Engineered Hardwood on slab

8 years ago

Quick question:

We are in the flooring phase of our new build. The hardwoods are almost done on the upper floors. This afternoon, they started installing the glue-down boards on the basement slab. The installers did not use self-leveling compound. When I asked about it, the installers and by foreman agreed that the slab was in good shape and they thought SLC was not necessary. They are willing to stop work and get me a price to level the floor before continuing. Should Self Leveling compound on a basement slab be standard practice or only if the floor looks out-of-level? They already think I'm nuts and don't want to throw away money, but I want to be sure this is done right. Any comments from the pros on this board? Thanks!

Featured Answer

PRO

Uptown Floors

8 years ago

I deal with a number of below grade engineered hardwood installations. Quite common. There are no drawbacks unless there are moisture issues already mentioned. Nowadays there are several products to assist in blocking moisture through the slab. This job is on the coast of Rhode Island.

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Comments (10)

User
8 years ago
last modified: 8 years ago
One. Wood of any variety does not belong below grade. Vinyl, porcelain, or carpet only.

Two. All slabs require prep for anything.
PRO
G & S Floor Service
8 years ago
Like Sophie mentioned, all slabs require prep, even new 30 day old slab. It should be tested for moisture, also. So, they know what type of moisture barrier to use. Which sounds like they are already passed that stage.
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Intoodeep
Original Author
8 years ago
They checked for moisture and prepped the slab. The only question is “are there any variances in the slab in the hardwood area?” I have asked that question and suggested they check with a laser level. Will know the status soon. Thanks for the advice.
PRO
G & S Floor Service
8 years ago
Uptown, why isn't the Pat's game on the television?
SJ McCarthy
8 years ago
Glue down wood (engineered or otherwise) below grade is ALWAYS tricky. Failure rates can be quite high even with all precautions taken. Basement installs and slab-on-grade in the gulf states are the reason why Humans created floating engineered flooring.

I'm extremely concerned about a glue down install in a basement - regardless of the moisture barrier below the slab. A GOOD builder will ALWAYS ASSUME that barrier HAS FAILED (regardless of the age). That means they *should be using the MOST EXPENSIVE moisture barrier adhesive on the market ($3/sf).

And Sophie is correct. The slab is NOT ready. The pour would have ASSUMED the FLOORING GUYS would do the work. If the flooring guys didn't do the work and the cement POUR didn't do the work, then the work wasn't done.

As for paying for subfloor prep....this is a new build. Why is this NOT already accounted for?????
Intoodeep
Original Author
8 years ago
@SJ "Why is this NOT already accounted for?????" The very question that I asked. It is cost plus, so I have to pay for it anyway.
SJ McCarthy
8 years ago
Ahhhhh....cost PLUS is in the fine print. It's how builders make a bid "look good" only to have the ability to add on as "costs" build up. See how that works?

So...you need the slab to be relatively flat and level. A wavy/slanted slab will have to be dealt with. The *average requirement (the number we see MOST often for most floors) is 3mm over 3meters (1/8" over 10ft). The easiest way to "see" this is to use a 10ft level and "sweep" it across the surface of the slab. When it starts to teeter-totter you take the measurements. In 10 minutes you will have an EXCELLENT idea of how much work is needed. The laser measurements will be used for the full assessment.

And PLEASE check to see that the glue they are using has a HIGH moisture barrier quality to it. Somewhere in the write up (on the company website) it should say "unlimited" moisture protection. Something like that. If it doesn't, you have a high chance of problems in the future. It could be tomorrow. It could be 20+ years from now. But the risk is there.
Intoodeep thanked SJ McCarthy
Intoodeep
Original Author
8 years ago
@SJ - Thanks for the tip. I will definitely check. And yes, cost plus is a nightmare, but at least I have more control than if it was a fixed price. Then they would just do whatever they want!
SJ McCarthy
8 years ago
Glad to help Intoodeep. I hope this works for you. If the engineered hardwood is allowed to be FLOATED, you can REDUCE the cost of install because you REMOVE the need for the expensive glue. The concrete prep still needs to be done (flat is flat no matter your installation method) but you get AWAY from the need for a STUPID-EXPENSIVE glue.

Underneath a floating floor you can use the industry standard 6mil polypropylene sheeting taped at the seams (works out to be $0.12/sf....compare that to $3/sf for the glue). You can then spend a bit on a nice under lay like 1/4" cork ($0.90/sf) and STILL save money.

And the installation/labor costs are MUCH lower with a floating floor than a glue down.

So....you can eat your cake and have it too....AND save money with a floating floor install (which is MUCH more appropriate for a basement). Have a think about it.