I am a homeowner in NJ and we are planning to turn our 1250 sq. ft. ranch into a 1 1/2 story cape style home by adding two bedrooms and a bath upstairs over the main part of the house. I am planning to use TJI Joists for the second floor support, but wanted to “raise” them slightly to avoid damage to the first floor ceiling. I am planning a complete first floor renovation, so I am not concerned about slight cracks etc., but we need to live on the first floor while the second story addition is completed. Any advice on the proper way to “shim” the TJI Joists above the 1st floor plates would be greatly appreciated.
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y ou could install two plates(3 inchs), that could let the new joists clear any cieling boxes, (lights), and wires going through the existing cieling joists, for a stairwell header, or header around chimney, you'll probably have to notch a couple existing joists on the top, and you'll have to hang them somehow from the new header. I don't know how your house is built, these could end up being pieces install between existing cieling joists. Here in no va, I've only popped the top's of brick ranchers( all masonry, these have a 2x8 mudsill on the exterior walls, what we do is cut back the existing cieling joists 3 1/2 ", and install the 2- 2x4's continuos all around, then frame on top of them, centering the new floor joist between the existing.
is your current ceiling and roof framed with trusses or sticks
Excellence is its own reward!
My existing roof is a stick built hip roof with 2 x 8 rafters with 18 inch overhang. The ceiling joists are 2 x 6 and I assume they are sitting on double plates. I do not have access to the "attic" under the hip roof but I plan on cutting a hole in the roof prior to ordering lumber, etc. but want to wait until I have help to demo the old roof and start the framing for the new roof. I have been told that I could pre-cut 1/2" thick plywood shims to place in each bay to raise the new TJI joists above my existing ceiling joists. I am concerned about the long term affects of placing the entire second floor and roof loads onto these shims.
When I added my second story, I added a single 2x4 block on top of the doubled top plate installed new floor joists and 3/4 ply subfloor. I would not use plywood for the spacer only solid wood. To date here in earthquake country, no cracks. You will have to beef up your foundation especially under interior walls that will pick up more second floor load.
Tom
No problem with that. I would use 3/4" though. As someone pointed out, there will be wiring up there to contend with.
The fact that this is a hip framed roof makes it harder tho to do this way all the way up top second roof because the outer two joists will be running into hips and joists all the way at each end. You may have to frame the end walls first and then hang those last couple of joists after the uppr roof is one....
Come to think of it, why not frame all walls without worrying about second floor frame until the shell is clased in? Longer studs and need to let in a ledger for the joists to hang on possibly...
Thinking out loud here and working in the blind but....Hmmmmmmm.
Excellence is its own reward!
I have a similar situation where I'm sistering some upstairs floor joists. The biggest risk to the downstairs ceiling in my case is simple clumsiness. A dropped hammer becomes the "Aw, S###!!" you want to avoid so much. So lay some plywood over the joists as soon as you can, and be careful up there. If the old ceiling is wood lath and plaster, you can toughen it up by squirting ordinary yellow woodworking glue between the lath and the keys. A lot of my plaster wasn't well keyed, and with the old lath shrunken, that helps a lot.
-- J.S.