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Raising Attic Floor for More Insulation

Posted by mcgeebc (My Page) on
Wed, Oct 27, 10 at 12:53

My attic is currently floored with 1" boards. When I bought the house two years ago, there was R-19 fiberglass batts stapled between the rafters. Since the attic is also vented, I realized it wasn't doing much good, so I took the insulation down and layed it on the floor.

My heating/cooling costs are still through the roof, so I am planning to increase the insulation in my attic. I am in Cleveland where code is R-38, so I would like to double it at the least. My attic is also very easy to access for storage purposes, so I would like to keep at least a portion of the attic floored.

My plan is to pull up the current flooring and run 2X8's perpendicular to the floor joists, nailing them in to the rafters. That would give me a total cavity of 14" to reuse my exsisting fiberglass batts and blow in cellulose to top it off. On top of the new 2X8's, I'll screw in a new plywood floor.

Does anyone see an issue with this? I've done some searching online and haven't seen a case of anyone doing this. It seems safe, but my fear is that I can do damage to the structure.

Follow-Up Postings:

RE: Raising Attic Floor for More Insulation

Other than it being quite a bit of work to pull out the boards, install the new supports and then reinstall the board, it seems OK to me.

I'd be careful when banging away on the floor boards and installing the supports to not use too much gusto as you might loosen up the nailing on the ceiling sheetrock?

You might consider just leaving the current boards where they are and install a new raised floor above them with new plywood or boards for the raised floor. Then blow the cellulose between the two floors. This just saves the work of pulling out the old boards, but it requires more material and expense.

Be sure to seal up any wiring, plumbing, light fixture, ... penetrations from the living space tot he attic before you add more insulation -- exfiltration of warm air up into the attic from the living space can be a big heat loss.


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