Hi,

I am installing hardwood floor over crawlspace on the wood sub-floor.

I have seen two layers of wood on the floor, the first layers is sold wood strips, and there is particle board as the second.

Should I remove the particle board to install the 3/4 inch solid hardwood floor with cleat nails.

I have also gotten #15 felt (tarpaper) and am wondering if you can provide some help here.

thanks
sm

You have a plank subfloor and particleboard underlayment. The underlayment can be removed to provide a suitable nailing base directly to the subfloor using cleat nails. This should meet the requirements of most manufacturers. IF you need more depth to the floor, or if deflection is excessive without the underlayment, use a plywood underlayment to replace the particleboard. This gives a good structural nailing base for the wood floor. If you nail down plywood, be sure to nail through to joists and use a ring shank nail. For more security use liquid nails subfloors applied in an S-pattern on the plank subfloor, under the plywood as well.

The particleboard underlayment is easiest to remove by cutting it into sections using a circular saw set to the depth of the particleboard, then using a prybar and hammer. Drive the prybar under the smaller squares, and pop them off, then go back for any nails and glue. Do not cut into the subfloor.

15 lb felt is a good selection of vapor barrier to place under the new finished hardwood floor and will prevent moisture from migrating from the crawlspace. Just roll it out and tack it down with the minimum number of staples possible to hold it in place until the floor is laid.

I am planning on using 2 inch cleat nails to nail down the 3/4 inch solid hardwood.

Considering the nail size, would it still be a good thing to remove the particle board. I thought the particle board would provide good insulation and additional moisture barrier. I believe the particle board might be 1/2 inch of less (have to double check).

sm

Using nails long enough to reach the solid subfloor should be fine. I would probably not remove it either. I did remove a 3/4 particleboard underlayment for a kitchen I did, but was not planning on using extra-long nails. Even there, I'm not certain it actually made that much difference.

Read your floor manufacturer warranty to see if it will affect warranty. If not important, or unaffected, leave it. Particleboard provides a very flat underlayment, it just doesn't serve a structural function.

How would you decide on the nail size.

3/4 hardwood
3/8 inch particle board underlayment
1/2 inch plank sub-floor (I think)

Assuming a nail angle of 45 degrees, this is the formula for figuring the lenght of the long side of a triangle (hypotenuse).
C=sqrt(A^2+B^2)
Where A = depth of material
B= horizontal distance of nail at 45 degres
C= length of nail

A: Depth of material: 1/2 + 3/8 + 1/2 = 1.375
(note you nail through the tounge, so only 1/2 for floor).

B: Horizontal distance of nail at 45 degreees = 1.375

C = 1.94: The nail should be 2 inches to penetrate all layers. A 2-1/2 inch nail would emerge too far from the bottom of the subfloor.

Hi Tim,

I like doing things a scientific way. The math you used is neat.

Why did't of think of that? Well, thanks a lot.

thanks
sm