raising garage floor 2 feet

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Old 03-08-13, 08:58 PM
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raising garage floor 2 feet

I am planning on converting my garage into a master bedroom with master bath. I want the new space to be at same level as the existing main house floor. I need to raise the floor about 2 feet. My plan is to run a 2x12 stringer around the entire perimeter of the garage and to then run joists across the span. I just don't know what the best way to attach the stringers to cinderblock is. My thought was to use anchors and to place pt 2x4 between stringer and floor to bolster the stringers. Any thoughts or ideas would be greatly appreciated.
 
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Old 03-08-13, 10:34 PM
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Welcome to the forums!

Make all of the wood in contact with concrete pressure treated. You might want to install 1" of foamboard (XPS) against the block first, then attact the stringers through that. I would screw them with Tapcons.
 
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Old 03-09-13, 06:27 AM
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.


Another option is to build a short studded wall along the length of both sides complete with top plate and bottom plate. Then the rim joist and the ends of all the new floor joists will rest on top of that wall so that the carry load is not relying on the attachment to the concrete block. If necessary.....you can even add a third wall down the middle to break up the span and give further support.


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Old 03-09-13, 06:29 AM
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You are probably going to have a 20' span or so, I would guess. You will need support beyond what the cinder block will afford. LVL will be quite expensive to use as floor joists. You may want to consider having custom trusses made with PT bottom chords. That way you could set the trusses directly on the concrete floor over a vapor barrier and build the floor with confidence it won't sag, come loose from the poor cinder block fastening system. You could also run HVAC, plumbing, and electrical before you apply your subflooring. Just a thought.
 
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Old 03-09-13, 07:42 AM
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I built a small apartment in half of my two car attached garage for my father. One winter day he came to the front door and said he couldn't open the door through the garage. Upon inspection, the concrete floor had heaved over an inch from frost. As a garage we would/had never noticed this, but when we build the extra room directly onto the concrete we learned in a hurry.

It's hard to build up from something that was never designed to be the proper starting point.

Bud
 
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Old 03-09-13, 11:56 AM
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I like Halton's plan, for more than just it probably being the most economical. For sure would go with 3 separate stub walls to support floor joists, while breaking the overall span-length in half. Floor joists could be 2 x 8s spaced at 16", with Forest Products span tables showing them good for spanning 11.0' with minimal (L/360) deflection if they're in the mid-E range. Only minimal attachment to the block walls would be required.

A garage conversion I inspected a few years ago (winter-time, heavy snow) in an area of high-end Colorado homes was a classic example of how NOT to do it--the floor felt close to a trampoline when walked across (several tall dressing cabinets wobbled enough to make me think they wanted to tip over), and the room never warmed up during the course of my 3+ hours in the house, even with a dedicated furnace to the room running at full blast. A good vapor barrier on the concrete floor and adequate floor/wall/ceiling insulation are a must.
 
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Old 09-09-13, 03:14 PM
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Thank you all for your ideas. I am leaning toward the 3 short walls and using i joist.
 
 

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