1. Boards and Decking

We recommend using only OSB3 T&G 18mm 8’x2’ boarding:



All Matrix distributors (and some timber yards and builders’ merchants) stock 8x2 18mm OSB3 T&G boards and it is worth making every effort to find a local source. If you are unable to obtain them use 18mm OSB3 boards or WBP plywood.
If you use 8x4 square edge boards be prepared to:

Note: The bandaged joint will be clearly visible on the finished surface of the laminate

Preparing the Deck


Laying T&G boards


Rebating the trim into the deck

The thickness of trim and additional CSM bandage may capture a small amount of standing water at the drip edge on the finished roof. Whilst this has no detrimental effect on the integrity of the roof you may wish to use an electric plane to form a trim/bandage rebate into the board (approx 2mm) to accommodate the trim and bandage.

Ply and PU insulation board

PU insulation is available with 6mm plywood glued to one side. Although It would seem reasonable to fix it PU side down and apply the GRP to the 6mm ply, as the resin cures it shrinks and the 6mm ply is not stiff enough to prevent curling and the panel will dish. If however you use it ply-side-down and fix an 18mm T&G OSB 3 board on top of the insulation (fixed through to the beams) you will be able to apply the laminate without distortion.

For more information see the Warm Roof construction section

Next section: Estimating >