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    Below grade waterproofing

    Underground structures also need to be resistant to penetration by liquids and chemicals. This is to protect and extend the life of the structure.


    Properly prepare the surface to be treated. Apply a primer, note that each surface requires its own specific primer.

    For a rough surface, place a levelling layer with POLYAC® 55.

    On top of this, place a white or colourless waterproof POLYAC® BDM coat. This can be the manual version POLYAC® BDM-M/AL or the sprayed POLYAC® BDM-HD version.


    After one hour (depending on the ambient temperature), apply the 2nd coat of POLYAC® BDM-M/AL or POLYAC® BDM-HD. This serves to protect the waterproof membrane.

    Choose to apply the 2nd layer in a different colour than the 1st. This is to ensure good coverage of the first layer when applied and to distinguish the waterproof layer from the protective layer when inspecting the surface later.