Waterproofing ICF Constructions using Type A, B and C waterproofing systems


The crucial elements of a successful waterproofing solution for the below ground elements of an ICF basement – or partial ICF basement – are often not fully understood. In particular, there may be a lack of awareness of the naturally unsealed joints between the ICF construction blocks, along with the very important joint position between the concrete slab (or ICF insulated slab system) and the ICF wall system.

Pouring concrete into ICF wall systems provides fantastic structural integrity however can result in hidden areas of concrete under-compaction (known as ‘honeycombing’). This has implications for the functional waterproofing properties of the watertight concrete and, unlike regular formwork concrete, there is no opportunity to remove it and assess as it remains hidden. Any under-compaction areas may only become apparent after completion and backfilling and, if water is not present at the time, sometime later. Therefore, it is essential to specify and install a robust, specified solution (often as a combination) from the very beginning.



Sometimes overlooked is the inclusion of reliable and maintainable buried and hidden land drainage around the base perimeter of earth retaining walls. This is a risk reducing measure, along with the use of combined or dual systems of waterproofing. These measures are laid out in the guidance provided in BS8102 ‘Protection of below ground structures against water from the ground’.

We recommend that you consult Triton at the very earliest stage of your project to enable us to advise on the most appropriate system specification. We have extensive experience with the specification and installation of all types of structural waterproofing including systems used on ICF projects.  Of course, we consider all projects on an individual basis but, as a general guideline, below is what might be included in a ‘typical’ specification for the below ground waterproofing of an ICF construction project. At Triton Systems, we offer any initial guidance and advice free of charge so please do not hesitate to get in touch.



We work closely with several leading ICF construction partners. Please use this link to find out more about our ICF partner companies.


Typical specifications

Below is a typical specification for below ground ICF waterproofing:

Type A membrane – Triton Hydrolock beneath the slab with self-adhesive Triton TWS EX100 external to the wall sections.

Type B concrete infill – concrete containing Triton TT Admix to reduce free lime being carried through any cracks or under-compacted areas in the concrete infill into the type C system (leading to higher maintenance costs) and to help prevent internal lime staining. Advice is available on the correct concrete mix to use for best results.

Type C – Triton Platon cavity membrane system installed internally, along with appropriate drainage channels etc.

These three systems can simply combine to form a robust ‘gearing’ function, initially stopping water ingress externally via the self-adhesive wall membrane and pre-applied slab membrane/watertight concrete and then managing away any water that does get through primary systems via the internal cavity drain system. There are several external membrane options available depending on the need for ‘waterproofing only’ requirements, or waterproofing and gas tightness protection combined. Combined or dual forms of waterproofing, with or without gas barrier protection are used where the consequences of failure or leaks is not acceptable, usually where the space is intended for habitable use.

If small dimensional allowances are made during the early design stages of an ICF build then no loss of any internal floor space is necessary – we can advise on these details.

See below for a typical detail showing the Triton ICF waterproofing solution. This is also downloadable at the bottom of this page, along with a general installation guide and datasheets relating to the products referred to above.

For further information and to discuss your individual project please contact us on info@tritonsystems.co.uk or call us on 01322 318830. We offer free structural waterproofing project reviews and we encourage you to get in touch to discuss your project at the earliest possible opportunity.