Solid Wood Flooring Calculator — Boards, Fixing & Acclimatisation

Acclimatisation is not really a fixed number of days — BS 8201:2011 defines it as the flooring reaching equilibrium moisture content (EMC) with the room it will be laid in. As a typical guide that takes 7–14 days (e.g. ~14 for oak or walnut, ~7 for pine), but the only reliable test is a moisture meter: the boards should sit within roughly 2% of the room’s in-service moisture content (around 8% ±2%) before fitting. Open the packs and stack with spacers so air can circulate, and keep the room at normal lived-in temperature and humidity throughout.

Yes, using a flexible (elastic) wood-flooring adhesive. Consumption depends on the trowel notch and board thickness — typically about 0.8–1.3 kg/m² for solid boards (for example SikaBond MS Wood Floor is a minimum of 0.6 kg/m², SikaBond-5500 S 0.95–1.25 kg/m²), so always follow the rate and trowel stated on your adhesive datasheet. The concrete must be dry — for solid timber that means a hygrometer (insulated-hood) reading of ≤65% RH per BS 8201:2011 Annex A, the stricter limit wood needs because it is so moisture-sensitive (the ≤75% RH figure is for other, less sensitive floorcoverings). It must also be flat (±3mm over 3m) and have a working DPM. Alternatively, fix to plywood battens with a DPM underneath.

Secret nailing involves driving a fixing at 45° through the tongue of each board into the joist or subfloor below; the groove of the next board hides the fixing head. The rule is one fixing per board into every joist or batten — joists are normally at ~350–400mm centres, so for boards up to about 160mm wide one fixing per joist is enough. (Boards wider than ~85mm cover that are face/top-nailed instead need two fixings per joist, but that is a different, visible method.)

Split the room into rectangles and enter each one as its own section using the Add section button; the calculator adds the sections together for you. Board counts and board rows are worked out per section and rounded up before being added, which covers the extra cuts where rows stop and restart at the junction between sections and never under-orders. Secret nail counts use each section's own rows and run length, while adhesive and underlay are worked out from the combined floor area. Use three sections for a T or U shaped room.

Popular widths for solid wood are 100–150mm. Wider boards (150mm+) are more prone to cupping and require more careful moisture management. Narrow boards are more stable and traditional.

Yes. Leave a 12–15mm expansion gap around all walls, pipes and fixed objects. Solid wood expands more than engineered wood, especially across the grain. Cover gaps with skirting or scotia.