Why does my new floating floor feel spongy and hollow?
A floating floor that sinks slightly underfoot or sounds hollow has one of four causes, and only one of them is a fault in the floor itself.
- Difficulty
- beginner
- Time
- 45 min
- Read
- 3 min
Short answer
Press and listen to map the area. A general softness across the room is usually underlay that is too thick or too soft. A localised sponginess is a hollow in the subfloor beneath. A hollow drumming sound with no movement is normal acoustics. A soft area that also creaks is a subfloor deck problem, not a covering problem.
A floating floor is a stiff raft on a compressible layer, so it is never going to feel like a bonded floor. But there is a clear difference between the slight give that is normal and a floor that sinks, drums or crackles — and the diagnosis is quick because the four causes feel different from one another.
Step by step
- Map the affected area precisely.Walk the floor slowly, marking with tape where the feel changes. Whether the problem is general or localised is the single most useful piece of information.
- Listen as well as feel.A hollow drum with no give is acoustics. A crackle is contact. A silent sink is compression. These are three different faults.
- Check what underlay was used against the specification.The flooring manufacturer states a maximum underlay thickness and often a minimum density. Fitting a thick soft underlay under a thin board is a common and understandable error, and it produces a floor that never feels solid.
- Take the beading off and look at the perimeter.Removing a run of scotia lets you see the underlay, the expansion gap and often a slice of the subfloor without lifting anything.
- Lift a small area over the worst spot.A floating floor comes up from the last row laid. Even lifting a couple of rows at a wall lets you get a straight edge onto the subfloor.
- Fix the layer that is actually at fault.The subfloor if it is hollow, the underlay if it is wrong, the deck if it is loose. Relaying the same covering over the same fault gets the same result.
If it doesn't work
Slight, even give across the whole room, no noise
Cause: Underlay that is thicker or softer than the flooring manufacturer specifies, or two underlays stacked — Fix: Check what was laid against what the manufacturer specifies. Stacking underlays, or using a thick acoustic underlay under a thin board, produces exactly this. It has to be lifted and the underlay changed.
One area sinks when you stand on it and springs back
Cause: A hollow in the subfloor under that area — a dip in the screed, a low board, a missing packer — Fix: Lift the floor over that area and check the subfloor with a straight edge. Fill the hollow with a levelling compound or pack it out, then relay.
Sharp crackling or clicking underfoot but no movement
Cause: The raft rocking on a high spot, or debris trapped under the underlay — Fix: Lift and check the subfloor for high points and grit. This is the same diagnosis as a creaking click floor and there is a separate guide on it.
Drumming hollow sound but the floor is firm
Cause: Normal — a floating floor over a void or an air gap is acoustically live — Fix: Not a fault. A denser underlay, an acoustic underlay or a rug reduces the resonance, but the floor is doing nothing wrong.
Soft area over a timber subfloor that also creaks
Cause: A deck problem below — a loose board, an unsupported chipboard joint or a failed fixing — Fix: The covering is fine. Lift it locally, fix the deck properly, and relay.
Softness that appeared months after laying, with a slight smell
Cause: Moisture below, compressing or degrading the underlay and possibly the subfloor — Fix: Lift immediately and test the subfloor for damp. Do not relay until the moisture source is resolved and the subfloor measured dry.