Ply subfloor unsupported at doorway

wassupjg · 2025-12-08T19:05:47+0000

18mm ply subfloor next to patio door threshold unsupported as joists fall short of 400mm width area (left of green line; cavity with rockwool), any way to support from underneath to stop plywood flexing when stepped on?

Alastairreid · 2025-12-08T21:03:34+0000

Take the insulation out, line the cavity with dpm and backfill with concrete.

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Ply subfloor unsupported at doorway

wassupjg

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Alastairreid

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