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The weather in London in 2021 was particularly wet, or so it felt in a property in Leyton, East London, where, after a particularly heavy dose of rainfall, the owners came down to discover the basement was inches deep in dirty flood water.

The damage was extensive due to the original cement-based tanking not being fit for purpose. The walls, floor areas, and internal timber stud walls were all heavily damaged and would require complete refurbishment. However, it was crucial to first address structural issues to ensure that the potential of future flooding was quashed.

Finding a permanent solution for a full refurbishment

The property owner’s insurance company agreed to cover the cost of the remedial work up to the height of 1.2m from the floor level, and this included the full gamut of works from the strip out to the decorated finish.

Garratt’s Damp and Timber were called in to discuss the best approach to protecting the property from further ingress, and it was decided that with the probability of moderate water ingress, reoccurring in the future, a cavity drain membrane system that adhered to the most recent British Standards relating to waterproof substructures – BS8102:2022 Type C – would provide a permanent solution.

What does BS8102:2022 mean for the client?

BS8102:2022 is the leading global standard that governs the ways to deal with and prevent water ingress from surrounding ground into a structure below ground level. Compliance ensured that Garratt’s solution covered all the following requirements:

  • Evaluation of groundwater conditions
  • Risk assessments
  • Options for drainage outside the structure
  • Waterproofing barrier materials applied to the structure
  • Structurally integral watertight construction
  • Drained cavity construction

With works agreed and funding in place, Garratt’s came in to initially prepare the area. The damaged stud walls, door frames, and doors were removed for disposal, and the area was cleared. The insurers had already been in with air driers to get rid of the worst of the damp.

Preparing the groundwork for the membrane and cavities

Recesses were then dug into the slab around the perimeter of the raised footings, and purpose-made drainage channels extruded in white plastic were installed. These are designed to sit below the cavity drain membrane and feed into the sump and pump chamber.

A recess was dug for the sump and pump chamber. During excavation, the hole is regularly filled with groundwater. This was evidence that the best solution was a cavity drain membrane system – so instead of fighting against the water, the system instead took control of it and redirected it accordingly. It would not affect the final tanked environment in any way.

Once the walls were prepared and stripped of any loose materials, Garratt’s started to apply the cavity drain membrane. This was fixed to the walls with waterproof sealing wall plugs, wrapped around exposed footings, and then lapped to sit on top of the drainage channels. The joins were then sealed.

Flood testing

Having created a ‘tank’, it needed testing. If working correctly, any water ingress would be contained beyond the membrane, and excess water pumped out to an external drain via the sump pump. Garratt’s flood testing the tank. Results indicated that no leaks appeared on the dry side of the membrane tank, and the pump operated efficiently and discharged the water.

Now onto the fun stuff

Having secured the tanking structure against water ingress, the fun work of refurbishing the basement into a viable, useable room could start. Metal tracking was fixed to the membrane via the waterproof wall plugs that were originally used to secure the membrane, and plasterboard was fitted to these tracks. The membrane-covered footings were covered over using plywood boxwork, and then the whole thing room was plastered and skimmed.

The floor, which did not require a waterproof membrane, received an application of a two-part epoxy resin damp proofing treatment.

Garratt’s then handed over to Alexander Henry Building and Maintenance, who completed all the plumbing and electrical works, laid the laminate flooring, fitted the bathrooms, and painted and decorated.

A happy customer all round

The result is the creation of a suite of rooms, including a bathroom, which can be used for any number of purposes with confidence and peace of mind. Equally, the tanking works satisfy the insurers and will help to boost the value of the property overall.

If you have a concerning issue regarding the waterproofing of a basement or cellar, contact Garratt’s now to discuss your requirements.


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