How to roof this?

I have a steep 10:12 roof that was built running down under a 3:12 roof. Any ideas on how I could roof this would be greatly appreciated. As it is water has been running under the 3:12, into the attic, from the 10:12. roof 2

Thank you,

The sheathing of the 3:12 roof needs to be continued further so it attaches to the 10:12 roof.

Lay a level or a straight 2x4 on the slope of the 3:12 and slide it up until it hits the 10:12. This will show you the plane of the 3:12 and where the top of the sheathing should run into the 10:12. Attach a board to the 10:12 and bridge the gap with plywood. You may need to trim back the existing plywood on the 3:12 so the new plywood will sit on the rafters and be flush to the existing.

Is the 3:12 over heated space? That is pretty shallow pitch for shingles. You’d be better off installing a low slope product (like a modified rolled roofing). If you want to stick to shingles then you should install additional underlayment, like ice and water shield, across the whole thing. Use something like Grace, which has a smooth top as the granulated kinds will stick to the shingles making future repair very hard.

If you use shingles. Because that’s a large pitch change, you should flash the transition with metal, similar to an end wall.


Just run flintlastic and call it a day,shingle on 3/12 is meh

Thank you for your response, sorry I am a bit late getting back to this, just very busy as we have rain coming. Do you mean that the 3:12 and the 10:12 should be flush where they meet, or should the 10:12 hang over the 3:12? Yes, this is over our music room and I am a little concerned about the slope. As I intend to retire here and not sell, I thought I would indeed use grace on the whole lower roof, maybe two layers? I am hoping that will work. Thought about rolled roofing, I am guessing because there are no shingles it’s better for rain (we get a lot of rain).

is flintlastic the same thing as grace ice and water? Looks like a possibility, going to read up on it tonight. Thanks for the heads up!

Yes,2 ply ,base sheet looks like ice water and cap sheet with granules ,self adhering with matching color
Or can torch down with no name brand,much cheaper

I wouldn’t call it the same as Grace, which is an underlayment for shingles. Flintlastic is a two layer system you would use in place of shingles. You have a self-adhered base sheet that goes over the plywood and then a 2nd self-adhered cap sheet that goes over this. If you decking is rough, they recommend a 3-layer system with a nail down base going on before they other two.

The roofs should be flush where they meet. If you used rolled roofing, you would run it on the lower 3:12 roof and at least 12" up the 10:12 roof. Then you would shingle the 10:12, over the top of the rolled roofing. This will give you a watertight transition.

On a low slope, water won’t run off shingles quick enough and can leak into the joints. With this style of rolled roofing, there is much less joints and everything is sealed down.

Here’s some installion videos by Mule Hide, a very similar product:
-nail sheet-
-base sheet-
-cap sheet-
-shingle tie in-

But if you really want a permanent roof that will last the rest of your life, you should consider a standing seam metal roof.

Thank you for the information, this sort of sounds like the liberty system from GAF. I think I do want to go with a rolled system simply because I’d prefer not to mess with it again. Hoping to find a color that matched my shingles. You have been a huge help!

Thanks so much for pointing me in this direction, I appreciate the input and your expertise!

Having looked at the life span of the rolled roofing, this may not be such a good option for me, 8-10 years is what I have been reading. Maybe I can use the Flintlastic two-layer system to make it leek proof and then add shingles rather than the cap sheet.

Using shingles on a low slope in place of a cap sheet is not a good idea at all. I know it looks similar to the stuff you see for cheap at Home Depot and such but flintlastic is not the same as traditional “rolled roofing”. A 3 ply system should have the same lifespan as a standard shingle.

That makes sense, I need to look into it further. Attempting to set my wife up to be honest, not sure I’ll be around in 10 years to re-roof. Additionally, the colors I have seen do not match what I already have. May do shingles, I’ve been reading about architectural vs 3-tab on low sloped roofs. Some say 3-tabs are much better by design allowing for superior water flow. I currently have architectural for the 10:12.

“EPDM Rubber Roofing - Long Lasting with a 50 Year Lifespan” Ever heard of this?

Was going to suggest a 60 mil fully adhered system. By the time you use a self adhered base and cap sheet the price would be close enough to consider. The reason they say 50 year lifespan is it’s been around that long.

The lifespan/warranties on those systems (Flintlastic, etc) are lower than shingles because of the low slope. A shallow pitch is rough on roof coverings. A rolled roof will last just as long as any shingles you could put on there. But either will probably go bad before the rest of the roof does.

If you want a more permanent solution, you’ll need to look at commercial options like EPDM or TPO. These are used all the time on completely flat roofs. Find an installer who knows how to install one properly and you will have a roof that you shouldn’t ever have to worry about again.

I disagree with fox paws.
A well applied modified can outlast a shingle roof.


I’ve seen a few real nice mod jobs, but more IDGAF jobs. It’s all up to the roofer.

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I see, I guess they can be painted also. 25 yeas would do it, 50, the kids can worry about that :slight_smile: I understand the wear is never as long as they claim.

Not sure if i see the pic correctly but wouldn’t just treating it as a wall work? shingling up to the pitch change, attach a long piece of wall flashing at the transition, then start shingling again but start your first course on top of the wall flashing?

(Not my picture)

I’ll see if there is anyone in my area. I am guessing it’s a skilled thing that a layman best not attempt.