Basement & Below Ground Waterproofing in Sydney

Keeping Water Out Below Ground

Below ground structures deal with water pressure from the outside all the time, and once the backfill goes in, the membrane is almost impossible to get back to. Getting it right during construction is far cheaper than trying to fix a leaking basement later.

WSA waterproofs basements, retaining walls, lift pits and below ground walls for builders across Sydney, with membranes, protection and drainage installed in stages to suit the build. For existing basements that are leaking through cracks and joints, we use polyurethane and epoxy crack injection.

FBT Under Slab Membrane System

For new basements, the best time to waterproof is before the concrete goes in. Our FBT under slab system is a pre-applied sheet membrane laid under the slab and against the formwork or retaining structure, so the concrete is poured directly against it and bonds to it.

Once the pour is done, the membrane sits on the outside of the floor slab and concrete walls, keeping ground moisture out of the structure from day one. Because it bonds to the concrete, water can’t track along behind it the way it can with a loose sheet.

It has to be installed before the concrete pour, so we work in with the builder’s program to lay the membrane, detail the laps, penetrations, columns and junctions, and have it ready for the formwork and steel.

Details That Matter Below Ground

Below ground leaks tend to come through the same weak points. These get our full attention:

• Construction joints and slab to wall junctions
• Tie holes, penetrations and service entries
• Membrane protection before backfill so it is not damaged
• Drainage behind the wall to relieve water pressure
• Staged visits as the blockwork goes up
• Compliance certificate issued