Almost every basement we look at in this valley has floor paint on it. Grey, red, or that particular institutional green that shows up in houses built before about 1975. Frequently more than one of them, layered.
All of it comes off. Not scuffed, not sanded, removed down to concrete.
Why it cannot stay
A coating bonds to what it is applied to. Apply it over old paint and your new floor is attached to that paint, and the paint is attached to a slab that was almost certainly never prepared before it went on.
So the strength of the whole system is the strength of a fifty year old bond that was weak to begin with. It will hold for a while. Then it lifts, and it lifts taking the old paint with it, in sheets.
There is no product that solves this. A bonding primer over failing paint bonds beautifully to failing paint.
How many layers we usually find
More than the owner expects, is the honest answer. Repainting a basement floor was a normal thing to do every decade or so, and each coat went over the last one.
We find out during grinding rather than before, because you cannot see layers from above. That is one reason a basement quote carries a wider range than a garage quote: the removal is the variable.
What removal involves
Diamond grinding, with more aggressive tooling than a bare slab needs and more passes. Older oil based paints are tougher than modern latex, and some of them clog tooling as they heat up.
It runs under dust extraction, so the mess stays in the machine. It is slow, and it is the reason a painted basement takes longer than an unpainted one of the same size.
Lead paint, and being honest about it
Floor paint in a house built before 1978 can contain lead. Grinding it produces dust, and that is a regulated activity with specific requirements around containment, worker protection and disposal.
If your house is that old and there is paint on the basement floor, say so when you call. It changes how the job is scoped, and any contractor who shrugs at that question is one to be careful with.
What it does to the price
It is a line item, not a hidden multiplier. Heavy multi layer removal across a whole basement can add hours, and hours are what this work costs.
We quote it after seeing the floor, and if we find substantially more than expected once grinding starts, we stop and talk to you rather than adding it to the invoice.
Can you just leave the paint and put something else down?
You can float LVP or lay carpet tile over painted concrete, yes. That is a real option and sometimes the right one.
What you should not do is seal over it, because you are then trapping vapor under a failing layer, which is the worst of both.
Related
- What we do on basement floors
- Why coatings peel, the general version of this problem
- Basement floor options if you would rather not grind
Reference
Existing coatings and contaminants must be removed to sound concrete before recoating. The preparation methods and the profiles they achieve are set out in Guideline 310.2R from the International Concrete Repair Institute.