Damp Proofing for Floors

Location of the floor

Before you decide to treat a floor for damp, you must identify the location because it can make a huge difference how it is treated.

If the floor is above ground, you can install a Damp Proof Membrane (or DPM).

However, if the issue is in a basement then it’s likely you will require a full tanking or waterproofing system due to a build-up of hydrostatic pressure.

Hydrostatic pressure is when water from the earth outside of a structure presses against the property and causes ingress.

Another factor that influences the type of damp proofing required is the floor covering that is used.

If it needs a sheet membrane, then you will need a heavier covering.

There are two main options when it comes to damp proofing; floor membranes and a liquid-applied floor coating.

Floor membranes

Your first option for damp proofing a floor is a Damp Proof Membrane, or DPM, between the concrete or screen subfloor and the covering.

It’s designed to prevent moisture passing from the concrete or screed to any covering, such as ceramic or quartz tiles, laminate, wood or carpet.

A membrane prevents further damage to the flooring and is designed to last, stopping water ingress for an extended period.

Naturally, a floor that hasn’t been proofed from damp can suffer problems in the future, including damage to the furniture and flooring.

You can tell if a floor already has a DPM by checking its moisture level.

A hand-held moisture meter, approved by damp proofing experts, can do the job.

Make sure the readings you take are accurate, and that your meter has been adequately tested.

As a general rule, if the moisture level is above an accepted level indicated by your flooring manufacturer you should install a damp proof membrane.

That is the only way to know for sure that you’re protected from damp-related issues.

The main type of damp proofing membrane system worth considering is a cavity drainage system.

It is applied internally, and can also be used for below-ground spaces such as basements.

The cavity drain system lies in between the concrete and flooring,  and consists of several small holes that assist with water flow.

The aim of the system, should water penetrate through the concrete, is to redirect the water out of the property to an appropriate outlet – usually a sump and pump system.

If the slab has been damaged, or is in poor condition, the best option is usually to replace it and install a new one.

You could replace the entire damp floor, or isolate the damp from the covering.

That can become a problematic in listed properties where the flooring cannot be removed.

In those cases, a DPM must be laid on top to protect any new floor finish.


Liquid-applied floor coating

The alternative option is to use a liquid-applied floor coating.

They are particularly useful when a floor needs repair or when tiles, carpet or underlay are laid directly onto the floor without tongue and groove floorboards.

Liquid-applied floor coatings are placed directly on the site of dampness, and are then cured to create a water-resistant surface.

These membranes usually consist of epoxy resins, polyaspartic and polyurethane types.

They are ideal because they can be applied directly onto concrete slabs and can be used in a variety of different settings.

The liquid-applied flooring membrane reduces the flow of water vapour and so acts as a barrier to prevent moisture seeping into the floor.

For them to work efficiently, they require a concrete floor thicker than 50mm while the surface needs to be of a good quality without cracks or loose material within it.

Liquid-applied flooring is perfect for larger areas, for example in the warehouse of an industrial unit, because they are more vulnerable to wear and tear.

A finish can also be applied on top of a floor coating depending on the desired end use.


Additional things to consider

There are several extra things worth considering when looking to protect your floor from damp.

First, water can seep into your home incredibly easily even through the tiniest holes or cracks – making them wider than originally.

Of course, that can create a larger problem later.

For that reason, it is important to check a surface thoroughly before putting in a membrane – whether it is a liquid or cavity drainage system.

In the gap between a floor and wall, a silicone caulk should be applied along the edge just like you would when sealing any other joint.

The epoxy resin in a liquid-applied floor coating is usually effective in repairing and filling granite, but it works too with concrete.

Apply it to holes or cracks in your home and the result should be a clear, flat surface that is totally damp and waterproof.

Whoever is doing the job must check a surface is adequately prepared beforehand.

Ensure any debris, previous coatings or surface water is removed.

A poor installation risks causing even more damage that prompts the system to fail.

With that in mind, if you are looking for someone to undertake the work then choose an individual or company with the experience and know-how to complete the task properly.

When finishing a basement, a dehumidifier should be used before the area is sealed, insulated and finished.

This is because it can become damp when coolness in the ground combines with heat from the household.

You will need a DPM under almost all floor finishes, including laminate floors, wood, vinyl and floor tiles.



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