Floor laying: solid wood floors, floating floors and subfloors
From spreading and blocking to the freely movable floor — the floor layer's basic forms
Introduction
A wooden floor is alive. It absorbs and releases moisture with the seasons and expands and contracts across the grain. A floor layer who doesn't account for this gets cracks in winter and bumps in summer. Good flooring work therefore involves as much giving the floor room to move as laying it flat and even.
Subfloor types
The subfloor is what the visible floor rests on. It can be built in several ways depending on the building: as a straw floor on straw as a board subfloor or as a concrete leveling layer. The choice depends on the substrate requirements for impact sound and on how much building height is available.
- 01Joist floor — floorboards or panels are laid on joists (beams) that are propped up from the base
- 02Floating floor — the floor surface moves freely in relation to the substrate via an elastic intermediate layer
- 03Plate subfloor — plates form a flat, stable base for the final covering
- 04Levelling layer — a plastered or flowing layer that levels an uneven concrete deck
The joist floor and propping
With a flooring system, the straps are laid as long as possible and preferably without joints because each joint is a weak point. The straps are blocked up from the base so the floor comes level and the blockings distribute the load. If a joint is necessary, it must be supplemented with extra shims and the distance between the shims around the joint reduced by at least 10% so the joint does not become a weak spot that gives way.
Movement joints and adjustment
Because wood works across the grain, there must always be a movement joint along all walls and fixed objects. The joint is hidden under the skirting board, but it is not just cosmetic — without it the floor presses against the walls as it expands and bulges. In large floor areas and in transitions between rooms, expansion joints are also built in, which divide the area into sections that the floor can work within.
Climate and humidity before laying
Before floor laying starts, both building and materials must be in the right climate. Solid wood floors and parquet typically have a moisture content of around 8% (±2%) from the factory, and must be acclimatised to the room they are to be laid in. If laying occurs in a room that is too damp or too dry, the floor goes out of balance as soon as the climate normalises. The residual moisture in a concrete subfloor must also be measured and brought down before laying a wood floor on top — that is treated in its own article.
| Floor structure | Strength | Typical use |
|---|---|---|
| Joist floor on joists | Evens out uneven substrate allows space for installations. | Older floor separations, renovation |
| Floating floor | Good step noise insulation, quick laying | Apartments, laminate and laminate parquet |
| Plate subfloor | Plant on solid, stable ground | Under carpets vinyl and linoleum |
| Fully glued floor | Solid, no cavity sound | Solid wood floors on suitable substrate |
Floor laying is a craft within the craft. It requires understanding of wood movement, the condition of the substrate and the acoustic and moisture requirements of the individual building. A floor laid with respect for all three lies flat, quiet and crack-free for many years.