Traditionally, a concrete slab would need to cure for about 28 days before waterproofing application can commence. This allows time for the concrete to dry and dispel water vapour and any excess bleed water which can compromise the bond of the membrane to the substrate and cause membrane blistering/delamination.
However, the curing time for concrete before waterproofing membrane application depends on the waterproofing product being used and varies from 24 hours to 28 days.
Many membranes on the market today can be applied after just 7 days of curing as they are designed to tolerate damp substrates and allow water vapour diffusion to dispel water vapour from the concrete which continues to cure.
Further to this, there are special-purpose moisture barriers (usually epoxies such as ARDEX’s WPM 300 HydrEpoxy) which are suitable for very damp substrates and can be applied 24 hours after concrete placement. These epoxy products are usually designed to accommodate over-coating with most waterproofing and decorative coating to allow waterproofing to continue over the freshly poured concrete.
This is a game-changer for expediting the waterproofing process and reducing construction time along the critical path.