BASEMENT WATERPROOFING

Transforming Damp Cellars & Basements

Problem
Walls and floors in rooms below ground level are subject to lateral damp penetration by either hydrostatic pressure or capillary action. However using specialist basement waterproofing techniques, basements,cellars and vaults can be transformed into habitable accommodation and this can add considerable value to commercial and residential buildings in urban areas where high property values prevail.

Solution - Basement Waterproofing

Cavity Drainage Membrane

The cavity drainage system of basement waterproofing uses a high density studded plastic membrane acting as a dry lining to the walls, ceilings and floors with an air gap behind. This allows for the free movement of water which is channelled into a drainage system for evacuation outside the building.

Regardless of whether free water is present, all membrane joints and junctions are designed to accommodate water removal behind the lining either through natural drainage or a sump and pump installation. The membrane is fixed with waterproofing plugs and the floor / wall junction is sealed using a proprietary jointing compound.

The internal wall finishes can be either a plasterboard dry lining system or plastering direct on to the membrane. The floor finish is either screeded or timber boarded.

The principal drainage channel is installed around the perimeter of the room bedded in to a rebate at the wall floor junction. This can be either a flexible perforated conduit fitted with an outer geotextile filter or alternatively a rigid plastic unit with maintenance access ports.

Sumps & Pumps

In most circumstances Peter Cox recommend the inclusion of a dual drainage system with two submersible float activated pumps fitted into a preformed sump chamber and complete with built in non-return valves.

Water is collected from the floor channels through the clear opening at the top of the unit. The two pumps are usually set at different levels with one acting as standby. Sumps are fitted with a sealed access cover which facilitates maintenance and servicing checks. As part of the standard commissioning routine, systems are flood tested to confirm operational integrity before the access cover is sealed.

Installations that comply with BS8102 carry a 10 year basement waterproofing guarantee.

Dry Lining System (without drainage)

A ventilated dry lining system can be installed without full drainage provision in order to give protection from damp or salt contamination. However it will not resist water pressure and so cannot be guaranteed waterproof.

Cementitious Multi-Coat Render

An alternative to the CDM system, this is the traditional method of basement waterproofing using multiple coats of render with a waterproofing agent in a dense sand/cement mix applied by spray, brush and trowel to the walls and floor. This technique is also commonly known as "tanking".

Thorough preparation is critical, as the wall has to be bush hammered first to remove any loose material and establish a sound key. Special provision has to be made for fixing points to avoid puncturing the waterproof membrane. A choice of finish is available.