Floor laying: solid wood floors, floating floors and subfloors

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

Inden gulvlægningen starter, skal både bygning og materialer være i det rette klima. Massive trægulve og parket har typisk et fugtindhold på omkring 8 % (±2 %) fra fabrikken, og de skal akklimatiseres til det rum, de skal ligge i. Sker lægningen i et for fugtigt eller for tørt rum, kommer gulvet ud af balance, så snart klimaet normaliseres. Restfugten i et betonundergulv skal desuden være målt og bragt ned, før man lægger trægulv oven på — det behandles i sin egen artikel.

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.