“6 × 3” is the traditional imperial designation for timber formerly supplied at 6 inches by 3 inches. Since the UK’s transition to metric, timber is specified in millimetres.
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Nominal imperial size: 6" × 3" (≈ 152.4 × 76.2 mm)
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Nominal metric reference: 150 × 75 mm
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Typical finished/regularised size after drying and planing:
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Regularised carcassing: ≈ 72 mm × 145–148 mm
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Planed (PSE/PAR): ≈ 69–72 mm × 144–147 mm
(Actual supplied dimensions vary by mill, grading, moisture content, and finish.)
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The legacy “6×3” label remains in trade use, but specifications, drawings, and cutting lists should be based on the metric finished size. For tight tolerances or when matching existing work, measure the section supplied. If used structurally, confirm the grade (e.g., C16/C24). Lengths are supplied in metres.