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Timber flooring considerations

Short answer

Timber flooring demands well-seasoned hard timber with moisture below 12-15%, damp-proofing by a ventilated void and DPC, and cross-ventilation. Joists (100x50 mm) are placed at 300-400 mm centres; boards are 20-30 mm thick, tongued-and-grooved, secret-nailed, with a 10-12 mm expansion gap at walls.

Explain things to be considered in timber flooring with figure.

Timber flooring consists of wooden boards, planks or parquet laid over joists or a base. The following must be considered.

  • Choice of timber: well-seasoned, hard, straight-grained timber (sal, teak, sisau, uttis) free from knots and cracks, with a moisture content below 12-15%.
  • Damp protection: the floor must be kept free from ground moisture, so a ventilated void under the joists (air bricks) and a DPC below the wall plates are provided. A clear space of at least 150 mm is kept above the oversite concrete.
  • Ventilation: air bricks in the external walls and a cross-ventilation path to prevent dry rot.
  • Joist size and spacing: joists (e.g. 100 x 50 mm) at 300-400 mm c/c, with spans limited to 2-2.5 m. Strutting or herring-bone bridging is used at mid-span to stop twisting.
  • Boards: 20-30 mm thick and 100-150 mm wide, with tongued-and-grooved (T&G) joints; end joints are staggered and made over a joist.
  • Fixing: secret nailing for a smooth surface; nail heads are punched below the surface.
  • Treatment: preservative and termite treatment of joists and boards; finishing with varnish or polish.
  • Expansion gap: a small gap of 10-12 mm at the walls, covered by the skirting.
   board (T&G)  ==============
   joists       |_|_|_|_|_|_|
   strutting      X  X  X
   wall plate  [==]       [==]
   DPC          --         --
   sleeper wall  |         |

✓ Answer checked by Claude Opus 5.5 (high effort)

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