Following the recent storms that caused damage across the UK and the increased risk of floods, ensuring properties are waterproof will no doubt be high on the list of priorities for homeowners, renters and construction teams.
Waterproofing is one of the most important facets of a building as it can help to improve the durability of many different surfaces. There are a variety of waterproofing materials available for walls, roofs and floors, but not all materials are suitable for all purposes and – without the right type of waterproofing – a building project can run into major problems. So it’s crucial to know what materials are right for the job.
This guide highlights the waterproofing materials that are available, and the benefits they bring if used properly when carrying out work.
Waterproofing materials for walls and floors
Materials for walls and floors must offer more than just protection against water. They also need to act as a barrier to air and vapour to stop moisture from getting trapped under the insulation, or within the masonry and carpentry, which can result in mould, fungi or mildew. Fortunately, there are three key waterproofing materials that can help with this.
Watertight Concrete: Classed as Type B waterproofing, this relies on the new structure being constructed using watertight concrete with the addition of additives within the concrete. The concrete for the purposes of providing an integral waterproofing system should be in accordance with BS EN 1992 Eurocode 2 and waterproofing admixture should be compliant with BS EN 934, and in accordance with both Table 1 and Section 9 of BS 8102:2009.
Pros: given concrete is usually specified in the construction of new retained structures, it can be a cost-effective way to utilise the structure itself as part of the waterproofing design.
Cons: it requires correct design and careful construction to avoid permeable concrete and honeycombing through lack of compaction; contamination of, or cold, construction joints or cracking due to thermal contraction and shrinkage.
Cementitious Coating: Classed as Type A waterproofing, this is a coating that usually consists of sand, organic and inorganic chemicals, alongside waterproof/crystalline substances. The active ingredients are combined with lime, which starts a hydration reaction that results in a waterproof seal. This material is used for a wide range of applications – from creating a waterproof seal over concrete structures such as walkways and foundations, to treating water-retaining structures like tanks and concrete tunnels. This can also be used alongside watertight concrete or Polypropylene membranes to lock structures down and manage groundwater ingress.
Pros: this type of coating is typically easy to use and work with. If used correctly, it will provide a durable watertight seal that can last for many years. It can provide corrosion resistance to substrates and protection from the effects of aggressive acid gases, moisture and chlorides. The product is also available in a spray format, which is useful for larger surfaces.
Cons: despite being easy to apply, cementitious coating tends to lack flexibility. Whilst concrete can flex, compress and stretch, it does so minimally, so bear this in mind when applying the coating. It also should not be punctured.
Polypropylene Membrane: Classed as Type C waterproofing, this offers an alternative or an addition to watertight concrete/cementitious coatings when waterproofing structures, and is considered the failsafe approach if designed correctly. By using an impermeable high-density Polypropylene membrane with an 8mm stud height to walls and a 20mm stud height to floors, it forms a cavity when fixed to the walls and floors – hence it being known as a Cavity Drain Membrane which acts as a drained waterproofing system. As opposed to traditional tanking that holds back water and pressure, a Cavity Drainage Membrane is designed to allow moisture in behind the membrane, allowing it to depressurise, so it can be diverted and sent via hidden drainage channels to a drainage point. Once the membrane has been fitted, walls can also be plastered or dry lined directly.
Pros: Cavity Drain Membranes do not impose any load onto walls. The air gap behind the membrane can allow the walls to breathe and helps a structure to dry out. They are versatile and flexible, and can be easy to install to brickwork, blockwork or concrete walls.
Cons: it takes great care and skill to ensure the system is designed, installed and sealed properly so that moisture, dampness and smells don’t penetrate into the room. This option also comes with more upkeep, as you should arrange for the system to be maintained and checked by a professional at least every six to twelve months.
Waterproofing materials for roofs, balconies and terraces
The roof is often a vulnerable part of a building that is susceptible to water infiltration. Generally speaking, roofing materials are waterproof but often this isn’t enough to keep out the moisture given the intense inclement weather that the area can be subjected to. Therefore, it’s necessary to put in place additional waterproofing measures to ensure your roof can last for decades.
For balcony and terraces, waterproofing materials must have specific characteristics such as being resistant to UV rays and being flexible. This is because these areas undergo slight movements due to changes in temperature, which would cause rigid waterproofing materials to crack.
The following materials are commonly used for these areas:
EPDM Rubber – this is available in membranes with a thickness of ideally 2mm to 6mm. The key benefit to this synthetic rubber material is its flexibility and capability to expand and contract with temperature changes, which is crucial for roof waterproofing. EPDM can be formulated to be resistant to temperatures as high as 150 degrees celsius.
Rubberised Asphalt – this is a very tough and flexible material that can provide great protection against a variety of weather conditions. It also dries within three to four hours after application.
Bituminous Membrane – as a versatile, easy to apply material, this is recommended for both commercial and residential buildings and particularly those with low slope roofs. It’s a sticky and viscous substance with strong endurance, made from a mix of organic liquids. However, as it’s made from crude oil it’s not the most eco-friendly waterproofing material. As the adhesion properties of the membrane decrease over time, it can also have a low shelf life.
PVC Waterproofing Membrane – this is a popular product for roofs as it’s water and vapour-permeable, meaning that it can let moisture out of the roof space of a building. It can also be reinforced to offer extra durability, and is easy to install. It has a unique product formula, which enables it to have a long lifespan ranging from 30 to 50 years.
There are a multitude of domestic and commercial options for structural waterproofing that can help to provide buildings with extra protection. It’s recommended that you consult a professional who can advise on which waterproofing material is best to use for your space, and for your budget. Peter Cox has applied various waterproofing solutions to projects ranging from domestic renovations to large commercial works such as car parks, tunnels and new builds. Find out more about our services here.