Expert: Richard Taylor, AIA - 10/15/2006

Question
I am constructing a 20X24 addition to a 20X30 existing structure. The  has a 5/12  roof pitch.
should I match the roof pitch with the addition or is it ok to change the roof pitch?

I would like to build a loft in the new addition with the 5/12 roof The structure would be about 2ft taller than if I went with a 6/12 pitch  

Answer
RJ - thanks for your question!

If the ridge on the addition is running perpendicular to the existing, then the pitch makes no difference.  As long as the new ridge is below the existing, you should be fine.  Be sure to account for the additional load of the overlay framing of the new roof on top of the existing.

If the addition is an extension of the existing, then you have a couple of issues to consider.  If the pitches are the same and the roofs align, then you'll have to very carefully align the roofs (otherwise you'll see the "break" between the two). You'll also need to carefully weave the new and existing roofing together - unless you replace the entire roof.

Both of the alignment issues will be irrelevant if the new roof is either higher or lower than the existing, since the roof surfaces won't align.  In that case, you'll need to install a rake, soffit, and siding, but it will look better than if you don't perfectly align the roofs.  Might be a little more expensive, though.  And in that case you'll probably be better off making the roofs the same pitch.

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtastudio.com