Roof modification

[EricG]

So last sunday we had a pretty bad hail storm - about quarter to golfball size. A little damage to the car - 80 series wasn't home. Anyway, the insurance adjuster was out yesterday and totalled the asphalt shingle roof.

I live in Black Forest Colorado - you may remember that from the news back in June when 400 homes burned. To close for comfort. In driving through the burn area, I saw very few rubble piles with steel roofing on top, and saw a few steel roofed places standing where everything else was gone. So this looks like a good opportunity to upgrade. The insurance company is picking up the tab for a new asphalt shingle roof, I'll pay the difference for steel.

Still waiting on estimates and such, but I may have a problem. The porch roof on the front of the house is very flat - about a 1/12 pitch. The steel roofing brochures I've read recommend at least a 1.5/12 pitch. A roof over a sun room at the back isn't much better - it's right about 1.5/12

So I'm thinking of building a dormer-style roof out over the existing porch roof - see the sketches below. Any advice on how to frame this, or what it's called so I can search better? I've searched on dormer framing and looked in a framing book I have, but everything I've found so far is for a dormer that goes through the roof to add living space, window, etc., or how to frame this sort of thing on a new roof. I'm just intending for this to sit on top of the existing roof. How would you tie it in to the rest of the structure? Would I need to add anything to the existing interior roof structure (trusses)?

 

[PAToyota]

Done all the time - called a "false dormer" or "faux dormer": http://www.sharedvisions.com/markbuyan/images/Projects/DSC05344-l.jpg

Just lay it out and frame it on top of the sheathing - you're basically building it the same way you would for a real dormer without cutting through the sheathing - although a larger dormer may frame off the floor instead of the roof.

 

[EricG]

Done all the time - called a "false dormer" or "faux dormer": http://www.sharedvisions.com/markbuyan/images/Projects/DSC05344-l.jpg

Just lay it out and frame it on top of the sheathing - you're basically building it the same way you would for a real dormer without cutting through the sheathing - although a larger dormer may frame off the floor instead of the roof.

Yep, that's what I'm looking for - thanks! "false dormer framing" found me this pic, which helps me visualize it alot better. I'm guessing you just nail or lag that 2x6 along the valley into the trusses underneath.

 

[EricG]

I noticed in the pic I posted that they laid it out right over the asphalt shingles ... any thoughts on that? Would definitely simplify things and reduce weather concerns if I didn't have to tear off the existing roof.

 

[snobdds]

Yes, leave on the shingles. No need to take them off. Just another layer of waterproofing.

 

[PAToyota]

I'd advise against leaving the shingles on - for the same reason I advise to strip shingles down to the sheathing when re-shingling even though you're allowed to have two layers. Reason: Makes tracking leaks down a royal pain in the ****...

Strip down to the sheathing and you have a nice flat surface to work on and lay things out. Leaving the shingles on and you're going to have a mess trying to get everything to lay flat and lay things out.

Other question is how you're going to flash the valleys if you have shingles running under your "walls" for the dormer? Water is going to find its way along the tops of the original shingles and under your new framing. If you're dead set on leaving the shingles, at least make those "sills" pressure treated or they are going to rot out in no time...

 

[EricG]

Yea, shingles will definitely come off the rest of the roof - I'm just concerned about the timing between tearing off the shingles, framing the dormer and getting the new roof on. Particularly if I intend to frame out the dormers myself. Was thinking maybe I could lay out the sill plates and cut the shingles out just under those - would reduce the exposure. Or maybe the monsoons will stop soon and it won't be a problem.