Roof Design Advice

I’m looking to add a patio roof and would like to get some thoughts on how to tie it into the existing roof. The problem is that it needs to fit within an “inside L”. To make matters more difficult, the existing roof is only 3/12 on the two sides where it will meet the cover. Below is my attempt at a drawing (new roof in blue). I’m open to virtually any design–shed, gable, etc. However, I want to tie the eaves and cornices of the new structure into the existing ones, so I can’t just continue the 3/12 slope further down.

There is only about 7’ of run on the side with the upper wall (light gray roof behind the new cover). By the way, neighborhood covenants limit us to using architectural asphalt shingles.

The longest side (width) of the cover will be approx 31’. Short side (depth) is approx. 13’.

By the way, during heavy rains, a LOT of water runs into the existing valley where the two 3/12 roofs meet–one-fourth of the upper roof and the area to the left. (The upper roof is actually hipped, not gabled as drawn).

This has me stumped, so I’d be really grateful for any suggestions.


what are the adjacent red wall heights?

10’-8" from the edge of the roof decking to the patio floor.

You’re going to have to design a shed roof for that. To get clearance and a decent pitch you’ll have to go to a single ply. What are the dimensions of the patio including overhangs?

Thinking about this a little differently… Take a look at the new drawing. If I turn it as shown then the question becomes how to handle where the two roofs meet (red arrows). The facing fascia boards would both have gutters and I could fashion a sheet metal tent ("^" shaped) to bridge them, forcing water into one or the other. Is there anything wrong with this approach? Is there a better way?

Thanks again

Running a lot of water there. I’d shed roof it off the main house, or frame in a 1’wide gutter and line it with EPDM.

Maybe I’m not clear on how you’re thinking about the shed. If you mean bring it off the 2nd story roof, I think it would be too steep to look right. Plus, there’s that upstairs window on the left to contend with.

If you’re talking about starting higher on the upper yellow wall, that darn window is only 10" above the existing roof. If I started a shed right at the bottom of that window, that would give me a 28" of total drop to the outer edge of the patio roof. At 3/12, I’d only be able to come out about 3 feet further than the existing roof (run on the shed is about 6’). At 2/12, I could come out about 8’ (14’ total run). I was hoping to come out about 13’.

With the gable roof as shown, I can get a 3/12 slope and just miss the bottom corner of the window.

Your suggestion to frame in a wide gutter may be the solution. I haven’t done that before so it never occurred to me. I was just thinking I’d put regular 6" K gutter on both sides and bridge them. Can I assume it’s as straightforward as framing a 12" wide open-top box (sloped for drainage) between the two fascias, lining it with EPDM, and adding downspout?

Really appreciate your help.

If that 3/12 “skirt” is structural and bearing on the lower wall, I’d tie my rafters to the Main wall “skirt” junction. That’d give you a little more run and starting height. EPDM is good with 1/4"/12 pitch. Tie in to the 3/12 on the left and gutter the outside eave. Run a gravel stop drip edge on the right fascia to stop runoff. Any siding contractor can custom break one to your specs. Re-draw the job along those lines and we’ll see how that works.

I think our disconnect is the EPDM. I can’t use it as the visible roof material (the covenants I mentioned in the original post). Architectural shingles are the only approved material.

I guess I’m stuck with figuring out a way to have the two roofs meet on the on the left. Your suggestion of a framed-in EPDM-lined gutter between them sounds like it could be workable.

It won’t be visible on a 1/12 pitch