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Porch roof a 3:12 pitch - Problem?

Posted by lexmomof3 (My Page) on
Wed, Nov 21, 12 at 13:18

The pitch on our roof over the porch is 3:12. It looks flat to me but I'm sure that without good information why it should be steeper, my husband won't want to change the plan. The plans are already purchased so if we make it steeper, it would have to be something that the builder does by adjusting as he's building. I've read (through another post regarding the dormers) that it should be a 4:12 pitch. Can some please advise? Thanks!

Follow-Up Postings:

RE: Porch roof a 3:12 pitch - Problem?

Yes, it should be 4:12 in order to use shingles like on the rest of the roof (and even so, you'll want the ice-n-water shield on the whole thing).

Now, if it works out to 3.923764:12, you are still okay, but the target should be 4:12 :)

This isn't a big change and should not require new plans. We adjusted the pitch of our porch roof so it looked right and didn't leave a teeny sliver of siding under the windows above it. I mean, our GC did that and he did it on the fly (no extra permits or reviews needed).

I believe the reason for this is that if you don't have the pitch steep enough, then in a hard rain the water can back up the roof and that's why you'd need a solid sheet of roofing material instead of shingles.

RE: Porch roof a 3:12 pitch - Problem?

From the drawing the pitch does look steeper than 3:12
Our porch ended up being 5:12 and had to be decided just prior to building because of the beams needed for porch roof supports. This was literally the last thing framed on the last day of framing. The framers held up the boards to show me. It had more to do with the window sizes and how far off the floor the windows were, and how much trim I wanted to see under the windows.
The 5:12 was just fine. 3:12 would have been too flat for our house. But we would not have been able to tell from drawings.
You can see the house on the Nov "How's your build" thread.

RE: Porch roof a 3:12 pitch - Problem?

It's too flat. And in order to make it steeper, the windows have to move up. They are already too low and in a difficult spot to waterproof. The forward facing gable to the left is also creating a lot of issues with water management as well as being the wrong style cue. The home would function (and look) much better without it and with just the same nested gable as is on the right hand side.

RE: Porch roof a 3:12 pitch - Problem?

Asphalt shingles can be installed over a full layer of Ice & Water Shield at a minimum slope of 2 in 12 but the issue is wind driven rain so it depends on where the project is located.

I'm puzzled why the OP would think anyone would be able to offer sound advice by seeing one artist's rendering of a house. To get good advice specific to your project you should show all plans, all elevations and most importantly a roof plan with slopes noted. A cross section would be very helpful too.

For the fee you are paying for a pre-designed plan set I would not assume the drawings have been properly coordinated or that they meet reasonable or even minimum code standards unless a local design professional has reviewed them. A little care up front can save you a lot of agony later.

RE: Porch roof a 3:12 pitch - Problem?

The house has been built for someone else within the last few years so I'm sure that it passed code. The only plans I have are the very large builder sets. We're in the middle of SC so not much snow but we do get some pretty good wind. Here's a picture of the house as built.

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