Solid Hardwood, Engineered and Laminate Flooring - Hardwood over Engineered over concrete

DIY

My wife and I are in the process of a remodel and we need to verify how we should go about the prep steps involved to lay nail down hardwood floors.

In our particular installation we have existing glued down 3/8 eng wood flooring over concrete in an adjacent existing area.

To match the old area to the remodel area we thought we could save time/money by laying 3/8 plywood over the eng wood flooring and lay down 3/4 plywood in the new area.

The other way is to rip out all the 3/8 glue down, repair/level concrete. However, when I try to remove the eng. wood flooring it is also pulling up small quarter to silver dollar size patches of concrete.

Any concerns/thoughts would be greatly appreciated!!

There is more to installing hardwood over concrete, than what your expecting to do, and go about it.

The engineered must be completely removed. Moisture barriers are a must with solid over concrete.

CDW,

Thank you for the reply.

I understand there is more prep than I listed I.E. Vapor barrier,plastic or asphalt paper & Cold cut-back mastic, then
spending the rest of the week shooting nails into your slab.

I needed a professional to confirm that the original glue/vapor barrier would not be enough for the solid. Thank you!!

How about a different route like laying 3/8 plywood over the original glue down and then go over that with a glue down or staple eng.

Then putting 3/4 ply in 16"x8" planks over the new addition in cold cut-back mastic. Shooting that many nails cant be good for anything.

Appreciate your time and input!!

You are going to have to remove the existing glue-down.
Install 6 mil poly.And you can also float your subfloor if you dont have an Arrowsmith or other concrete fastener. This can be done using 2 layers of 3/8'' CDX installed perpindicular to one another and srewing them together.

Thanks for the input floorguy.

I have a hilti brand gun, that'ss not the problem. I'm hesitant
about two things: qty of hilti nails into the slab (450) and when you shoot through the plastic is that really a barrier then?

Any thoughts?

How about the float system using 3/8 ply, that sounds interesting. It would just lay over the plastic then? Do you glue and screw the two together, ie liquid nails or such. Excuse my question: is that stable enough to nail to then?

What's your take on the following:

Going over the original with glue.

Going over the original with staple down by putting 3/8 over the glue down.

Appreciate your time & input !!

What size flooring are you going to replace it all with, full 3/4" or another laminate? 3/8" plywood won't be sufficient, nor will your plan of leaving the original flooring. Both of the other professional posters have advised against going over the original with glue, going over the original with staple down, so you are left with one more corroboration....remove the old flooring and apply a good moisture barrier. I would probably not go with any staple down flooring on a concrete floor. The engineered flooring out, now, featuring clicklock technology is far superior to the old stuff. Some even have the padding attached. It is highly diy friendly.

Both of the other professional posters have advised against going over the original with glue, going over the original with staple down,


Chandler, thanks for the reply!

I guess I' read the other responses differently. No one has said that I can not nor should I go over the old flooring with glue down or staple. They just state it has to be removed to start over.

I realize I can start all the way over by ripping out the old floor approx 1000 sqft. Which when taking out takes up small chunks of concrete. Repair concrete, put down glue, or put down nail down with 50 sheets of ply with 450 hilti nails.

I'm looking at all possible avenues "trying" to utilize the original 1000 sqft already down either for glue down or part of a subfloor that I would have to add to. I dont mind about the the build up and transition into other rooms.

Appreciate the feedback!

If you rent a buffer and use it to rough up and clean the finish on the existing floor, you may get away with gluing down a new 3/8 inch engineered floor over it in a perpendicular direction. then you could either use 3/8 inch plywood to raise adjoining rooms or go right over the concrete and transition between them.
The problem with adding another layer of plywood over the existing is that you need a moisture barrier under the plywood, and that barrier will trap moisture in the existing floor that will be under the plastic, and cause it to rot. When you nail through plastic, the nails heat it up and it seals around the nails, at least partially, so the vapor barrier is effective and should be used under the solid wood's subfloor.

Thank you for the input!

I did think about the sanding the finish off the original eng and then putting down 3/8 ply down in cold cut mastic so both areas would be the same depth.

On the route with adding more ply for a deeper subfloor. Would there really be that much moisture trapped under the plastic to rot wood? I know you can't speak to my region/house, but in general. I know there is 6mil or heavier under my slab already.

Appreciate the feedback!!

You can't assume that the vapor barrier under the floor is even present at all. It can be full of holes, or could have completely biodegraded by now. If existing vapor barriers under slabs actually did anything, then where does the water in the concrete come from? If you trap moisture in a floor that is glued to concrete, 99% chance the wood will rot, but maybe it takes a year or two, unless you live in the desert, and moisture is not an issue to you then.

Floor you,

Appreciate the response!


The vapor barrier under the slab is in good shape. Had to rip up 2x10 section of slab in my kitchen to run new water, electrical & dwv for kitchen remodel.

Understand what you are saying about the moisture being trapped and present.