What product to use to make concrete substrate flat?

[TheSJ]

Hello,

I would like some input on making the substrate flat prior to LVP installation on a DIY home project. The project is for a 6' x 7' bathroom. The substrate is concrete in a basement. The floor shows a maximum deviation of 0.14" when checked with a 6' straight edge in the main foot traffic area of the bathroom. In one corner of the bathroom (next to a foundation wall and where the toilet will be installed), the floors shows deviation of 0.42". The area with the 0.42" deviation is roughly and area of 12" x 12". So a relatively small area of the total room.

The manufacturer of the LVP states "All subfloors and substrates must be clean, flat (smooth) and dry prior to installation. All subfloors must be flat: High or low areas exceeding 3/16" per 10' or 1/8" per 6' must be corrected."

My question is: What product should I use to make concrete substrate flat?

Is a self leveling liquid product best practice in this application? Something like Sika Pro Select Self Leveler?

Is a patch compound that can be built up best practice in this application? Something like Henry 345?

Specific products (make and item name) is appreciated.

Thank you!

 

[havasu]

I wouldn't patch. I'd rather use self leveling compound. The flatter the floor, the better the LVP will turn out!

Mapei self leveler compound is my choice.

 

[Commercial Floor Rep]

The answer is probably going to depend on how far off the floor currently is.

If the floor has a significant high spot, you may need very little patch and instead you may need to grind an area, to remove the high spot.

If the floor is 1/2" out in 6', then a self-leveling product may work better than trying to float in patch.

But, if the floor is fairly flat and just needs some minor spots addressed, then a trowlable patch or feather patch would probably work best.

 

[Incognito]

.14" in 6' isn't going to be a problem

smooth out any holes/cracks/depressions with something like Ardex Feather Finish and a trowel--------you might just need a 6" putty knife with such a tiny space

there isn't any need to worry about level/flat where you're setting now according to those measurements you cite

I'm curious how you got a .14" reading.........digital level?

 

[havasu]

I was just considering with a 42 sq ft job, and a corner deviation of .41", seems it would be a "one and done" with a bag of SLC. Nice and flat, with no deviation.

 

[Incognito]

I was just considering with a 42 sq ft job, and a corner deviation of .41", seems it would be a "one and done" with a bag of SLC. Nice and flat, with no deviation.

I'm sure that would work. I just think it's overkill. One 10# bag of Feather Finish is going to fill that with plenty left over for future use. I really don't like trying to mix partial units of self-leveling and it wont last long in anything other than perfect storage. We only ever used the Ardex K15 and I think those were #40 sacks. I never loved wrestling with those.

 

[MSLI]

Wouldn’t it be nice if the big box stores or independent retailers would except back unused items like patch, and ! Rent out aged challenge installers to assist DIYers with knowledge and proper tools.

 

[Incognito]

Wouldn’t it be nice if the big box stores or independent retailers would except back unused items like patch, and ! Rent out aged challenge installers to assist DIYers with knowledge and proper tools.

Open bags of cement/grout/patch are a nightmare even for professionals to handle. I'd always try to put them and keep them in plastic pails with a lid between use. Can't even imagine the mess minimum wage retail store workers and customers would make with them.

 

[Csason]

You can always assemble some and walk on it or push down on it see if it telegraphs or is lumpy.

I am using the OP term “LVP” as a click floor.
LVT has to be zero everywhere or as close to it as possible

Also any of the major brands are fine, mapei or sika or if you’re wealthy buy Ardex big red bag of self leveler cap and seal that toilet flange pour it and go home leave it over night

 

[TheSJ]

.14" in 6' isn't going to be a problem

smooth out any holes/cracks/depressions with something like Ardex Feather Finish and a trowel--------you might just need a 6" putty knife with such a tiny space

there isn't any need to worry about level/flat where you're setting now according to those measurements you cite

I'm curious how you got a .14" reading.........digital level?

For the reading, I laid down a 6' level, shined light towards it to reveal the gap between the floor and level, slid a wood shim underneath the level until the shim made contact with the level, marked the contact area on the shim, pull the shim out, and used a digital caliper to measure the thickness of the shim where the mark was made.

 

[TheSJ]

Thanks everyone, I picked up some pre mixed/ready to use Henry 345 Patch and Level and will work it in with a hand trowel to get the floor uniformly flat.

 

[highup]

Let us know how the patch is to work with. I didn't know there was a ready to use product out there.

 

[kwfloors]

6x7 bath, with a cabinet and a toilet I don't think it would matter with what is showing.