framing new shed roof & tying it into existing roof

[hotpepperpizza]

Hi. I am planning to build a shed roof over my front door and stoop. It is a ranch house. The shed roof will tie into the existing roof. The existing roof is 5 in 12. The shed roof is 3.5 in 12. The eaves of both roofs will run parallel. The shed roof will extend 4 ft beyond the existing eave.

When I run the rafters from the new beam up to the existing roof (they will intersect about half way up), I wil connect them to a 2x8" plate running parallel with the beam.

Here is my question, when I fasten the 2x8" plate to the existing roof, can I do it right over the asphalt shingles, or must I remove all of the shingles from the area first?

The reason I would like to leave them is because it will likely take me two to three weekends to complete the framing and sheathing, before I am ready to shingle the new roof and tie everything into the existing shingles. My thought is that if I leave the existing roof shingles in place and frame on top of them, that rain will not get into my house during the interim.

Thanks for your help and advice.

[Tom R]

As long as you have only one layer of shingles on there now, - - go ahead and frame right on top of the existing shingles, - - I do it all the time. But run a nice bead of silicone caulk along your 2 X 8 to keep the rain from going under, - - also, - - if it's going to take a few weeks, - - I would install a temporary flashing (diverter) a row or two above to keep off the 'volume'.

[Dragon]

Would it be that much more difficult to take the shed roof to the existing ridge? 3.5 isnt a lot of pitch, and debris (leaves, etc) will tend to collect where the pitch changes, causing water backup.

Also, make sure your existing roof is properly supported where the shed roof is going to tie in.

[Tom R]

Functionally, - - you are correct, - - but aesthetically, - - yuck!! Picture a shed roof coming off the ridge of a ranch house. :shock:

[Sweep]

I would remove the old shingles in order to attach the new work on a smooth deck and be able to find and nail to the old rafters. The original or new building paper should protect the roof well enough. Unless you plan to add new roofing on the entire house it appears to me that leaving the shingles would create a lot of additional work when it comes time to flash into the old roofing.

A shed roof, wherever it hits the existing roof, is not going to add much to the appearance of the house. I would think that it wouldn't be much harder to build a gable roof. In addition to looking better, it would save installing and maintaining trim in that funny side wall triangle and all of the flashing of the wall into the old roof as well as avoiding a gutter over the sidewalk (if that is where the sidewalk is). It would also avoid a 3 1/2 in 12 roof pitch which would require an additional layer of undelayment or a self-adhering waterproof membrane like Ice & Water Shield.

[Tom R]

You're right, Sweep, - - I guess I read his first post too quick, - - I thought he said he was re-shingling the whole roof anyway, - - although I'd still consider leaving them if the job was going to take a few weeks, - - easier to locate a few rafters and 'tie-in' later than to chance a leak and all it's resulting damage.

[hotpepperpizza]

Thanks to all of you who replied to my post. Based on your feedback and others I have talked to, I was planning to put the 2x8 plate right on top of the shingles.

I also like a gable roof better, but this porch is right along side another gable already and having two gables right next to each other wouldn't look right on our house.

This past Friday, I set up a scaffolding along the roof so that I could start building the roof on Saturday. At that point my wife had a change of feelings and didn't want the porch anymore. I wasn't sold on it anyway. Go figure :?

I am used to this kind of thing, so I left the scaffolding up "just in case."

Thanks again.

[dhill]

LOL. If she decides that she does want that porch, buy an awning. Much less work.