adding subfloor


Old 07-25-04, 08:18 PM
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Question adding subfloor

I will soon be installing laminate flooring in my kitchen and adjoining family room. The kitchen currently has vinyl floor and the family room has carpet. After pulling back the carpeting, I discovered that an additional 1/4" layer of subfloor was originally installed in the kitchen. In order to have the new flooring flow continuously between the rooms, I will be adding a 1/4" layer of subfloor in the family room. Are there any special procedures or factors that I need to consider in doing this, such as how the new subfloor is aligned with the existing floor, using screws or nails, securing it into the joists, etc. Any info would be appreciated. Thanks.
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Old 07-25-04, 10:23 PM
Join Date: Jul 2004
Location: Chester, IL
Posts: 285
such as how the new subfloor is aligned with the existing floor
Do you mean seams in the old plywood and your new plywood? If so, just try to make sure they are not aligned with each other.

I always use screws and construction adhesive, and yea it's better if you can hit the joists, but if you have 3/4" plywood as the original sub-floor, if you miss a few times it won't hurt anything.

Post back any further questions, etc, and good luck!!
Old 07-26-04, 08:49 AM
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Yeah, I meant the seams in the old subfloor to the new flooring. The original subfloor is 3/4" OSB tongue/groove. I haven't seen 1/4" OSB, so I assumed I would need to use plywood instead. Any particular type of screw that is best to use for this type of application? How about the appropriate length? OK, here's a dumb question, how do I ensure that I'm actually hitting the joists since I can't see them? Do I just find the nail line on the original board and measure about 16 inches over? How generous should I be with the adhesive? These are probably a lot of silly questions, but I tend to overanalyze the details.
Old 07-26-04, 03:20 PM
Join Date: Jul 2004
Location: Chester, IL
Posts: 285
Alot of things are made or lost in the details, and your questions aren't silly unless you don't ask them, and end up spending a bunch of money you don't need to...THAT would be silly

Anyway, yes the only 1/4" I've seen is plywood and (at least here) runs about 8 or 9 bucks a sheet.

Length of screws.....As stated in other threads, I tend to overkill a bit on fasteners, but I don't want sh..hh...htuff coming loose, that said, I'd probably use 2-1/2" decking screws (not drywall screws), they look kinda gold in color from plating.

Glue...If memory serves, I used one tube per 8ftx4ft sheet, but I only had 3 or 4 sheets to lay also.

Finding joists....short of a studfinder...yea a nail line would work if you can see them, or you can drill a small hole(or 2, one at each end of the same joist) in the joist space and measure over to each one from the hole in the basement, and transfer to the upstairs, then to your new plywood. (the 2 holes are because I've never found a house that the joists below were perfectly parallel with the wall above). Don't assume 16" centers, most floors are 24(theoretically) and walls are 16, but I've seen alot that were...22...20...25...27, ok you get the idea, measure to each one and make a "list" of measurements from your drilled holes to each joist(don't forget to add the 3/4" to center).

Hope this back if needed and good luck.

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