Average cost for leveling a cement subfloor, or any advice?

2 years ago

We are renovating a condo built around 1950, and are planning to replace old carpet with luxury vinyl plank flooring. When the carpet was removed, we discovered that the concrete subfloor had significant leftover mortar from a previous tile floor installation, as well as some chipped out areas. The attached photos aren't great but give some idea of the subfloor condition. There are at least some areas with almost 1/2'' between the low and high spots.

Understanding the the costs will vary depending on the actual condition of the floor, and the location, what would the average cost be for leveling the subfloor? It is approximately 400-450 sq ft. We are also interested in whether this could be done with something like LevelQuik. We have also gotten a recommendation to use Eco Cork Foam underlayment, but some quick research suggests the floors need to be relatively level before using the underlayment, and that it would not be appropriate with the LVP which already have an attached underlayment.

Any advice would be greatly appreciated!

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Comments (6)

SJ McCarthy
2 years ago
Ouch. In my neck of the woods (expensive Canadian city) I would expect $3-$4/sf. That would be for the labour (grinding) and for most of the leveling. My concern is the AGE of the concrete. Is any of this at or below grade (ground level)? If it is, you could be looking at more because the concrete might be difficult to get new stuff on top. Slabs (at or below grade) of that era were NEVER sealed underneath = moisture issues.

And vinyl really hates underpad. Eco-cork (did you know it is 90% + of foam and only 10% cork??...yah...talk about cashing in on the 'cork' fad without having to pay for it in the product) is not rated for LVP.

And any LVP with existing backing is NOT allowed more. That's the biggest issue with vinyl. It is not laminate. It does not behave like laminate. It is thinner than laminate and the click-edges are more delicate than laminate. Which is why a near-perfect subfloor is needed for vinyl.

If you were to 'guestimate' $5/sf for the subfloor prep, you *should be safe.
PRO
G & S Floor Service
2 years ago
It will cost anywhere from $3-$7 psf. Depending on the condition of the subfloor. It can cost more.

Your floors will be around the $5.00 mark. Needs grinding first. If, it is really bad, then you’re looking at the $7.00 or more.
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I would suggest 1/2" cork underlay = quick floor height raise (no nails, no glue) underneath the floating laminate to get you even with the kitchen. Remember: tile will raise the kitchen floor by 1/2" once it is set....Even if you remove the vinyl, prep and then lay tile you will be raising the height even more. Just remember that. I wonder if the kitchen floor was raised because of the height of the carpet. It is *possible the vinyl can be removed by removing the underlayment it is sitting on. It might just be 1/2" chip board. If it is chip board, tiles don't like to sit on top of that surface which means more work. A bit of effort and hopefully that underlay + vinyl floor will come up. A floor cutter will work at the base of the cabinets. Cabinets can stay in place. No problem there. Once that step is gone, you can make all the decisions without this elephant in the room. It is possible to get rid of this step. It is such a small amount of flooring I would hate for you to make a "whole home decision" based on 60sf of kitchen. That feels like putting the cart in front of the horse. Before you purchase anything - see if you can remove the step/underlay with the vinyl.
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The problem with a slope is it is rarely on the same PLANE. There are several floors that I know of that can handle a slight slope....but they cannot handle humps and bumps AS WELL as a slope. It is intensely rare to find a perfectly FLAT floor with a slope that is PERFECT. What happens? The click edges break with the stress. The little bumps and waves in a floor with a slope can and will stress the click system to the point of breaking. And it will happen over time. As it is walked on, the planks flex. As they flex, they cause stress fractures in the click system. Eventually the edges break and you get a floor that begins to gap. Once it starts, it is almost impossible to stop. While you wait for the vinyl edges to break, you will also get this lovely 'slappy' sound under your feet. The flex in a vinyl floor can be SO big it will visibly move every time you step on it. Again, this is more pronounced on a sloped floor that isn't flat. This is where laminate and vinyl are different. Laminate is very thick and very sturdy. Vinyl is thin and often quite easy to damage without proper training/preparation. In fact, the amount of swearing going on while a vinyl click together floor is being installed is IMPRESSIVE! And I grew up with 'angry Irish'. It takes a lot for me to call swearing "impressive". Vinyl planks are often very thin (4-5mm thick). That means the click egdes are VERY THIN (2mm deep...if you are lucky). That means there isn't much "grab". The tensile strength of the click system is very weak. A shift (when you step on it) up and down and a little side to side will rip the planks apart. Even if the edges remain intact (not broken), they simply do not have the strength to stay locked together. So imagine purchasing 1000sf for $4/sf = $4000. And imagine you then take 3 days to install it. Now imagine it fails within 6 months to 1 year. Will you feel the money you saved on the cost of subfloor prep ($2 - $4/sf) was worth it? Once you fix the basement subfloor (one time cost of $2-$4/sf depending on how bad it is) you can have ANY floor you want in there. You never have to fight with it again. I know that's not what you wanted to hear. Anytime there is a sloped floor (those basement drains are fun aren't they?), it is always best to remedy them before putting in flooring. The only floors that are OK with this type of floor = carpet and sheet vinyl/lino. Every other floor needs that basement slab to be fixed.
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ShadyWillowFarm
2 years ago
Yes, the floor needs to be leveled before doing lvp. The lvp will not stay clicked in if you do not have a level floor.
Bruce in Northern Virginia
2 years ago
LevelQuik works well if the perimeter of the room is consisent height, but remember that it all depends on gravity. You need a full perimeter border around the area you want to level, and the poured concrete will find the true level point in that entire area. You can't make the floor slope in any direction. It has about the consistency of cake batter, or even thinner.

