If the floor gives underfoot, you are feeling the base under the liner, not the liner itself. Floor failure is invisible from the surface and is the repair most often skipped during a liner replacement, because it is discovered at the worst moment in the job.
What you are feeling
Inground vinyl pools sit on a vermiculite or concrete base formed over the pool floor. When that base hollows, delaminates or erodes, the liner loses support. You feel it as a spongy area, and over time the liner stretches into the void, wrinkles, or punctures where the base has broken away.
What causes it
Water is almost always involved: a slow leak that washes out the base, groundwater movement, or a floor that was never fully compacted or formed. In clay soil the movement is seasonal, and small voids open and close with moisture.
Cost of putting it right
| Scope | Published cost |
|---|---|
| Floor patching / vermiculite repair | $150 - $3,000 depending on damage |
| Full floor rebuild | $1,200 - $3,000 |
| Spot repairs generally | $150 - $600 |
The range is wide because the job is priced by area and by how much of the base has gone. Ask for the repair by area, and for photographs, because this is work nobody can see afterwards.
Why it cannot wait for the next liner
Fitting a new liner over a hollow floor is how a liner fails early: the vinyl bridges the void, stretches when someone stands there, and either wrinkles or tears. Any liner warranty discussion afterwards runs into the fact that the base was known to be defective.
Frequently asked questions
Why is my pool floor soft in one spot?
The vermiculite or concrete base under the liner has hollowed or eroded. It is a base repair, not a liner repair, and it needs the pool drained.
How much does vermiculite pool floor repair cost?
Published figures are $150 to $3,000 for patching or vermiculite repair depending on the extent, and $1,200 to $3,000 for a full floor rebuild.
Can a new liner hide a bad floor?
It can for a season. The liner bridges the void, stretches and then wrinkles or tears, which is why the floor should be assessed while the pool is empty.
