How to Tank a Cellar – A Step-by-Step Guide

Cellars are fantastic spaces that are, unfortunately, often underused due to persistent damp problems. If you’re looking to create more usable space in your home, why not consider cellar tanking? With the right damp proofing system, your basement could become a home office, games room, storage area, or even your own private cinema!

One of the most effective ways to waterproof a cellar or basement is by using a cavity drain membrane system. This specialist material is designed to form a barrier between your walls and interior space, safely directing any moisture into a drainage system and sump pump so it can be removed before causing damage. At Croft Preservation, we’re trusted experts in cellar tanking across Dorset and Hampshire. Below, we explain how to tank a basement using a professional waterproof membrane system.

There are two main ways to tank a cellar:

• Tanking Slurry (or Coating)
• Cavity Drain Membranes

This guide focuses on the membrane method, which is often the preferred solution for long-term, low-maintenance basement waterproofing. For a comparison of both systems, check out our separate guide on basement tanking methods.

Step-by-Step: How to Tank a Cellar with a Waterproof Membrane

1) Clear the Working Area

Begin by preparing your cellar for the work ahead. Remove any shelves, cupboards, or stored items that might obstruct access to the walls and floor. If you need help at this stage, our team is happy to assist with clearing and preparation.

2) Prepare the Walls

To ensure the membrane can be properly installed, the walls must be stripped back to their original masonry. This includes:

• Removing all paint, render, plaster, and old coatings
• Raking out any loose mortar
• Brushing down to eliminate dust and debris

Check for any cracks, holes, or damaged joints. These should be filled with a suitable fillet seal. If your walls have previously shown signs of salt contamination, it’s wise to apply a salt inhibitor before continuing. This step is essential for ensuring the wall can withstand future water pressure behind the membrane.

3) Cut the Damp Proof Membrane to Size

Using a measuring tape, calculate the total wall surface area and cut your cavity drain membrane to fit from floor to ceiling. Aim for a clean, flush fit to ensure consistent protection across the entire surface.

4) Apply the Membrane to the Walls

Position the membrane flat against the wall. Using a drill, create 10mm holes through the membrane and into the substrate wall behind. These holes will hold the fixing plugs and help secure the membrane firmly in place.

5) Add Quick Seal Plugs

Install specialist quick seal plugs into each drilled hole. These plugs form a tight seal between the wall and membrane, locking it in place and helping to prevent moisture from escaping into your newly protected space.

6) Install the Drainage Channel and Floor Membrane

A drainage channel is fitted at the base of the wall to collect and redirect water away from the internal space. Once installed, a floor membrane is laid over the floor area, pushed neatly over the drainage channel, and sealed against the wall membrane using strip tape to create a fully watertight system.

Call the Cellar Tanking Experts

Tanking a cellar can be a technical and time-consuming task, but that’s where we come in. With over 30 years of experience in cellar tanking and damp proofing across Dorset and Hampshire, Croft Preservation has the knowledge and tools to get it right first time.

Whether you're planning a cellar conversion or just want peace of mind that your basement is fully protected from damp, we can help.

Call us today on 01202 737739 or get in touch online to arrange a cellar survey or discuss your project with our expert team.