Damp proofing is a term used to describe several techniques deployed by professionals to prevent moisture from penetrating or rising into a home.
The most popular methods are wall injections, waterproof tanking and surface sealants.
The prices you’ll see on this page are for wall injections, which are often referred to as injected chemical damp proof courses.
If your property is suffering from rising damp and you would like an idea of how much damp proofing costs, this page is for you.
We can also help you get a competitive price that’s based on the specifications of your home.
The last time we updated the prices on this page was on the
About This Damp Proofing Cost Guide
Back in 2014 we got in touch with over 20 specialists and asked them to provide us with a cost to damp proof a wall that was showing signs of rising damp.
In 2018 we repeated the process and updated our research with new figures that reflect the current industry prices.
Further down this page, you’ll see the results of our findings, we’ve published an average price for chemical wall injections.
We think our guide is a great resource for those wanting to budget their home improvement finances. Don’t forget; this is just one of the hundreds of projects we’ve researched, our full price list can be found here.
What Do You Get For Your Money?
After we got in touch with our chosen damp specialists, we asked them to put in writing everything they had told us.
We wanted detailed written quotes so we could create this page.
While each firm offered us slightly different advice, the list below sums up what we think a typical written quote should contain:
- Full inspection of walls with damp meter and other testing equipment.
- A visual inspection of walls, damp course etc and a diagram produced.
- The removal of skirting boards and areas of damaged plaster to the internal walls.
- The injection of waterproof chemicals into both internal and external walls to create a new damp course.
- Waterproof sealer, known as tanking, painted onto the internal wall.
- Finish off with gypsum moisture resistant plasterboard and plaster to internal walls.
The Cost to Damp Proof Walls
We asked our chosen contractors to provide us with two prices.
The first was for damp proof injecting into the walls but excluding any tanking or plastering work. We stated that we would like to do that work ourselves.
The second quote was for the damp proof injecting, tanking to several internal walls and also replastering to some internal walls as well.
Project 1) Inject Liquid Chemical Sealer to Create a New Damp Proof Course
This price is for a 2-bed semi detached property located in Surrey.
The project is for a pro to inject a damp proofing chemical liquid into the external walls. No internal plastering or finishing off work is quoted for.
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Project 2) New Chemical Injected DPC to External Walls and Repairs to Internal Walls
This project is for the chemical injection into external walls of a 2-bed house. Extensive damp patches of plaster are to be removed from internal walls up to a height of 1.5metres, the walls will then be sealed and replastered.
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- Provide specifics of your damp problem
- Get a written quote in a timely manner
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- Leave your own feedback upon project completion
Tips and Advice From The Professionals
When sourcing quotes from professional damp proofers, we asked lots of probing questions about where damp comes from and how the suggested treatments work.
Below you’ll find a handy write-up with detailed information gleaned from the pros.
How is the Chemical DPC Inserted Into the Wall?
Most modern walls are constructed with a plastic sheet between the bricks near the ground. This prevents moisture from rising through the wall and soaking into the internal plaster:
If the walls of your house don’t have a plastic sheet or it has failed, a professional can inject a chemical waterproofing liquid directly into the bricks.
The chemical is injected into drilled holes which are around 12mm in diameter. The porous bricks soak up the waterproofer and the entire process is fairly quick and not too disruptive:
If the internal walls are showing signs of damp, the plaster may need to be removed and a waterproof tanking applied. The walls are then replastered. This aspect of the project is time-consuming, messy and costly.
How much plaster you need to strip off will determine how much the project costs. There is a big difference between removing a few small areas of plaster and removing all of it, which would be a major project.
There are many different ways to inject the waterproof chemicals into a brick wall. Some specialists use a high-pressure system, others prefer a drip-feed system that lets the bricks to soak up the liquid over a 48 hour period.
Newer systems involve creams that are squeezed into the pre-drilled 12mm holes.
The best system for your home will depend on the type of bricks the wall is constructed from.
Causes of Damp Walls
Rising damp isn’t the only cause of damp walls and there’s a good chance your walls can be fixed without the need for costly wall treatments.
Here are the most common causes of damp problems:
- The flower bed has been raised so the moist soil is now above the protective damp proof course.
- The patio or concrete floor was constructed above the damp proof course, rendering it ineffective.
- Rainwater from roof gutters is discharging or overflowing near the wall where it breaches the DPC.
- The external wall is poorly rendered so the mortar “bridges” the DPC.
In all of the four examples above, the solution isn’t to install a new DPC but to:
- Dig out the raised flower beds.
- Lower the patio or put in a drainage channel next to the wall so water is channelled away from the wall.
- Make sure rainwater discharged from guttering cannot splash onto the wall above the DPC and keep the gutters maintained and cleaned frequently.
- Remove any external mortar render that’s bridged the DPC.
Why is Damp Proofing so Expensive?
The wall injection itself isn’t time-consuming or costly, but the plastering and making good of the walls certainly is.
Damp proofing can also a very messy and disruptive project and you will probably want to move out of the house for a few days at least.
Is There a DIY Option?
It is certainly possible for anyone with a basic understanding of DIY to insert a chemical DPC into an external wall.
12mm holes are first drilled 3/4 of the way through the brick course just above the existing DPC or 150mm above the ground level. Each hole is spaced at 100mm intervals.
A cream or liquid is then squeezed into the holes via a mastic application gun. A small amount of mortar is then used to plug the gap.
The more difficult part of the project is the internal walls. If the moisture is on the internal wall, the plaster may need to be stripped off and replaced, a job that is more suited to the professionals.
If the homeowner has a limited budget, they could try and seal only the walls, then wait and check the results. If the internal plaster isn’t too badly damaged then it may dry out and be suitable for redecorating.
If you’ve never seen a chemical DPC being injected into a wall, you may find the video below informative:
You Should Avoid Doing This:
If you are on a tight budget you might be tempted to paint the interior walls with a waterproof paint/sealant to mask any signs of damp.
While this may seem a logical and practical step, it is, in fact, one of the worst things you can do.
If moisture is still present in the wall and the underlying issues haven’t been resolved, then the damp will likely spread behind the sealant and this can lead to:
- Further damage either vertically or horizontally.
- The plaster, bricks, floor joists and render may fail as it never has the chance to dry out.
- Damp odours and smells will persist.
As a general rule of thumb; walls should only be coated with a waterproof sealant if you are 100% certain that there is no damp rising from the ground below. Otherwise you are just masking the issue by sealing the moisture into the wall where it will spread and damage the materials used in the construction of the wall.
Get a Price For Your Damp Proofing Project Here
We think our research into damp proofing and prices is a great resource but as every project is different, we suggest sourcing your own quotes that are based on the specifications of your home.
Tap the button below to see how we can help you source a great price for damp wall proofing.
- Send in details of your damp proofing project.
- Arrange a site visit from an experienced inspector.
- Receive your written quote in a timely manner.
- Check ratings and reviews posted online by recent customers.
- Leave your own feedback upon project completion.