LevelQuik is also quite expensive for a large area, so do your estimate ahead of time. For example, we added about 1" to level a fireplace hearth and IIRC it took 2+ 50 lb bags, at about $28 a bag. If you use RS (rapidset) you do not have very much time before it starts to set up, so you need a good sized crew to keep the process going for a larger floor.. However, it sets up quickly and is a truly level surface.

Bruce
L D
Original Author
2 years ago
Thank you all, this was very helpful!

Luckily the unit is on the second floor, so it is above grade. We had previously installed the LVP in a bathroom remodel, after chipping up all of the leftover mortar to get an even subfloor. In this case, the contractors doing the kitchen renovation installed the LVP without leveling the subfloor. We aren't living in the condo, so we did not notice until a week or two after the floors were installed when we realized you could feel how uneven it was. After several weeks of insistence that it was just movement associated with a floating floor installation, they had to remove several planks they cut too short, and we were able to confirm the subfloor had not been leveled.

They still tried to say it wasn't necessary to level the subfloor, but when pressed offered the eco-cork as a solution. It seemed like this was counter to BOTH the LVP and Eco-Cork manufacturers' specifications, but I wanted to confirm this wasn't sort of a standard, "off-label" solution.

Looks like we will be finding someone else to prep the subfloors!
SJ McCarthy
2 years ago
I hear ya'. Subfloor prep is long, dusty, tiring and requires multiple visits to the space. If you didn't pay for it (or even discuss it) then the installation company doesn't do it. What *should have happened is: they call you and tell you, "Uh oh. We've got a problem. This concrete needs work. I will come up with a plan and a quote for you in the next day or two."

That's when most homeowners get suspicious that their reno company is trying to jack up the price. And then the questions start to fly.

This is very common. If the quote didn't include subfloor prep, then you got what you paid for (tongue firmly in cheek). What bothers me is they have NO IDEA about vinyl. This tells me they think vinyl is identical to laminate. And THAT'S what upsets me the most!

You are right to move on to find someone who knows about flooring. The reason you are moving on is because these guys are clueless about A: Flooring and B: vinyl flooring.

It isn't the 'lack of subfloor prep" that bothers me. You didn't get a quote for it....so it wasn't done. That bit is 'fine'. The fact they tried to hide their total lack of knowledge about flooring and vinyl flooring especially is the MOST DISTURBING part about this.

Average cost for leveling a cement subfloor, or any advice?

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SJ McCarthy

G & S Floor Service

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Bruce in Northern Virginia

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Average cost for leveling a cement subfloor, or any advice?

Comments (6)

SJ McCarthy

G & S Floor Service

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ShadyWillowFarm

Bruce in Northern Virginia

L DOriginal Author

SJ McCarthy

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GET HELP

CONNECT WITH US

L D
Original Author