Preventing concrete moisture from damaging laminate flooring with underlayment

[vpfloor]

Advice appreciated:

We're planning to install laminate flooring with an underlayment that is an (acoustic + moisture barrier) type. The flooring salesperson says it *should* work but for added protection I could put an epoxy coating first. Would an additional plastic sheet also provide similar protection? Any recommendations for epoxy that is low VOC and economical? This is for a residential project of about 750 sq ft.

Thank you!

 

[C.J.]

‘Should’ work. Lol.

Have you done any moisture testing? Is the salesperson going to do any moisture testing? Why would a salesperson jump straight to an epoxy moisture control system without even knowing what your slab is doing right now. What’s the CSP of your slab? You gonna shot blast your slab first to create a profile the epoxy can bond to? Are they just trying to be safe because the laminate is junk or the installers suck? Maybe make an additional sale by just selling you some crap you can roll on? Just questions that I have cus many salespeople I know don’t know much about concrete and moisture beyond the fact that concrete gives off residual moisture.

What kind of flooring is currently down now? Carpet? Bare concrete? Is this a basement? Any history of flooding?

Anyway, I would say most jobs don’t get any kind of moisture testing at all. Sad but that’s just how it is a lot of places. I guarantee you the instructions for your laminate floor have specific limitations on the amount of moisture in the substrate it is able to be installed over, both wood and concrete. Hopefully the installer has a moisture meter to check the slab at the time of installation. Is this DIY? Do you have a moisture meter or will you have someone else do moisture testing? Most jobs just get a 6 mil vapor barrier rolled out then whatever installed on top. Many LVP jobs don’t even get that anymore because there are some people believe the floor itself is ‘waterproof’ so therefore you don’t need a vapor barrier. The combo underlayments work but they have to be installed properly. Seams taped together or whatever else the instructions call for.

What products are you specifically looking at having installed? Have you checked your floor for flatness? Are you prepared to pay for subfloor prep if it doesn’t meet flatness specs as is called for by your choice of flooring. You got any pics? Man, I got questions.

 

[rugaddict]

I think putting laminate in a basement is destined to fail—— lvp is much less sensitive to moisture

 

[vpfloor]

‘Should’ work. Lol.

Have you done any moisture testing? Is the salesperson going to do any moisture testing? Why would a salesperson jump straight to an epoxy moisture control system without even knowing what your slab is doing right now. What’s the CSP of your slab? You gonna shot blast your slab first to create a profile the epoxy can bond to? Are they just trying to be safe because the laminate is junk or the installers suck? Maybe make an additional sale by just selling you some crap you can roll on? Just questions that I have cus many salespeople I know don’t know much about concrete and moisture beyond the fact that concrete gives off residual moisture.

What kind of flooring is currently down now? Carpet? Bare concrete? Is this a basement? Any history of flooding?

Anyway, I would say most jobs don’t get any kind of moisture testing at all. Sad but that’s just how it is a lot of places. I guarantee you the instructions for your laminate floor have specific limitations on the amount of moisture in the substrate it is able to be installed over, both wood and concrete. Hopefully the installer has a moisture meter to check the slab at the time of installation. Is this DIY? Do you have a moisture meter or will you have someone else do moisture testing? Most jobs just get a 6 mil vapor barrier rolled out then whatever installed on top. Many LVP jobs don’t even get that anymore because there are some people believe the floor itself is ‘waterproof’ so therefore you don’t need a vapor barrier. The combo underlayments work but they have to be installed properly. Seams taped together or whatever else the instructions call for.

What products are you specifically looking at having installed? Have you checked your floor for flatness? Are you prepared to pay for subfloor prep if it doesn’t meet flatness specs as is called for by your choice of flooring. You got any pics? Man, I got questions.

Ah, you hit so many things on the nail, C.J. Many thanks for the detailed response and questions.

- This is the first floor of a home on a concrete slab foundation.
- We had laminate installed by the previous owners and I don't know for how long but we've been in the house for 8 years now and it was fine except looking dated, so I decided to change the flooring.
- We had hardwood flooring put down by a contractor (LLFlooring hardwood floors with a Shaw glue (a "no testing required" glue that had a built in moisture barrier). Disaster after two months when the flooring started cupping and buckling - big mistake.
- We now want to install fresh flooring and rather than hardwood, and we want to go with laminate with a proper moisture barrier put in.
- Flooring is Eternity Natural Oak.
- Underlayment is Eco-Ultimate.
- We haven't done a moisture test (yet!). My assumption is that there IS a moisture issue given what happened to the hardwood flooring.

You say that combo underlayments work but they have to be installed properly with seams taped together etc. Did you mean that for LVP or also laminate? Thanks

 

[C.J.]

Your underlayment you linked to states it has moisture limitations itself. One of the options if you exceed the allowable moisture is to use a polyethylene sheet, a 6 mil vapor barrier. It’s cheap insurance. Since you had laminate before I would say you will be just fine using it again. I would recommend using a 6 mil vapor barrier in addition to the combo underlayment. Like I said, it’s cheap insurance and so far you’ve had one success story and one failure. Don’t make it a second failure over something as trivial as $100. Maybe $200 if you’re paying someone else to do the job.

Many an LVP has the pad attached these days so a combo underlayment doesn’t really apply in many LVP situations, even though there are underlayments that people will try to sell you. A 6 mil vapor barrier is always a good idea regardless of what kind of floating floor you are installing. Laminate is moisture sensitive. The slow absorption of moisture will make your floor expand and eventually buckle. The vapor barrier is your protection against moisture. LVP is ‘waterproof’ but what travels in the moisture will break down the LVP itself given enough time or moisture. Again, a vapor barrier is your friend.

So your LL floor failed. Who woulda guessed. Again, I have questions. Was the adhesive properly troweled out. Was the wood properly acclimated? In theory your floor shoulda been fine but there are many variables as to why it didn’t. Attention to detail is key. Outta sight, outta mind it on a lot of peoples minds. The wood floor itself is what they focused on making look good but the unseen details caused it to fail. Same thing with a combo underlayment. Many installers don’t care what it looks like because it will be covered up and you’ll never know if it was half assed until it’s too late. With that in mind, rather than say laminate is a terrible idea in a basement, I would say your installer(s) will make the biggest difference as to whether your laminate floor survives. Next is how you maintain and care for your floor. Are you one of them steam mop nut jobs? That will blow your floor up just as quick as wet mopping it will.

 

[vpfloor]

Thank you so much CJ for the detailed reply and advice.