Why can I see every bump and joint through my vinyl floor?
Telegraphing is the subfloor showing through a thin covering, and it does not settle out — it deepens. What causes each pattern, and why the fix is always underneath.
- Difficulty
- intermediate
- Time
- 2 hr
- Read
- 3 min
Short answer
A thin flexible covering has no stiffness of its own, so it copies the plane it is laid on rather than bridging it. Ridges along straight lines are board or sheet joints. Round pimples are fastener heads. Random lumps are debris or adhesive left on the subfloor. All of them are cured by preparing the subfloor, not by replacing the vinyl.
People assume a covering will hide what is underneath it. Thicker, stiffer coverings do bridge a little — which is why a poor subfloor makes laminate rock and creak rather than showing bumps. Sheet vinyl and glued LVT are thin and flexible and bridge nothing at all, which is why the same bad subfloor produces a completely different symptom.
Step by step
- Look at the pattern of the marks in low, raking light.Get down to floor level with a light source low and to one side. The pattern tells you the cause: straight lines are joints, dots are fasteners, random is debris.
- Measure the spacing.Ridges at board width are floorboard joints. Ridges at sheet width are deck sheet joints. Dots at regular centres are a fixing pattern. This alone usually settles the diagnosis.
- Accept that it will not improve.A vinyl or LVT floor relaxes onto the shape beneath it over months, so the marks deepen rather than fade. Waiting is not a strategy.
- Plan the correction as a subfloor job.Whether that is punching fasteners, planing high edges, scraping debris, or overlaying the whole floor, the work is under the covering. Budget for lifting and relaying or replacing the covering as part of it.
- Overlay properly if that is the answer.Plywood or hardboard, screwed or nailed at the close centres the manufacturer specifies, joints staggered off the joints below, every head countersunk, and the whole surface vacuumed before anything is laid.
- Re-check flatness against the covering's own tolerance.With a long straight edge, in several directions. The number to work to is the one in the flooring manufacturer's instructions, not a general rule.
- Consider a thicker covering if the subfloor cannot be improved.Where lifting and overlaying is genuinely impractical, a click LVT with a rigid core, or a laminate, bridges more than sheet vinyl does. It is a compromise rather than a fix.
If it doesn't work
Straight parallel ridges at regular spacing
Cause: The joints between floorboards or between sheets of the deck below — Fix: The deck needs an overlay. Plywood or hardboard screwed down at close centres, with its joints staggered off the joints below and every fastener countersunk.
Small round pimples in a regular grid
Cause: Screw or nail heads standing proud of the deck — Fix: Punch or countersink every head below the surface. On a large floor this is the reason the overlay exists — it covers them permanently.
Random lumps in no pattern
Cause: Debris under the covering — plaster splashes, dried adhesive, grit — Fix: Lift, scrape the subfloor completely clean, vacuum twice, and relay. Grit is the reason professional fitters vacuum obsessively before a glue-down.
A long ridge along one line that was not there when laid
Cause: A cupped board edge that has risen since, or a screed crack that has lipped — Fix: Plane or sand the high edge on timber. On screed, grind the lip and fill, or apply a levelling compound over the area.
The whole floor looks slightly rippled in low light
Cause: General unevenness in the subfloor within tolerance for laminate but not for vinyl — Fix: This is a specification mismatch. The flooring manufacturer publishes a flatness tolerance and vinyl's is tighter. A levelling compound or an overlay is the answer.
Marks appearing only after underfloor heating was commissioned
Cause: Thermal movement in the subfloor opening joints and lifting edges — Fix: Take the commissioning sequence seriously — the heating should be run up and back down before the floor is laid, and the covering must be rated for UFH.