Thank you for all the replies. It’s a lot of info to take in.
For what it’s worth, the existing “flat” roof (which will remain in place, I see no point of removing it after the gabled roof is built) uses 2x10’s on 16" center, running long ways. Starting at the garage doors, the 2x10’s span 16’, where they are supported by 2 thicknesses of rough-cut 3x12’s which span the 25’ width, supported by a house jack in the center. From there the 2x10’s span another 16’ to an interior wall. On the other side of the wall the 2x10’s span another 10’ or so to the outside wall.
If the bottom of the trusses can’t support significant weight, I could support the bottom of the trusses against the “flat” roof. I’d think it is plenty strong enough.
There’s also the possibility that if you replace the 2ea3x12’s crossbeams with metal beams, maybe you can move those posts to a post against each wall leaving an open garage.
It sounds like you have a LOT of wood up there already. Even if an engineer isn’t required, I’m sure that they would be worth it. Trusses are meant to span from wall to wall, not rest on other lumber. It sounds like you need supporting beams that will allow the existing ceiling to work well as an attic floor.
Thinking about it, you have a built-up roof, right? If so, that’s a lot of weight. The ceiling may already be carrying an attic floor’s load.
Yeah, I agree. Personally, I wouldn’t even consider not removing the old roof. Leaving it on is kind of a kludge, and is going to complicate the project. I also doubt code enforcement is going to allow it.
After rereading this, I realize it might not have been too clear. I could be wrong, but it sounds like the current roof might work well as the attic floor. I’d run it past an engineer, but you may be able to strip the asphalt and rock, trim off the gables and set rafters on the old roof, using the old roof as the new attic floor.
An engineer may want to see additional beams, and you would probably want to add some sort of sheathing or other flooring on top of the old roof sheathing.
Theres a lot of good advice in this thread from 2 weeks ago.
framing a roof is not difficult if you understand how to lay it out with a framing square. The earlier thread has several excellent links that explains the framing square.
Use the right materials. 3/4" plywood exterior grade. Use ring nails Use an underlayment like thick roofing felt (tar paper) and Select a quality shingle. 20 year minimum.
Also, we have a lot of flat roofed homes in my 1950’s subdivision. They are constantly getting patched. Fed up homeowners often have a gable roof erected over the flat roof. Its the one guaranteed method of eliminating leaks.
Get the permit. If you’re spanning 24 feet, you’ll need engineered trusses. Just give the truss company the specifications for the attic storage and they’ll make sure you’re safe. If it’s just a simple gable roof, you’ll be money ahead buying trusses.
“I live in north east PA.” That’s snow country, feet of the stuff is heavy.
This is a very challenging project for a do-it-yourselfer, be prepared and be safe.
I just want to add for the people saying I’d have to use 2x12’s, a house my parents own uses 2x6’s for a span of around 36’ on 20" center with a peak height of over 8’. I wasn’t able to measure the length of the 2x6’s, but they must be pretty damn long.
I will of course build it to code, but apparently 2x6’s are more than capable of spanning 25’.
The 2x12 requirement is for ceiling joists. Your parents’ house has 2x6 rafters that span 18 feet–rafter spans are measured from the ridge to the wall, and the slope of the roof is not a factor.
Also, by code, they would need to use 2x8s if they rebuilt today, but 2x6 rafters may have been allowed in the past. Span tables have become more conservative over the years, partly because the engineers are more cautious and partly because the wood they grow and mill today is pretty crappy compared to lumber from the 1970s or before.
I decided I don’t have time to do the roof myself, so I have a roofing company doing it. They have it framed out and are going to start sheeting it tomorrow. And guess what the building inspector and the contractors agreed on, 2x6 rafters!
