Issues with previous underlayment under floor

6 years ago

I am getting ready the floor for priming and self leveling, but unfortunately there are areas where there is too much underlayment of mortar or thinset from the previous floor that was taken out. I believe they also used self leveler to raise it. I removed the parts that made a hollow sound when I tapped a hammer on it - but is the floor going to be too high? Should I take everything out for being so high?! That could take years off my life.

Featured Answer

PRO

G & S Floor Service

6 years ago

You will need to remove all loose underlayment/cement. You will need to grind off the residue from the previous floor. It looks like contact cement from VCT. That's a bond breaker. Then you can move ahead with priming and self-leveling. If, that is not possible, do a small test pour, before you pour the entire floor. Make sure you have good bonding, otherwise, stuff will crumble.

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Comments (8)

SJ McCarthy
6 years ago
The idea is: If it is coming out EASILY then take it out. If it is a HORROR show for it to come up, then leave it be.

You will be left with a hot mess but you can be confident that what is left is firmly affixed (which is requirement #1). You then rough up what you have left and them make a plan for the large hollows left over.

There is no way to tell if a floor will be 'too high'. It is a combination of things that make a floor transition undesirable. The OTHER floor that is being left in place becomes the benchmark. The floor that is going IN will tell you what you have to do to REACH the benchmark.

Without knowing what is going in nor what it's going up to, we can't tell you if it is 'too high' or not.

As an aside, you have just discovered WHY subfloor prep can run $4-$5/sf. I admire your efforts. Let us know a few more things (photos work) and we can help from there.
Davied Davies
Original Author
6 years ago
last modified: 6 years ago
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Davied Davies
Original Author
6 years ago
kudzu9
6 years ago
Davied-

What are you intending to put down as a floor? That could bear on the right approach to this....
User
6 years ago
Anything lose must be removed. So start there. How out of level the floor was, and the impact of the removal dictate the next steps. What does your laser say?
Davied Davies
Original Author
6 years ago
last modified: 6 years ago
@kudzu9 7 inch wide engineered planks that are 71" long. Large individual planks that snap together and will be glued down.
Davied Davies
Original Author
6 years ago
last modified: 6 years ago
@User it tells me it was level with all the gunk on the concrete slab. This was after I used a huge angle grinder and burnt through 2 diamond cup hole disks ($90 each). My approach is to take off all the loose spots, fill in the big holes with cementall, lay a primer, then SELF LEVELING TIME with a small skim coat. I don't need it to go higher, but there are dips that is why the previous self leveler was there.