Installing a Delta Membrane Waterproofing System in Seven Sisters Road
We have often been involved in construction projects where an issue with groundwater has occurred well into the construction phase. This particular project in Seven Sisters Road was one where the internal fit out was well underway when the flooding occurred.
The property is a large complex of studio apartments, with rooms at the front that were located below ground. The below ground area at the front was originally waterproofed as part of the initial construction and was working well, however further back the ground level was approximately 400 – 600mm below the level of the neighbouring property and was not considered as requiring any waterproofing.
With the internal fit out well under way, the main contractor noted water and dampness was affecting the internal finishes. The screed was removed from the slab and drylining cut back to expose the walls. Once this was done it was possible to see where the water ingress was occurring, through several construction joints where the floor was located below ground level.
Delta Membranes initially visited the property to assess the extent of the issue and propose a waterproofing specification. This was then passed over to us as a Delta Membranes registered installer.
As the concrete slab was already formed, it was decided to surface mount the drainage channels, however as the structure was already built, we had some restrictions with regard to the floor height. Normally with surface mounted channels, we would recommend a 50mm sacrificial screed is laid, leaving a perimeter chase for the installation of perimeter drains. This was not an option here as the overall floor build-up would not allow for an increase of 50mm over and above the insulation and screed requirement.
An alternative to using a screed is to use insulation, however this must be 100% closed cell to ensure it is waterproof. The team at Delta have looked into several products that can reliably be used beneath the membrane and recommended Foamglas. This is a unique closed cell insulation that is bonded to the floor slab, allowing us to surface mount the drainage channels and the main contractor to meet the requirements for insulation thickness and floor build-up.
Application of the Foamglas insulation is a labour intensive task, requiring the use of a bitumen primer coat before the adhesive can be applied and the insulation laid. Once this was down, the Delta MS500 wall membrane was installed with Delta Qwik Seal plugs. The Qwik Seal plugs allowed the main contractor to apply battens without damaging the membrane layer.
Finally the drainage channels and Delta MS20 floor membrane was installed, along with a Delta Dual V3 sump pump system. With the waterproofing complete, the main contractor was able to finish the internal fit out and progress the works without the fear of groundwater issues.