Summary: Measurements and advice when laying floors – Expansion gaps, floorboard sizes, dimensions for floating floors, dimensions when using tongue-and-groove boards and recommended board lengths.
When laying solid wood floors it is important to leave a gap between the board and the walls to allow for expansion. In general, wood-engineered floors expand and shrink less than solid wood floors.
Solid oak floors require a 4mm (1/8in) expansion gap for every meter width of the room with a minimum 10mm (3/8in) gap. For example, a 4 meter wide room would require a 16mm (5/8in) expansion gap, a 3 meter wide room would require a 12mm (1/2in) expansion gap.
Pine floors require a 4-5mm (1/8in – 3/16in) expansion gap for every meter width of the room with a minimum 10mm (3/8in) gap.
Beach floors require a 7mm (1/4in) expansion gap for every meter width of the room with a minimum 10mm (3/8in) gap.
Wood-engineered floors act differently to solid wood floors and only require a 10mm (3/8in) expansion gap.
When using solid wood boards, the width should never be wider than 10 times the thickness of the board. Boards that are out of proportion are inclined to buckle and cup. For example, a 20mm (13/16in) thick board should be no wider than 200mm (8in).
The minimum width of the solid wood boards when used floating should be 100m (4in). It is recommended that the room should be no wider than 5-6 meters.
Tongue-and-groove floorboards need to be at least 18mm (3/4in) thick when installing directly onto joists. Boards are more durable and steady when the tongue-and-grove on the board depth is central. Boards with tongue and grove near the bottom are more liable to cup.
Cut–offs and board lengths
Quality wood floors can contain up to 15% of boards that are shorter than 400mm (16in). If the product you plan to install has random board lengths, and over 20 – 25% are 400mm (16in) or less, (or 25% or more are of the shortest length), your floor can become unstable due to the many joints which will work as hinges.
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