Bespoke Waterproofing for High-End London Shop Unit

Getting a clearer picture through flood simulation

In order to gain a clear picture of how to permanently waterproof the basement, Garratt’s carried out a flood simulation. This is a study into the points of intrusion of flood water to highlight areas of weakness and provide a foundation for creating a finite waterproofing solution.

The results highlighted that water was entering the basement via defects in the shop front and pavement light wells, travelling along a concealed steel joist and entering the centre of the basement. This presented several complications in finding a solution. The shop was located on a busy street in the centre of Chelsea where traffic was heavy, so replacing the pavement lights was logistically impossible.

The distance that the ingress of water was covering was so widespread that to effectively waterproof the entire area, the complete system had to be customised using a range of different products and processes.

The result was a bespoke waterproofing system that both maintained the integrity of the building and delivered a completely dry, Grade 3 internal environment that met the requirements according to BS 8102, the British Standard, relating to withstanding even the worst circumstances of water pressure and presence in the surrounding area.

Building a Bespoke Solution

The first process was to work with the main contractor, CJS, and remove the shop front to design a bespoke metal bund system that resolved structural defects and prevented further water ingress.

The concrete and steel framework were then treated with sealing primer and finished with three coats of a flexible cementitious waterproofing membrane. The shop front was then restored to the original.

The next stage was the installation of a Newton CDM System, which comprises BBA-approved cavity drain membranes, drainage conduits, sump chambers, pumps, and associated control and telemetry systems.

The dedicated sump chamber houses dual pumps that are controlled and managed by a control unit fitted with a battery backup, which will give additional peace of mind to the tenants who are probably living on the edge every time it rains.

A High-End Solution for a High-End Result

Jack Garratt (CSSW, CSRT) - Consultant Surveyor for Garratt’s Damp and Timber, commented:

“Garratt’s were required to design and install a system to stop high volumes of water penetration through the pavement lights and walls on this tricky project. Replacing the pavement light was out of the question due to the busy street, and water was also penetrating the shop front and migrating along with steels to a point that was impossible to waterproof. Through close collaboration with the experts at Newton, we implemented a full system to withstand any future flooding.”

JN Newton Waterproofing is a UK leading supplier of basement tanking, structural waterproofing, and damp proofing systems. As a Newton-approved installer, Garratt’s has continuous access to the company’s market-leading range of products and training, giving them the confidence and technical knowledge to tackle even the most complex of projects.

The end result was the creation of a dry, ventilated space that was fully refurbished and is now an active part of the tenant’s business. Both the tenant business owner and the building owner have the reassurance that the basement space has been waterproofed to meet the British Standards BS 8102.

Should there be a ‘failure’ in the system installed by Garratt’s, BS8102 stands in as a legally recognised code of practice. To this end, Garratt’s ensures that the products it uses, and the level of workmanship it maintains and expects from all its employees, adhere to these regulations.