Shower tray former underboarding

Discussion in 'Carpenters' Talk' started by shaneswallow, Jan 29, 2022.

  1. shaneswallow

    shaneswallow New Member


    Looking for some advice please. I need to underboard between joists for an Impey aqua-dec linear 3, 1800x900 shower tray former.

    I only have 50mm depth for runners and the plywood, so I’m thinking 38mm for the runners and 12mm for the plywood to sit on as the ceiling below has exposed joists. I was advised I could get away with 12mm BB or birch faced plywood as its strong vs the usual 18mm. Is this setup ok for the tray to sit on with the joists running perpendicular to the tray at ~450mm centres?

    To make things more interesting, there are already 20mm thick battens nailed to the joists which the ceiling below are nailed into as in attached picture. So 20mm + 25mm runners = 45mm - what would be a good length screw and should there be pilot holes before screwing? The joists are 45mm thick.


    IMG_1852.jpeg Image-3.png

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