*White Foam, **Black Fibre

Expansion and contraction is one of the most critical aspects of any glass block construction. Expansion joints must be incorporated to the perimeter of all glass block panels (as detailed on GBT data sheets). *For the head and jambs of any specification a 10mm thick foam should be used. It is extremely important not to bridge this expansion joint in mortar, it should be caulked over using silicone. If the joint is bridged, it may cause blocks to crack.

Cills should be prepared by using either a **bitumen strip or two coats of bitumen emulsion, to allow for compression caused by the weight of the panel yet ensuring that the base course of glass block mortar does not adhere to the substrate.

When the height or width of the panel exceeds 6m, either a vertical or horizontal support should be incorporated, or a horizontal or vertical slip joint. (See data sheets GBT 0009 and GBT/0010).

For curved glass block walls, expansion joints must be inserted around the perimeter and where the curve changes plane. (See datasheets GBT 0017).