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Flooring Remodel - Add what layer (Ply/OSB/Particle) to current subfloor.

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May 20, 2013, 09:03 PM
Flooring Remodel - Add what layer (Ply/OSB/Particle) to current subfloor.
Hi, New to site so excuse any lack of information needed.

I need to know:
What layer is best to use on top of a 5/8" Plywood subfloor for installing a floated pre-finished bamboo floor (ply/osb/particle). And how to secure it over existing subfloor (nails or screws). I will likely need to add at least 1/2" of height to match levels of future tile in other places.


Just moved into a home built in '69 in the East San Francisco Bay Area in CA. Wife is going to pop with our first kid any day (really, any day). Carpet in the house was installed in 1996, and everyone said I had to replace it. Bought some bamboo I have worked with before, tore up the carpet in the main and baby's room first...

Subfloor found: 5/8th Ply over 16" joists (crawl-space, not cement-slab house).

Torn-out: carpet/pad in main bedroom, and carpet/pad + vinyl-glued to 3/8" particle board (rooms were different heights).

Time to completion:Need this done immediately, thus need to be able to get whatever the answer is at the local big-box store in the next 24 hours.

Experience level: Novice, but have put in 1 bamboo floor (500 sqft apt), 1 laminate click floor (1400 sqft house). And reasonably successful general handyman for being an engineer in a totally unrelated field (biotech).

Thanks for the help.
May 20, 2013, 11:05 PM
5/8 subfloor is bare minimum and will likely flex too much in-between joists - causing the floating floor joints to pop. Since you need an extra 1/2" anyway, install 1/2" plywood underlayment or 1/2" OSB. It can be nailed or screwed, or a combination of each. If nailed, use a ring-shank so it doesn't pull out. Nails do not have to be long, as you are only going into 5/8". Make sure that you install the top layer so that it doesn't line up with the 5/8 pattern. For 1/2", nails or screws need to be no more than 6" apart in any direction.

The 1/2" layer doesn't have to be a tight, perfect fit as the floating floor can cover a small gap (1/4" or so). You'll need a circular saw for the subfloor. A nailgun or screw gun would be a big help as there will be lots of fasteners - about 150 per 4x8 sheet. Beyond that you probably will be redoing base trim or at the very least adding in shoe molding.

May 22, 2013, 08:57 PM
Thanks JayBee. I went out and got 15/32" plywood sheathing to overlay the current subfloor. But in trying to ensure things were level before i started adding layers, i found some over 3/8" differences in less than 10ft.

Went into the crawl space, to try and trouble shoot why my floors had such a high spot. looks like there are 2x6 joists sitting on top of the 4x6 beams (that are held up by metal rods sunk into concrete spaced every 10 ft or so). The 4x6s are 7 ft apart, and the joists seem to have sunk considerably in the middle.

I wanted to try and float this bamboo, but it looks like there is 3/8" difference between one section of the room, and the max height over the big cross-beams. I have no idea how to compensate for that kind of gap over such a huge portion of the room.

The wife popped the night i posted this, looks like we're using plywood subflooring as floor for a while until I have time to figure out how to lay bamboo planks over a wavy subfloor.

Thanks again.
May 23, 2013, 07:35 PM
Post a picture of what your seeing under this floor.
I've built sheds stronger the what your discribing.

May 23, 2013, 08:59 PM
Yup, sadly you have more going on other than just adding a new floor surface. 2x6 set 7' apart is not going to cut it - your floor joists are too small, that's why you have low spots.

You are going to need some larger joists sistered to the existing ones and perhaps some additional lifting underneath the floor. However, your first step will likely to try to get some sleep - good luck with that!