A Danrae Guide to Expansion Joint Waterproofing

Building with escalator and stairs

At Danrae Group, our expansive waterproofing services span diagnostic, solution design and post-project preventative maintenance. Our team has decades of experience, so we understand end-to-end waterproofing requirements – and we pride ourselves on our attention to detail.

Waterproofing for expansion joints requires a solid knowledge of waterproofing for construction and best-practice solutions for strata, construction, civil, government and commercial properties.

Here’s our guide to waterproofing expansion joints to ensure an effective and efficient waterproofing solution.

Wood placed between concrete blocks on the wall

About expansion joints


An expansion joint is a mid-structure gap or separation used to alleviate stress on building foundations caused by structural movement. This movement may occur due to varying factors such as strong winds, earthquakes or tremors and static or live load deflection. Structures also commonly expand and contract in temperature extremes. Expansion joints compress in heat and contract when a structure cools.

Expansion joints bisect all components of a building, including foundation floors and walls, balconies, planter boxes and rooftops.

There are two categories of expansion joints. Vertical expansion joints are cut into walls and horizontal expansion joints are in floors. Both fulfil the same function, which is to allow for normal structural shifts without cracking.

Waterproofing expansion joints


There are several types of expansion joints found in construction, including foam seals, compression seal systems, metal cover plate systems, roof bellows systems, reinforced vapour-barrier systems and waterproof, fire-resistant joint systems.

An expansion joint is crucial for building integrity, but it may also be a source of moisture or water ingress if the expansion joint system does not meet stringent standards. This infiltration may damage both the joint and the surrounding materials.

Expansion joints as such need to be filled with an expansion joint system that allows for thermal, environmental and load structural movement, that is resistant to water ingress, and that meets other construction requirements such as fireproofing or soundproofing.

Pile of Expansion Joint and Rebar Grid on a construction site

Techniques for expansion joint waterproofing


Typically, on vertical applications, we apply a waterproofing membrane and/or reinforced flashing material over the opening and at least four inches up the vertical substrate. We fully adhere the flashing to both vertical and horizontal substrates.

On horizontal applications, we lay the membrane over the substrate and overlap the joints by a minimum of three inches at each side.

Horizontal expansion joints are particularly prone to leakage, so we design a tailored waterproofing solution to ensure they are watertight and provide adequate drainage away from the expansion joint.

Expertise for effective waterproofing


The importance of effective expansion joint waterproofing shouldn’t be overlooked. Like other aspects of a building, including basements, lift shafts, balconies and rooftop gardens, effective solution design and delivery are imperative to ensure waterproofing integrity across the entire property.

As expansion joint systems may comprise multiple elements, including concrete, wood framing, steel studs and decking, multiple tradespeople may be required.

At Danrae Group, we ensure the quality of our waterproofing solutions by looking after every stage of diagnostic, design and remediation with our dedicated team of waterproofers, project managers and trades specialists, including builders, carpenters and tilers.

If you need expert expansion joint waterproofing, please contact us.

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