Framing floor over garage slab

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Old 11-12-10, 03:09 PM
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Question Framing floor over garage slab

Converting an attached garage into bedroom/bathroom/sitting room. Space is 24x24. Raising floor by framing above slab to allow for bathroom drains, to get off cold slab (live in NW Ohio) and to lessen step down from current living space.

Due to ceiling height, I cannot set joists on existing sill, so planned on using ledger boards tapconned and liquid nailed to block foundation to hang joists from. I planned on 3 sections of floor joists tied to two beams that will be in the middle.

Questions: What kind of beam would be recommended? Do I need one 24' beam, or can I laminate 2x8's or 10's to span the 24'. Can I plan on placing concrete blocks on the slab under the beams, every 4-6 feet and then shim to support?
 
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Old 11-12-10, 04:07 PM
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Welcome to the forums! Just how high do you need the floor to be? What is the drop from the living area to the garage floor? Installing a vapor barrier, and sleepers (not fastened to the concrete, but to each other) would make a solid floor without all the beam stuff. If you need the space under the flooring for the pipes, I would set piers along the middle and set a double LVL 9 1'2" beam, and piers along the perimeter where the joists will sit. You won't have good service out of tapcons and joist hangers in block.
 
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Old 11-12-10, 07:50 PM
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Thanks Chandler. I guess drain pipe slope was my ultimate motivation for getting some height off of the slab. I reckon if I ran sleepers in the right direction, I could still get slope for the pipe. My concern was leveling the sleepers and figured it would be easier to make level joists by working from the top of the block wall. But your idea makes better sense.

I have clearance in the middle for the 9 1/2" beam. If I still want the floor raised, it sounds like framing up the floor is the same, but instead of bolting into the block foundation, the perimeter joists and center beam rest on built up piers. Correct?

Can I use 3"-4" thick solid concrete block as piers? What would you recommend I use as shimming materials? Lastly, when you say double LVL 9 1/2" beam, are you saying to bolt two 24' beams together, face to face, for shear strength? Sorry, only limited experience with these beams used as headers at much shorter spans. Thanks again!
 
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Old 11-12-10, 08:47 PM
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These questions should be answered on your plans for this conversion. Egress window is required in the bedroom, footings/stem wall at the old car doors, light, heat and ventilation, do you have a permit? Is the County informed in zoning for the extra load on septic or city sewer? Etc.....

Gary
 
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Old 11-12-10, 09:34 PM
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Thanks Gary. We do not have a residential building inspector in our county, though I do have a township permit for the project - effectively just a tax. Footings and stem wall are in place. A full bath already existed in the garage (though we are moving it 15 feet), so no additional septic load. Existing home heated by EPA wood burning stove, and a small pellet stove will be added if existing stove proves insufficient. Admittedly, our plans are hand-penciled and heavily reliant on our father-in-law neighbor who built the original home and garage with his dad forty years ago.
 
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Old 11-12-10, 10:04 PM
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Glad to hear that! Be sure to dig new piers under the slab for the point loads there. I'll let Chandler carry on........

Gary
 
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Old 11-13-10, 05:07 AM
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The main beam will need further support in for form of piers (depth to be determined by location and zoning rules), as Gary said, but you won't need more than two midspan, IMO in 24' for the main beam. Doubling the LVL can be achieved by using 3" decking type screws. I am not convinced the joisting will need dug piers along the edges. Others may disagree. Now, if you are using contact sleepers, all the piers will go away. This is the best option if you can get your plumbing to work with it. Sharpen your pencil and see if you can get the plumbing to work with contact sleepers. Then we'll go forward.
 
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Old 11-13-10, 06:26 AM
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Thanks to you both for your advice and wisdom. I will be looking at the sleeper option before moving ahead. If I need more slope, I guess I can just go with taller joists ($$).
 
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Old 11-13-10, 07:22 PM
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I meant point loads from the center beam. You can always stud the elevated floor rims down to the sill plate on the blocks. I did one garage conversion, the engineer required a 2' high shear wall at the old car door as we added a new garage also. It kept that end of the floor in shear with it's top being flush with tops of the joists.

Gary
 
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Old 11-15-10, 10:18 AM
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Last edited by texasohio; 11-15-10 at 10:48 AM.
 

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