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I am attempting to attach 1/4 inch plywood underlayment (tecply) to 1/2 inch plywood in a bathroom remodel. The
1/2 inch is about 40 yrs. old and is in
pretty rough shape. I have been advised
to nail or screw every 6 inches in the
field and 4 inches at the perimeter.
Does this mean fastening in some places
to the subfloor and joists and only to
the subfloor in others? I have tried
fastening a scrap of the underlayment
to the subfloor with 1 1/4 inch drywall
screws and the screws don’t have enough
grab to countersink their heads into
the underlayment, although they are not
loose. They just spin in the plywood
without drawing tight. I was advised by
some to use a pneumatic stapler, but I
have my doubts as to the ability of the
staples to hold. I will be installing
commercial grade VCT. I think the plywood has seen a bit of water and may
have some delamination. I read a posting by a fellow named Lalonde who
recommends carpet glue and ring shank
nails. Will the ring shank nails stay
put and not pop? Or is there a screw
that will grip better in the plywood?
I tried a particle board screw (aggressive thread) and it did’nt perform any better than the drywall screw.
Any thoughts? – Thanks much -Paul S.
Replies
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Paul, I just stumbled across your post. I use the carpet adhesive for laminating plywood under tile , not for doing what you are doing. You should replace the 1/2" subfloor if it's not in good condition. Once you put that carpet adhesive on something , you will never get the pieces apart. If you want to ever replace the flooring, you will want the 1/4" underlayment to be removable. I personally think adding 1/4" plywood on top of something else is asking for a squeak. It is normally done with a zillion 1/4" crown staples. Screws won't pull down as you found out. I would consider a layer of 15# tarpaper between the layers to prevent squeaks if you use this method.
*Okay, I just did this on my kitchen floor this weekend - and gees, I didn't use felt paper between the layers. My office has the same system over an intact 3/4 floor, no squeaks, lots of traffic. For the remainder of the room which will be a different flooring system to paper or not to paper. Oh yes. Used ring shanked nails, 8" on center and 4-6 on edges. Pneumatic nailer, some countersink, luan 1/4" plywood to even up floor.Dennis
*I agree with LaLonde. I would saw the old floor out before I did anything and start from scratch. If there is a tub, I would be tempted to leave it and rent a flush cut say, place a piece of 1/4" plywood along the tub to prevent chipping and cut parallel to the tub. The rest of the bathroom would come out. I seems these projects never go smoothly, and inevitably you do more than you planned.
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BTW. I tried your carpet adhesive suggestion when building up the kitchen subfloor. It appears to have worked well, and the adhesive was pleasant to work with.
My understanding is the that the second layer should be attached only to the first, not the joists. (I -think- this is what the APA folks recommend.) With adhesive, I used just enough fasteners to hold the wood until the glue dried.
*Mornin' Andrew! I hope your kitchen floor project works well. I have installed well over 50,000 sq. ft. of ceramic tile over laminated plywood and have never had a problem. I am very generous with the screws though! It's also important to make sure you apply enough adhesive. I like a 3/16" or 1/4" notched trowel. Sounds like you're going to have a nice day down in VA. , so drop the hammer and get out into the garden!!
*Jeez,Why would you do a complete bathroom remodel and not replace worn out subfloor? I wouldn't spend the bucks on vinyl or tile, fixtures or paint and not spend the $300 for a new subfloor. I don't get it.
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Well Scooter, I did'nt think that the subfloor was
bad enough to need replacing. Although it is rough
on the surface, the surface is quite even. I assumed
that the function of the nice, smooth underlayment
was to mitigate the effects of the rough subfloor
surface. I tried to sink a drywall screw into a
scrap of nice, new plywood (3/4 inch) and it stops
just proud of the surface without countersinking,
just like my experience with the subfloor. I'm
leaning towards tar paper and ringshank nails at
this point; if you have any suggestions, I would
appreciate it.
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First of all don't use drywall screws. Use them with drywall. they are very brittle and shouldn't be in a floor. Also, as you have found, they don't grab as well. Use screws of appropriate length -- no threads should engage the surface that you're attaching.
The subfloor is in "rough shape"? What does that mean? Has it detiorated or was junk used in the first place? If you're talking water damage, just pull the stuff out, and then check the joists too. 1/2" is generally inadequate anyway unless the joists are maybe 12" apart. 5/8" or 3/4" underlayment grade should be about $20 a sheet -- cheap insurance. You don't want to lay all your finish work on a surface that might let you down -- then everything goes to heck because you didn't spend $100 and a few hours at the start.
*Paul,first of al, you should not be using screws in your luan. they make for a lot of patching before you lay your floor finish plus they also couse the wood to splinter up around the heads. I guess that with vct, you can get away with a little more than if you were using sheet vinyl or residnetial tiles. Secondly, if the screws are spining and not pullin themselves flush, then they will most certainly, without a doubt pop up over time. They may feel like they are holding but with time, a lot of foot traffic and the natural movement of things, they will come loose. Replace the subfloor and have a job done right. then use undelayment nails to secure your luan to the subfloor at one nail every 4 inches (right through the subfloor).Simply floored,Pete Draganic
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I am attempting to attach 1/4 inch plywood underlayment (tecply) to 1/2 inch plywood in a bathroom remodel. The
1/2 inch is about 40 yrs. old and is in
pretty rough shape. I have been advised
to nail or screw every 6 inches in the
field and 4 inches at the perimeter.
Does this mean fastening in some places
to the subfloor and joists and only to
the subfloor in others? I have tried
fastening a scrap of the underlayment
to the subfloor with 1 1/4 inch drywall
screws and the screws don't have enough
grab to countersink their heads into
the underlayment, although they are not
loose. They just spin in the plywood
without drawing tight. I was advised by
some to use a pneumatic stapler, but I
have my doubts as to the ability of the
staples to hold. I will be installing
commercial grade VCT. I think the plywood has seen a bit of water and may
have some delamination. I read a posting by a fellow named Lalonde who
recommends carpet glue and ring shank
nails. Will the ring shank nails stay
put and not pop? Or is there a screw
that will grip better in the plywood?
I tried a particle board screw (aggressive thread) and it did'nt perform any better than the drywall screw.
Any thoughts? - Thanks much -Paul S.