Delta supplies combination waterproofing for large London new build

Products from Delta Membranes were recently chosen to create a waterproofing solution for a large new build, single storey structure with a basement which would offer both residential and commercial use to a development in West London.

Advance Property Preservation Limited was approached to provide a waterproofing solution, with the basement area accommodating both commercial and residential units, as well as the upper floor. The warranty provider requested 2 forms of waterproofing be incorporated into the design to the front retaining walls of the structure.

When specifying the most appropriate method of waterproofing for a new-build basement it is advisable to follow the recommendations within BS 8102:2009 ‘Code of Practice for Protection of Below Ground Structures Against Water from the Ground’. The standard advises on the types of waterproofing available and confirms the performance grade to be achieved. This project required Grade 3 protection – no dampness or water penetration acceptable.

The waterproofing method adopted for this new-build basement required careful consideration to ensure the system was as effective as possible to maximise the potential use of the basement, as well as the maintenance of the drainage elements of the waterproofing system.

Phase 1 of the project involved power pressure washing the basement walls prior to an application of Koster Polysil TG 500 an anti-lime inhibitor. With two coats of Koster NB 1 grey being applied to the retaining walls which were lapped to the ceiling and floor slab. Koster NB 1 with its crystallizing minerals were employed to seal against pressurized water (> 13 bar) and is classified as a Type A (Barrier Waterproofing) System. This mineral coating waterproofing slurry contains capillary-plugging agents making it an ideal solution to protect the structure from ground moisture ingress, for non-pressurized and pressurized water.

Phase 2 then saw the incorporation of a combination of a maintainable modular/ sub slab and perimeter drainage system into the ground bearing basement slab in association with the Cavity Drain Membrane System and the basement floor was levelled to no more than 1-10mm.  The reason for levelling the basement floor to no more than 1-10mm is to reduce associated risks of water ponding or pooling beneath the Cavity Drainage System, which could potentially cause flotation stress to come to bear too.

In addition, 48 Linear Meters of Delta Drainage Channel was incorporated into the basement floor area of the project, accumulating to 250 m2. The all-important access ports to the Delta Channel were incorporated at regular intervals for future maintenance purposes, which is a vital aspect of internally applied Type C Cavity Drained Membrane Systems to keep running to their optimum. 

Then, 120 m2 of retaining walls to the structure were linked to the Drainage System to ensure any weak points (floor/wall junctions) were adequately protected from any potential water ingress.

To finalize the twin waterproofing system, Delta MS 500 membrane was applied to the basement walls and Delta MS 20 membrane was applied to the basement slab.

A Type C Cavity Drain system is made up of cuspated membranes which are applied to the walls and floor of a basement with a channel incorporated at the wall/floor junction. The cavity drain membrane allows any water ingress to filter down to the slab and find its way to the perimeter channel. The channel directs any water ingress to a sump pump or agreed drainage points which is situated below the slab (floor). The sump pump chamber will then remove any water ingress to the ground level drains.

Finally, the lower internal, non-earth retained walls then received a DPC (damp-proof course) to act as a barrier through to prevent moisture rising by capillary action such as rising damp. The DPC was linked to the Type C system ensuring the structure was adequately protected.

Overall, Advance Property Preservation Limited was able to offer empirical results on this project, from site attendance to methodology and installation, and the customer was delighted with the project and Advance’s professional and logical approach. 

Delta Membrane Systems,
Delta House,
Merlin Way,
North Weald,
Epping,
Essex,
CM16 6HR
United Kingdom

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