Floor build-ups: dry and wet

The difference: mass

A – dry floating floor, B – floor on steel decking. 1 floor finish · 2 damping layer · 3 floor joists · 4 thin concrete layer · 5 dovetail sheet, separated with rubber strips

The main question in choosing a floor build-up is how much mass goes onto the structure. Mass improves airborne and impact sound insulation and the vibration behaviour at the same time.

The cheaper: a dry floating floor

A damping layer separates the floor from the structure. A dry technology, fast, no curing time, and it puts little load on the structure.

Its limit: there is no real mass in it — and without mass there is always a limit to the airborne and impact sound reduction achievable.

A good choice where the requirement is moderate: within a house, between spaces used by one owner.

The better: a floor on Lewis dovetail decking

For higher demands — an apartment-building floor, for instance — we design a floor on Lewis dovetail steel decking.

The sheet counts as the bottom reinforcement, so a floor can be built at a thin overall depth that carries load and insulates well — with roughly 30 mm of concrete.

The concrete is separated from the steel sections with rubber strips, a cheap solution because it is not needed over the full area.

This build-up gives, at once:

• mass for the sound insulation,
• stiffness and mass against vibration, Floor vibration,
• a shallow structural depth,
• and a solid surface to receive a rigid finish.

What to watch in both cases

The perimeter

Floating only works if the floor does not touch the structure rigidly at the walls either.

Penetrations

A service pipe passing through the floor forms a sound bridge.

The rigidity of the finish

A rigid finish — ceramic tiling, say — may require a stricter deflection limit. Deflection limits.

The structural load

A wet build-up adds load, which has to be allowed for when sizing the joists.

How to choose

Use decides: who lives on either side of the floor. Within a single dwelling the dry solution is enough; between two separate dwellings the massive solution is warranted.

The point

The floor build-up is not a question of finish but an acoustic and vibration decision. Mass brings the most — and it has to be designed into the build-up.