Glue or Nail down Hardwood floors

8 years ago

last modified: 8 years ago

I was under the assumption that our solid hardwood floors (3/4 inch x 5 inch white oak) were going to be nailed down on to the subfloor (plywood).

I told my GC that I wanted acoustic underlayment to dampen the sound, and he suggested IsoStep underlayment. However, it seems this will have to be glued down, and the hardwood will also need to be glued down on top of this.

Penetrating the underlayment defeats the sound barrier qualities. Is this going to be an issue if our kitchen ever floods and we need to replace the hardwood floor in it?

Also, is this preferred to say a cork underlay? If cork was nailed down, would it also lose it's sound absorbing qualities?

Thanks!

Featured Answer

PRO

Cancork Floor Inc.

8 years ago

And just to be helpful (probably not...but here we go), a 5" wide hardwood needs "glue assist" with a nail in place install. So there must be some gluing going on.

The extra cost of the sound reducing membrane isn't what is driving the cost up. It is the two layers of glue (yes the acoustic underlay must be glued and then the hardwood glued over top = double stick) and the extra labor to do everything "twice". Twice the labour, twice the glue = twice the budget.

A glue down hardwood is the most expensive form of hardwood install we have. Nailing is the cheapest. A floating method is between the two. A glue assist for a wide plank (ahem...5" ranks as wide plank = needs glue assist) is more expensive than a float...but not as expensive as a full spread glue down install. Check to ensure the quote for the nail down includes the glue assist. If it doesn't, then they could be missing a step.

The 1/4" cork underlay (from iCork Floor) = $0.66/sf. Some shipping costs (maybe $0.45/sf) brings it to about $1.10/sf for the cork. The other $5/sf is the glue (assume $1/sf per layer = $2/sf) and the extra labor to do all this gluing. The material only adds $3/sf. The labor is the other $3/sf. $3+$3 = $6/sf for this install.

If you MUST HAVE acoustic insulation + solid hardwood, then you must have the extra $6/sf. There is a possible solution: floating hardwood.

Yep. Float the hardwood (very few solid hardwoods are allowed to float...so you need to look at engineered for this) and you FLOAT the cork underlay. No glue = reduce the material costs by $2/sf. Since floating a hardwood is just SLIGHTLY cheaper than a "nail + glue assist" install, the cost of labor for the floor itself won't change.

Switch to an engineered hardwood that can float and then add the 6mm cork underlay. It will add $1 - $2/sf to your current quote. My calculations indicate you have 2500sf of flooring. The cork underlay will only add $2500 to your material costs. Compare that to $15K for the double stick total.

The solution = floating engineered hardwood. You can have your cake and eat it to.

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Comments (7)

PRO
G & S Floor Service
8 years ago
You can check with mfg to see if they allow a nail and glue assist over their product. Glue the underlayment, then glue (full mastic, not beads) and nail the solid flooring. Also, I would compare the cost to 1/4" cork. The cork will probably cost less, compared to the rubber type underlayment.

Cork would need to be glued down. Otherwise, it will break during installation.
Nirav Desai thanked G & S Floor Service
PRO
National Hardwood Flooring & Supplies
8 years ago
You are correct if you penetrate the barrier it defeats the purpose. yes cork also. Alternative would be using a 3 in 1 adhesive, adhesion, moisture barrier and sound proofing. check out Sika, Mapei, and Bostiks for products.
Nirav Desai thanked National Hardwood Flooring & Supplies
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PRO
G & S Floor Service
8 years ago
How serious are you about sound proofing: $2, $6, $8 or $10 per sq. feet? Keep in mind this does not include sub-floor prep, repair leveling or flooring installation. Proper sound proofing requires a flat floor to avoid hollow spots. Most clients only want a step up from the paper and not the extreme.
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Nirav Desai
Original Author
8 years ago
Thanks for your responses!

So the estimate for acoustic underlay came back at $6/sqft installed, plus the cost of installing the hardwood!

Since my budget doesn't have an extra $15k, what can I put down that's just a step up from regular tar paper?
PRO
G & S Floor Service
8 years ago
You can use any of the noise reducing underlayment for solid hardwood from your local home centers. That's a step up from paper.
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Nirav Desai
Original Author
8 years ago
Thanks for all the excellent explanations!