How to Waterproof Expansion Joints

An expansion joint (also referred to as a movement joint) is a planned joint which is designed to allow two sections of concrete or masonry to expand and contract.  This structural gap between adjacent parts of a structure allows for safe and inconsequential relative movement of those parts, which can be caused by thermal variations, creep (a phenomenon which causes a redistribution of stress away from points of intensity), shrinkage, ground settlement or other conditions.

All concrete and reinforced concrete once placed, will contract slightly during the curing process due to the nature of the material.

Expansion joints are incredibly useful when laying new concrete or reinforced concrete within an area bounded by walls or buildings, as they allow the concrete to expand and/or contract without transferring pressure onto other structures, which potentially could cause cracks within the concrete slab or the wall.

The design of the joint is important for the overall design and function of a structure and its recommended design and construction should be kept as simple as possible.

The key function of waterproofing an expansion joint is to minimize water ingress into a structure by creating a secure waterproofing barrier.  Penetrating water may cause damage and may reduce the usage and lifecycle of the building.

Ensuring the selected waterproofing barrier can accommodate the anticipated joint opening is critical to the long-term success of a waterproofing application.  An inadequately waterproofed joint can lead to openings which will allow for moisture infiltration.

Expansion joints can be vertical or horizontal.  For both horizontal and vertical joints, care must be taken to ensure that the layer of fresh concrete adjacent to the joint is adequately compacted.

Any structure with numerous expansion joints will be susceptible to leaks/water ingress as this is classed as a “weak point” in the structure.

It is important when waterproofing an expansion joint to apply a durable material which will permanently adhere to the joint flanks, maintain flexibility and, in some cases, may need to be restrained.

Application of the waterproofing barrier should follow the manufacturers’ requirements for materials and application methods.

Expansion joint waterproofing can be incorporated at the design stage or retrofitted for failed systems.

Delta Membrane Systems Limited provides all kinds of joint sealing solutions – why not contact our Technical Department for advice and product specification.

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