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Do I need a subfloor and why?


Donny Hunt's Avatar
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08-20-16, 06:08 AM   #1  
Do I need a subfloor and why?

I'm about to close in a garage that's apart of my house. I'm wondering if I'll need to build a subfloor on top of my concrete flooring??? Why do I, if so. Thanks for any help!!!

 
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chandler's Avatar
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08-20-16, 06:15 AM   #2  
You don't need to have a subfloor, but it will entirely depend on what you plan on using for a final surface. Fill us in on what you plan on doing with the room, the garage door, etc. Pictures also help.

 
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08-20-16, 06:22 AM   #3  
It would help to know where you live. Is the garage floor level, or sloped?

 
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08-20-16, 08:22 AM   #4  
Most garage floors are sloped to allow water from the cars to drain out the garage door though some are sloped to a floor drain. A floating or subfloor can added to level it.

Most garage floors are lower than the floor inside the house. So, a raised floor deck can be built to raise the elevation to match or get closer to the house elevation.

 
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08-21-16, 06:32 AM   #5  
I live in a very hot part of Texas. The winters are very mild here and it gets dang hot! I want to turn this garage into a bedroom and I'm not real sure on the flooring, probably not real wood and definitely not carpet. The floor is slightly sloped toward the opening. I'm going to remove the garage door and build a wall to close it in. If you look at the picture you'll see how the floor is lower than my house floor. Where the white from the walls ends at the bottom is where my house floors level is. So it looks like my garage floor is about 6 inches lower than my houses.

I think I covered everything, thanks for your help!

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08-21-16, 06:38 AM   #6  
Several factors will enter the picture. If you should raise the floor with sleepers and install a subflooring and final flooring, what will be the height to the ceiling. You don't want a 7' ceiling. In most instances you can raise the floor as the ceiling will be the same height as the house. You could install 2x6 sleepers which would negate the step up into the house somewhat, but you will need to make up for the slope from front to back. Easily done with shims. Installing a band board around the perimeter of the garage (level) will give you a level floor if you follow it with your joists. It will also let you know where to shim it. I would lay in a 6 mil vapor barrier, then the band, then the sleepers. I would not drive fasteners through the vapor barrier. Your Advantech subflooring will tie all the joists together, provided you tightly shimmed them.

 
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08-21-16, 06:54 AM   #7  
A few things... you would likely want to build a sleeper system on the floor to bring the level up closer to existing, as others have mentioned, and to level the floor. Can't say what size that would be, but likely something like 2x6 with 3/4" t&g subfloor. You will need sleepers to level the concrete surface, elevating the 2x6's as needed.

Even if you don't want to raise it up level with existing, a minimum of 1 1/2" sleeper framing would be good... tapered as needed to the lowest area near the garage door.

Being a bedroom, you will need either an exterior door or an egress window (5.7 sq ft free area without any dismantling of the window) as a fire escape.

The exterior walls of your garage and your attic space above may not be insulated.

The lack of heating and cooling ductwork to this area will be something you need to address, as it will still be beastly hot out there if you don't increase your hvac.

Unless you have another bay, or another garage, eliminating the garage will affect the resale value of your home, and necessitates building another garage somewhere on the property at a late date. What I'm getting at is that it may seem to be cheap, convenient floorspace, but the garage is likely already located in the ideal location for a garage.... whereas there might be a better location for a bedroom if you would just add onto the house.

 
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