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Discussion Starter #1
So I posted an issue a few weeks back about rerouting vent pipes for a dormer. I will attach some pics but basically I'm going to raise the roof on my ranch and put a few bedrooms upstairs.

Currently I have 2 x 6 ceiling joists and I was going to sister 2 x 10's next to them (my longest unsupported span will be roughly 11-12 feet). I have discovered that there is no sill plate on the top of my stone walls, and each 2 x 6 is just laying directly on top of the stone wall of the house. So my question would be:

Would you just sister the new joist and let it sit on top of the wall ? Or should I cut back the existing 2x 6's enough that I can try to attach a sill to the top of the wall ?

Each has good and bad points from what I see, If I dont use sill plate the new 2 x 10's may not all be at the same level (there will be various heights on the stone wall) but if I cut existing joists to allow a sill plate then I will have to attach that to the rock and I'm worried about cracking the 100 year old stone.
 

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Discussion Starter #3
You know what, excellent point. I guess relying on the stone wall alone (even at close to 14 inches thick) could cause mortar cracks and such. I sure wish we had envisioned putting up an addition when we had the inside of the house stripped to the studs. Previously there were only 2 x 3 studs (almost just firring strips I suppose) that were on the outside walls to house the electric. When I reframed the inner walls I did so with 2 x 4's but dont think I headered off the windows (as that they werent before)

If I want to rely on this framing I guess I would need to remove all drywall and check framing...Or would have to rely on stone which would require engineer I guess

For reference: https://www.diychatroom.com/f19/dormer-need-reroute-vent-pipe-679559/

Such an addition would certainly benefit by the input of a structural engineer. Not that expensive, but worth it just to find out if you can or cannot do it.
 

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retired framer
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The 2x10 doesn't have to be flush with the bottom of the 2x6.

Tack a 2x4 block on each end of the 2x10 flush with the top.

Set it in place with the 2x4s on top of the 2x6. Put a spacer on top of the wall on the inner end and mortar under the other end

If you have to cut some of the 2x10 to miss the stone, the expected cracking won't be a problem because you have it nailed to the 2x6.
 

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Discussion Starter #5
I lookled back through demo photos. Sure enough outer stud walls (on left side of this photo) were not load bearing, because there was roofload only on the rock wall we nailed 2 x 2's onto the 2 x 3 to make the cavity deeper so we could insulate
 

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Discussion Starter #6
Great idea Neal, my only concern now is would the increased weight of the floor cause damage to the stone (cracking and such) the roof weight wont be much different, maybe a little more because I'll go from a 4 pitch to a 12/12 so there will be a bit more on the outer walls

The 2x10 doesn't have to be flush with the bottom of the 2x6.

Tack a 2x4 block on each end of the 2x10 flush with the top.

Set it in place with the 2x4s on top of the 2x6. Put a spacer on top of the wall on the inner end and mortar under the other end

If you have to cut some of the 2x10 to miss the stone, the expected cracking won't be a problem because you have it nailed to the 2x6.
 

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retired framer
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Great idea Neal, my only concern now is would the increased weight of the floor cause damage to the stone (cracking and such) the roof weight wont be much different, maybe a little more because I'll go from a 4 pitch to a 12/12 so there will be a bit more on the outer walls
No experience with stone walls, but i would think it not a big deal.
 

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Not sure what your requirements for permitting in your township are. In mine, you would an an Architect with stamped plans that are approved by the building department.

These sort of questions would get asked to him, as to whether the foundation and the rock wall can sufficently support a dormer.

Looking at what you have, it seems like you have to go on top of the stone as if you're in front of it, you're not picking up the foundation.
 
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