Damp Proofing External Walls

Common in construction projects, waterproofing from the outside can sometimes be the most appropriate solution

DAMP PROOFING External Walls

Damp proofing external walls is most common when a property is under construction. However, exterior waterproofing can be applied to existing buildings, but it usually requires exterior excavation.

Before damp proofing external walls, you must dig down to the foundations, creating a large, deep trench around your property. This means that anything that hinders excavation has to be removed - Including pavements, groundwork, and landscaping.

When this trench has been excavated, a suitable basement waterproofing treatment is then applied to the foundation walls, either in the form of a membrane or a cementitious render (traditionally known as tanking).

Additionally, to relieve external water pressure, a drain is installed around the bottom of the foundations. This is called a ‘French drain’.

French drains are pipes filled with holes or slots. They are laid at the base of the excavated trench and crushed stone is packed around the French drain before the excavated soil is replaced on top. The French drain works by collecting any excess water in the soil that seeps through the layer of crushed stone and into the drain. The drain then directs the excess water away from the building.

More information on French drains

WHAT ARE Problems with DAMP Proofing EXTERNAL WALLS? 

 (click on images above for hi-res version)

Although exterior basement waterproofing has been the norm in property development for a long period of time, there are problems associated with it. French drains with inadequate filters will eventually let mud, sand, and sediment into the pipe, and over time this will clog up and block the drain. If the water cannot get through the French drain it will eventually find an alternative route to flow; usually through your basement.

Exterior basement waterproofing systems also require a lot of excavation if/when they need to be serviced or repaired. This is obviously a large job and not one that many homeowners or businesses want to deal with.

Despite the potential drawbacks listed above, exterior waterproofing can be essential for certain construction jobs (building into the side of a hill for example), and can even work in conjunction with internal waterproofing systems to provide a perfect waterproofing balance. 

Other methods of basement waterproofing

Take a look at some alternative methods of basement waterproofing including modern interior waterproofing systems and traditional tanking.

Interior waterproofing

Interior basement waterproofing is the most modern method to waterproof a basement. Also, waterproofing from the inside is comparatively cost-effective and simple.

Interior waterproofing


Tanking, with a waterproof cement or slurry, is one of the oldest methods of holding water back from underground spaces. This traditional method can still be very effective.

More about Tanking

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