off the sides?

Edited September 3, 2021 by Conor

[Iceverge]

4 hours ago, IEOR00 said:

Hello,

 

We are building a single storey rear extension 9 X 4m. Our architectural plans are exceptionally light, our fault for going budget. They are silent on how much overhand our roof should have.

 

Could anyone advise how much of an overhang we should have on our flat roof? There is no issue with boundaries. It's a Southeast facing rear extension so we want to maximise sunlight, but protect the windows which span most of the 9m.

 

 

 

To protect from the worst of the summer overheating a good rule of thumb is to extend the overhang by 1 ( units unimportant) for every 2  it is above the bottom of the window. 

 

For instance if the overhang is 2m above the bottom of the windows you should overhang by 1m. 

 

It seems like a lot but a nice overhang is excellent all year round. You can stand outside the patio door with a cuppa in the drizzle. See out into the garden in the rain as it won't be drizzling down the windows. Kick off your dirty boots in the dry without messing up the house. Still enjoy the winter as the sun's rays will be much lower.