The DIY Fix is reader supported. When you buy after clicking a link on our site, we may earn an affiliate commission.
One of the most commonly asked questions when it comes to damp in a property is: Can you damp proof a single brick wall? It’s a common problem for a few very simple reasons. Firstly, any single brick wall, by its very nature, is going to be more prone to penetrating damp and condensation. This is likely to be even more of a problem where the wall is external. It’s a common issue in many older properties and on extensions. These often have only a single skin to save space.
The simple answer to the question is: Yes, you can damp proof a brick wall. However, the best course of action isn’t cut and dried. The best solution depends on a variety of factors. For example, dealing with a single brick wall that is already affected by damp; or damp proofing as a preventative measure. Broadly speaking, there are three ways to damp proof a single brick wall:
- ‘Board and batten’ over the surface of the wall
- Build an internal wall and cavity wall
- Apply a damp proof membrane to the wall
It’s important to realise that none of the above methods will provide a perfect solution in every situation. However, if you choose the most appropriate method for the job, you should be able to damp proof a single brick wall successfully.
What if your no good at DIY?
For those who want to do the work themselves, we have some more detailed info below. However, if you are not a keen DIY’er, you may want to hire a proffesional, to help get your damp proofing done correctly.
One of the best way to do this, is hiring via a comparison site. When you do this, you can get multiple local quotes from rated damp proofing experts in your area. As a results the quotes tend to be very competative and you can read reviews on the companies. Also, most companies will offer a free damp survey before you hire them.
In our experience the best comparison service for damp proofing experts is a site called Bark. We have seen discounts as high as 60%.
For those looking to do the work themselves, let’s look at the three approaches you can use to damp proof a single brick wall.
Board and batten over the wall’s surface
This approach is a relatively straightforward and affordable option. It involves removing any existing plaster so that the brickwork is exposed. A couple of coats of tanking slurry should then be applied. Tanking slurry is something of a secret weapon when it comes to damp proofing. It’s very effective in preventing mould from appearing and from stopping water ingress in its tracks. To learn more you can read our full tanking slurry case study here
Next, treated batten can be attached to the wall. Drill holes should be filled with silicone. 25mm insulation boards can then be fitted to the battens. The next stage of the process is to fit plywood (typically 12mm or 18mm). Finally, plasterboard can be added to the ply. Leave a 10mm gap from the floor and skim.
On the plus side, nothing should come through the wall. The insulation board is particularly useful too. This warms the face of the interior wall. The result is that the possibility of condensation forming is greatly reduced. This alone should not be sniffed at, as a single brick external wall is pretty much guaranteed to suffer problems with condensation at some point. Condensation is often overlooked and in all honesty it’s an even more common problem than damp itself.
On the negative side, board and batten is best used on newer brickwork. It has a tendency to decay on masonry that is old and damp. It also needs to be effectively treated and ventilated or dry and damp rot can rear its ugly head.
Build an internal wall and cavity wall
A cavity wall is essentially when two separate walls are built to fulfil the purpose of a single wall. The outer wall is known as the external leaf. The inner wall is called the internal leaf. Meanwhile, the space between the two walls is known as the cavity.
The other basic requirements are that the size of the cavity should be 4-10cm wide. Both the internal and external leaves need to be at least 10mm thick.
Cavity walls offer several advantages over conventional solid walls. For starters, they offer a greater degree of thermal insulation as the space between the two cavity walls fills with air and reduces heat transmission. Cavity walls also offer good protection from moisture. As moisture is not allowed to enter because of the space between the walls, it also prevents dampness. It also stops outer efflorescence – where salt comes to the surface of a wall.
A cavity wall is a particularly good option if loss of space isn’t an issue. This makes a cavity wall a wise choice for the likes of barn conversions. Bear in mind though that the unventilated cavity means that damp can eventually reach the decoration on the inner wall.
Applying a membrane to a single brick wall
A damp membrane is perhaps the most versatile approach to damp proofing a single brick wall. This is the most modern treatment and the most common. There are three main types of membrane: air gap, damp proof, and plastic lining. Basically, they all have the same effect and serve the same purpose. Membranes are dimpled plastic sheeting that offer a barrier of protection lining that is vapour proof.
The membrane can be fixed to block, stone, brick or a rendered surface. Plastic plugs help to form an air cavity. Applying a membrane is a versatile option too. You can choose a plain surface, which can be battened over. Alternatively, a mesh surface is ideal to directly plaster or plaster board over.
Membranes are a great option for both single skin walls and cold walls. And, as single brick walls are always cold, that makes membranes perfect for most situations.
How to install a membrane
Installing a membrane is fairly straightforward. Firstly, the area needs to be cleared of any plugs, bonding timbers and gypsum plaster. It’s important to check whether the area has ever been affected by flooding or if there are any traces of water ‘weeping’ from the wall. A drainage method will be needed, if this is the case.
If you opt for a finishing method of battens and plaster board, you will need to use either a damp proof membrane or an air gap membrane. To apply plasterboard that is dab fixed or to plaster directly onto the surface, choose a mesh membrane. The mesh facing on the membrane serves as a ready-made for direct plastering over. As an alternative, apply adhesive to the membrane and stick plasterboard on top.
Always allow the wall to settle for a period once you have applied your chosen finishing. Check for any evidence of moisture before you complete your final decoration.
Other ways to damp proof a single brick wall
If your single skin wall is affected by damp, the cheapest course of action is to remove the plaster or plasterboard and replace it with foil lined plasterboard. The foil lining must stop before it reaches the floor. Otherwise, any moisture conducts upwards. The foil acts as a preventative barrier, stopping moisture from passing through.
Another option is to apply a damp proof course injection to the affected wall. Painting the wall with a clear waterproofing liquid suitable for brickwork will add a further layer of protection.
Other tips and methods to use
A salt neutraliser is a clear liquid applied to plaster or masonry. As the name suggests, the liquid neutralises salts. This is a good method to adopt to help stop damp or mould damage occurring. You need to apply two coats and wet in between each coat with fresh water. If your single brick wall is damaged, apply a salt neutraliser coating.
Chemical and Cream Damp Proof Courses (DPC)
Chemical or cream damp proof courses are the best course of action if the existing/original damp proof course (DPC) has become compromised.
3 solutions to any problem
Broadly speaking, you can see that there are three main solutions for the typical problems that you are likely to encounter in terms of damp proofing a single brick wall. Whilst it’s probably fair to say than there is no single solution that operates as the perfect answer to every problem.
However, it’s also fair to say that there are a number of options that you can choose to address the issue of damp proofing a single skin wall. The reassuring thing to be taken from all of this is that one thing is crystal clear. Whatever the individual problem of damp in a single brick wall, there is a solution out there.
We hope you found this information useful. If you have any questions please post them in the comments below.