New Build Roof Overhang 600mm proposed is it enough?

CaraK

most of the new builds i see these days seem to have designed out any roof overhang.
Whilst i appreciate the uncluttered look no overhang gives i dont like it and had to push Architect at design stage to put in an overhang. Thinking back there didnt seem to be any scientific basis used to arrive at 600mm i was just asked how much do you want. What i wanted was a sufficent width to protect the building from the weather ,that you could stand under if it was raining and to provide some shading from the sun. The 600mm was totally arbitrary.
The carpenter initially couldnt understand it but has come around to it now and is encouraging me to go wider because the external insulation is going to reduce the 600mm to 450mm.

I found a solar shading site that allows you to input your window size and recommends the correct overhang for solar for your location. This is recommending 950mm
Has anybody else done this or got any ideas or suggestions?

Calahonda52

If it is too wide, with a decent slope, the soffit board may be well down below the ceiling line so the EWI need to go up inside the soffit board and meet the roof insulation.
Window shading is best done over the window.
A meter or more of tiles out beyond the birds mouth cut in the rafter might be a bit tricky, especially with the EWI as the chippy may not want to triangulate back to the wall

CaraK

Thanks for replying

no birdsmouth being used the ceiling joist is being extended all the way (so sitting on top of wall plate)and fixed to wall plate with truss hangers

Bonus is the EWI and roof insulation will meet and ensure continous insulation

CaraK

attached is screen grab of the shading calculation. metric measurements

MicktheMan

CaraK wrote: »

Bonus is the EWI and roof insulation will meet and ensure continous insulation

Ewi on timber frame?

CaraK

the first picture is borrowed from internet its exactly what i will be doing

swap timber for single leaf masonary

sydthebeat

planning permission is on the basis of 600mm yes?

CaraK

sydthebeat wrote: »

planning permission is on the basis of 600mm yes?

yeah planning based on drawings submitted which show 600mm

sydthebeat

increasing to 950mm could be considered a significant change which would require permission.

CaraK

sydthebeat wrote: »

increasing to 950mm could be considered a significant change which would require permission.

yes I already contacted them they were okay with it