Expert: Dave Johnson - 7/29/2008

Question
QUESTION: I would like to add a screened in porch on my existing patio slab.  I originally was going to tie into the fascia board and run the rafters, however I would not be able to use a 2:12 slope (making sure I use shingles). So now I have to tie into the middle of the roof.  How do I build the addition on top of the existing roof??  Can I do it over the existing shingles??  And how do I fill the gaps on the side that will be created??  Thank you.

ANSWER: hi parker,
make sure the new rafters are hitting the roof directly above the house rafters (for support) when you put the new rafters on, you need to remove some of the shingles and then sheath the new rafters... then when re-shingling, you have to shingle right up under the old roofing.
the sides (gables) will be sheathed and you should paint or put matching siding over.

---------- FOLLOW-UP ----------

QUESTION: "make sure the new rafters are hitting the roof directly above the house rafters (for support)"
How do you recommend attaching the new rafter to the existing rafters?? Do I need to cut back the sheathing??

Answer
Hi Again,
Not necessary to cut away sheathing, just the roofing.
Remember, the critical area will be where you re-shingle into the existing shingles. In fact, if your new rafters are anywhere near the ridge, I'd recommend stripping all the way...

Dave