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Vinyl Or LVT Floor Bubbling
Blisters, ridges or soft raised areas have appeared in sheet vinyl or luxury vinyl tiles.
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What's happening?
Glued-down vinyl and LVT depend on a bond to a flat, dry, clean subfloor. A bubble means that bond has let go in that spot and something is filling the space — usually moisture vapour rising out of the base. The Contract Flooring Association's standard requirement is that a solid cementitious base is dry enough to show a hygrometer reading of no more than 75% relative humidity before a floor finish goes down, tested to the relevant British Standard code of practice. Concrete and screed laid without a damp-proof membrane, or laid recently and covered too soon, keep pushing vapour upwards for months. The other common causes are adhesive that was allowed to skin over before the vinyl went on, and a subfloor whose old adhesive residue or dust stopped the new bond forming.
What usually causes it?
- Subfloor moisture above the 75% relative humidity limit when the floor was laid
- A solid ground floor with no effective damp-proof membrane below the slab
- Adhesive left past its open time, so it had skinned before the vinyl was laid into it
- Dust, laitance or old adhesive residue on the subfloor preventing a bond
- The wrong adhesive for the product or for an underfloor heated floor
- Direct sunlight through patio doors heating and expanding the vinyl in one strip
- Water tracking under the floor from a leak, an overflowing appliance or a failed perimeter seal
Is it dangerous?
No, but a bubble in a doorway or a kitchen walkway is a trip point, and once the vinyl has lifted it creases and the crease becomes a permanent mark. Water trapped under a floor also stays there, so a bubble that follows a leak is worth opening rather than ignoring.
Can I fix it myself?
Very little, safely. You can look for the cause: check whether the bubble sits near an appliance, a doorway that gets rain, or an outside wall, and whether it grows after wet weather. A small blister in LVT can sometimes be released and re-bonded with the right adhesive, but if moisture is the cause the same bubble returns a few weeks later. Do not cut into sheet vinyl to release air — the cut will never close cleanly.
When should you call a flooring fitter?
Call a flooring fitter when the bubbling is spreading, when it has appeared across a ground floor, when a leak or an appliance overflow preceded it, or when you need to know whether the subfloor is dry enough to lay anything at all. A fitter will test the subfloor properly rather than guess, which decides whether the floor can be re-bonded or the base needs a surface damp-proof membrane first.
What will the flooring fitter actually do?
- Test the subfloor with a hygrometer to establish whether it meets the 75% relative humidity limit
- Lift the affected area and inspect the adhesive bed, the subfloor surface and any residues
- Dry, prime and smooth the subfloor, applying a surface damp-proof membrane where moisture is the cause
- Re-lay with the adhesive specified for that product, subfloor and heating arrangement
- Roll the floor and dress the perimeter and seams so water cannot track underneath again
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