5 x 2 inch treated timber
“5 × 2” is the traditional imperial designation for timber formerly supplied at 5 inches by 2 inches. Since the UK’s switch to metric, timber is specified in millimetres.
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Nominal imperial size: 5" × 2" (≈ 127 × 50.8 mm)
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Nominal metric reference: 125 × 50 mm (often written 125 × 47/50 mm)
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Typical finished/regularised size after drying and planing:
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Regularised carcassing: ≈ 47 × 125 mm (sometimes ≈ 45 × 120–123 mm)
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Planed (PSE/PAR): ≈ 44–47 mm × 118–121 mm
(Actual supplied dimensions vary by mill, grading, moisture content, and finish.)
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The “5×2” label persists in trade use, but specifications, drawings, and cutting lists should rely 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 sold in metres.
