Adding Floor & Living Space to Attic Over Uneven Joists

ziggy138

I'm in the process of remodeling an old schoolhouse. It has a large attic area with the peak of the roof about 20 feet tall. I want to add living space to the attic. Currently there is nothing up there. Building was built from 7 other smaller schoolhouses that were torn down to build the larger one in 1920.

The joists are uneven, different sizes, most are scabbed together to span ~25 feet....so just installing a floor over them won't work. The building has a T-shaped (cross) design inside with an 8 foot wide hallway running down the middle and 7 foot wide rooms perpendicular to this. Here is a floor plan (not to scale) showing the interior walls, which were built with 2 X 5's (actual measurement) - http://munderfschool.blogspot.com/20...loor-plan.html



I would like to add a floor to the attic over the interior walls with some overhang and stay away from the open span of the large rooms (which measure roughly 25 x 30 for reference). I want to add a large wide dormer to the roof on the side with the small rooms. I plan on adding new wider joists (current ones are mostly 2x8's) and want to place the the load on the interior walls. The problem, however, is that the joists go in two directions over these walls, like this...


I would like to add floor to the attic as shown below in pink...


My question is how do I best go about this? It seems that I will need to add the new joists above the current ones, which wouldn't seem to be real difficult, except for the fact that they are not all going in the same direction. Is there a simple way of doing this that I'm not thinking of? If not, what's the difficult way?

Thanks

joecaption

Your going to have to have someone local look this one over. Anyone here will just be guessing.
You also to have to get permits for this work. One for framing and one for electrical.

ziggy138

Got the permits, working on the main floor right now. Was sort of hoping that someone had run into this before or knew of a standard way of doing this, or some product along the line of joist hangers that would help. My guess was to make basically extend the walls up above the old joists and then place new joists on top of the walls.

titanoman

You said something about overhangs and staying away from the larger rooms.
So, the pink area over the big rooms is what you call overhang? Technically cantilevers?
Where the upper walls aren't over the lower walls?
If that's the case, you need new larger joists going the same direction
as what's there, then put your upper walls anywhere you want.

ziggy138

Yeah, cantilevers, sorry. And the pink part isn't really to scale. The hallway is 8 feet wide and the rooms on the right side in the middle are 7 feet wide.

titanoman

You need to joist out the whole floor just like it is (the inspector will probably tell you 12" tji's) and then you can put upper walls anywhere.

ziggy138

So basically set all new joists down beside the existing ones?

How would I deal with the ends where the roof comes down, as 12" ones won't fit?

titanoman

You can cut the angle of the roof off the top of the joist. Doesn't hurt a thing.

ziggy138

Thanks

AndyGump

Hi Ziggy and welcome to the forum.
Could you please tell me how one can get permits for structural renovations like this without having plans?
The plans would detail all of this and would be stamped by the local Building Department.
What is your location?

Thank you.

Andy.

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ziggy138

We had drawings approved, but being a renovation and adding a floor isn't considered a structural change. If this was a new construction, then I would have needed the more detailed plans. I'm in PA.

AndyGump

Hey Ziggy.
As I understand it the state of PA. in now under the UCC Uniform Construction Code for all municipalities. That is based on the 2009 IBC, IRC etc.
At the very lest you should have this additional space designed by a pro so that it would pass the local Building Department regs.
Good luck.

Andy.

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Gary in WA

When cutting the roof slope angle, be sure to leave enough, fig. #7: https://docs.google.com/viewer?a=v&q...RMyCq7zQ737mAg

Leave a "paper trail" with the permit and inspections for your H.O. Insurance carrier, if ever a future claim and when you sell.

Gary

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ziggy138

Thanks for that link, I'll look it over further.

btw - had a friend who had a dryer fire. She's now a statistic and has a couple new rooms and probably higher insurance premiums.

Gary in WA

I hope only a "dryer fire" statistic.... that is scary.

Gary

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