Cut Roof Design

[Eng33]

In the process of designing an extension to a sixties bungalow. Existing building is a basic box with gables front and rear and the ridge running down it's length. Extension will be to the rear, continuing the existing roof line rearward by 6.5m, and there will be an extension to the side, with it's ridge line perpendicular to the existing (creating two valley's) and ending in a gable end. Existing and new roof construction is purlin and rafter cut roof.

The predicament I have is that because the existing building is 8.1m wide, and the side extension 9m wide (i.e. when viewed from the gable end), the two roofs have different pitches, 32 deg and 30 deg respectively. In terms of roof design and construction, although not the norm, is it still possible to build such a roof? I'm mainly thinking about the fact that the valley rafters won't meet each other on the valley 'ridge' boards. Then there is the issue of roof tiles also not lining up....

Oh, and it's not really possible to make the two building widths the same and the therefore the pitches the same, and the ridge heights both need to be the same too.

I will be constructing the roof myself, so would appreciate the opinions from those experienced in this type of roof construction. Am I worrying about nothing?

Many thanks.

 

[Eng33]

Here's an image of what it is going to look like....

 

[datarebal]

Yes it is easy to construct and tile.
Not sure how handy you are.. but I would say worrying about nothing, A lot of chippies end up with disimilar pitches by accident!!!

or you could simply keep the piches the same and have two little hips coming from the main roof.. But I think the difference might be too small..

 

[^woody^]

Yes it is possible and common, and 2 degrees is a very small amount of difference.

Valley rafters may not, and do not have to meet - they may be different spacings anyway.

You can probably adjust the tile lap to keep the new tiles aligned with the existing

 

[Eng33]

Excellent, thanks for the advice!