Basement Construction

MacLennan Waterproofing provide several levels of specification for basement construction.

Every form of basement construction has different waterproofing requirements. The waterproofing designer should agree from the beginning of the design process what the form of construction will be, and should advise on the implications , risks, and waterproofing requirements of each form and method of construction under consideration.

Typical Section through Reinforced ICF Retaining wall (Toe)

Construction type: Concrete & Waterproofing Existing Basements

Concrete basement construction and existing basements / remedial work. You may consider just a cavity drain system inside a concrete structure built to BS 8110. This system is guaranteed for 10 years against any ingress of water to the inside of a well-constructed basement with correctly installed joins and details such as service entries...

This is a single waterproofing system so is not acceptable to many building insurers. The cavity drain on its own is often the only option for older historic basements or basements built of masonry. A correctly designed system can be used and guaranteed in constantly flooding basements.

Find out more about Waterproofing Existing Structures

Construction Type: Concrete & New Build Basements

Most new build basements have to have two forms of waterproofing. It is a requirement of insurance companies and has to be considered under BS8102 for habitable structures. For concrete basements where two forms of waterproofing are required, waterproofing with flexiproof or cement based tanking is carried out to construction joins and honey combing; these being the major routes for water ingress into concrete basements.

Hydrophilic joins are difficult to detail and often dislodged during concrete pouring and pokering. External or internal protection with applied flexible rubber or internally cement based coatings prevents water ingress into joins. Any water ingress is stopped with resin injection. Once all detailing has been repaired the concrete is waterproofed with crystal coat, a post applied waterproofing agent.

Find out more about Waterproofing New Build Basements

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Typical detail through Base of retaining wall

Concrete Block Work & ICF

For these forms of construction we would apply full external waterproofing. This provides protection to the structure externally making it as water tight as possible. This is achieved by the installation of applied membranes or spray applied coatings. There are advantages and disadvantages which are discussed prior to specification. Protection of the waterproofing is provided with Insudrain. Insudrain is a 50mm insulation system unique to MacLennan with a drainage form against the wall.

It provides insulation, protection and drainage for the same cost as either insulation or drainage. If the basement is to be built of concrete block work, or insulated formwork then external waterproofing has to be applied in addition to the internal cavity drain system. External waterproofing cannot be carried out as a standalone system.

Learn more about External Waterproofing

Construction on a site suffering from ground gas

This level of protection is water and gas protection and is achieved by positive air ventilation and sealed membranes or external gas tight membranes.

Having worked in the industry for over 30 years, our team of specialists know this industry inside out. With experience in multiple industry disciplines, our team offer an outstanding full end-to-end service. You can rest assured that MacLennan ensure every job is carried out to the highest standard, and that all designs and manual work are executed according with the relevant legislation to guarantee the structures safety and efficiency.

Learn more about Gas & Waterproofing

Why should I work with MacLennan?


We Design, supply and install. There's no split responsibility with MacLennan.


MacLennan live and breathe waterproofing, have a look at one of our free CPD seminars and find out!


MacLennan has the most comprehensive guarantees and insurances in the industry.

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