Structural Waterproofing& Tanking in Harrow

A cementitious tanking system is a polymer-modified, sand and cement based slurry or multi-coat render applied directly to prepared masonry or concrete, forming a barrier that resists water under pressure. It bonds to the substrate, which means the substrate must be sound, clean and free of old paint, bitumen and friable render before application.

Barrier tanking suits structures in good condition where the finish needs to be solid, walls that will be plastered and decorated, or areas where the room dimensions cannot afford the build-up of a membrane system. It relies completely on detailing: wall-to-floor fillets, service penetrations, steps and reveals all have to be formed correctly, and a single missed junction is where water will find its way through.

A cavity drain membrane is a studded high-density polyethylene sheet fixed to the wall with sealed plugs and tapes. Water reaching the structure runs down behind the studs into a perimeter drainage channel and away to a sump chamber with a pump, or to gravity drainage where levels allow. The membrane is not trying to hold water back; it is redirecting it.

This approach tolerates a wetter, less predictable structure and remains serviceable, which is why it is the common choice for basement conversions and older brick cellars and vaults. Wall membranes can be dry-lined or plastered over with a meshed membrane, and floor membranes sit under a screed or a floating floor build-up.

Where water cannot discharge by gravity, a sump chamber and pump handle it. Specification decisions include pump capacity for the volumes expected, twin pumps or a battery backup where failure would flood a habitable room, and a discharge route that is both legal and practical.

Externally, the volume of water arriving can often be reduced first: clearing and repairing rainwater goods, correcting ground falls away from the building, and repairing external drainage all cut the load on the system inside.

Turning a cellar into a habitable room brings in more than waterproofing: floor levels and headroom, insulation, ventilation, drainage for a WC or utility, electrics and escape routes all interact with the system chosen. Waterproofing is designed first, because every other element is fixed to or through it.

Where a conversion is part of a bigger project, we can carry out the associated building, plastering and remedial work alongside the waterproofing so one contractor is responsible for the sequence rather than three.

Domestic work covers Victorian cellars, basement flats, vaults under pavements, garages and store rooms. Commercial work covers basement plant rooms, storage areas, retail stockrooms and offices, where protecting stock and equipment and keeping the premises trading shape the programme.

In both cases the technical answer is the same: identify the water conditions, specify a barrier or drained system accordingly, detail it properly, and back it with guarantees.

There are no published prices, because the variables are large: area of wall and floor, condition of the substrate, whether pumping is required, how much preparation and removal of previous coatings is needed, access for materials and spoil, and the finish specified.

The free survey produces a written fixed price for a defined system and scope, so you can see exactly what is included before committing.