How Much Does it Cost to Damp Proof a Wall?
Damp Proofing Prices Updated For 2021
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Did you know that in 99% of cases, damp problems can be solved by simple, low-cost solutions such as improving ventilation, unblocking existing vents, fixing leaks and making sure rainwater in the garden stays away from the wall?
Damp proofing prices aren’t cheap and often run into the thousands, but for most people, they are an unnecessary treatment.
On this page, we’ll tell you how much damp proofing costs but first we would like to go through the common causes of damp and how to solve them without breaking the bank.
The good news is that every suggestion on this page is cheaper than costly damp proofing. Many of the suggestions you can carry out yourself for free.
You have nothing to lose by going through this checklist, but it could save you a fortune.
Step 1 – Check For Penetrating Damp
Penetrating damp isn’t the same as rising damp although they are often confused.
Instead of paying for expensive damp proofing, try finding the source of the moisture and resolve the problem there.
Here are some examples of very common issues that can lead to penetrating damp.
Get these checked before you gather prices for damp proofing.
1a – Check the Roof For Broken Tiles
Roof tiles often slip or break, usually as a result of the freeze/thaw process but occasionally for other reasons.
In many cases of damp, rainwater enters the roof and runs long the loft felt and into the cavity, it may appear as damp patches anywhere on the wall including on the ground floor.
Solution: Check the roof and have any repairs carried out.
Resource: See how much it costs to replace broken roof tiles here.
1b – Check the Chimney
Chimneys are prone to leaking, they are lashed with more rain than any other part of the property.
Leaks may create damp patches anywhere on the wall, including near the base of the chimney.
Solution: Check the chimney cowls, flaunching, brickwork and leadwork for leaks.
Resource: See how much scaffolding costs here and FixMyRoof has a great guide (with photos) to fixing common chimney leaks.
1c – Check the Roof Gutters
This is a very common cause of wall damp.
If the gutters are leaking then rainwater can splash onto the external wall near to the ground level. It can then soak through the wall and damp or mould may appear on the internal walls. The water could also soak under the wall and floors, causing more damp to appear.
If the gutters aren’t leaking but are overflowing due to leaves and twigs etc blocking them, then a considerable amount of water could be splashing onto the wall or soaking the area under the wall.
Solution: Check the guttering and have any repairs or cleaning carried out.
Resource: See how much gutter cleaning costs here.
1d – Check Pipes For Leaks
A few years ago a friend told me a story about how she was quoted over £6000 for damp proofing when the problem was actually urine.
Yes, you read that correctly; piss.
The flat upstairs had a leaky toilet and the wastewater leaked into the cavity and soaked the base of her walls and also slightly under the floor too.
A damp-proofing “specialist” misdiagnosed the problem as rising damp and quoted over £6000 to inject a chemical into the wall to stop the urine soaking up the walls.
Not only was this an unnecessary treatment but it would have utterly failed to stop the urine from soaking under her floor.
The toilet upstairs was fixed and the downstairs walls were replastered with the cost recovered from the home insurance – problem solved.
There are dozens of places water can leak from:
- Fresh water pipes in the garden or home.
- Wastewater pipes and drains inside as well as outside.
- Bath and sinks, inc overflows.
- Radiators pipes.
- Water tanks and overflows.
Solution: Check all pipework in the home and garden.
1e – Make Sure Patios, Decking and Soil Isn’t Higher Than the Damp Course
This is another very common cause of wall damp and often rears its ugly head after some garden improvement works.
The damp proof course acts as a barrier stopping moisture from soaking up the walls but there should be 150mm between the course and the ground outside.
The images below may help to explain how it works:
Common reasons for rainwater entering the wall above the damp course and causing damp internal walls:
- A new patio or path has been laid and there’s no longer 150mm between the course and the ground.
- Decking has been installed too high.
- A flowerbed has been created next to the wall and is too high.
- Stored items are creating a bridge over the damp course.
- A shed has been installed and rainwater flows off the roof into the wall above the damp course.
All of the above can cause wall damp, but the problem can be exasperated by leaking roofs and gutters.
Damp proofing the wall will not solve the problem, although it may mask it for a while.
Solution: Check the damp course hasn’t been breached if necessary, lower the outside ground level.
Resource: The Paving Expert has a very detailed guide on damp proof courses and how to keep rainwater away from the wall.
1f – Check Rainwater From Driveways and Patios Isn’t Flowing Towards the House
I have seen a case where rainwater from a poorly installed DIY patio was flowing towards the house and the sheer amount of water caused damp problems.
Rather than paying for costly damp proofing, a drainage channel was installed to collect the water and take it to an existing soakaway under the garden.
The issue could have been prevented by having the patio laid by a professional in the first place.
Solution: Ensure rainwater flows away from the wall and where that’s not possible, install and maintain drainage.
Resource: Our guide to driveway prices and drainage options is a good place to start.
1g – Check Brickwork and Render
On wind and rainswept walls, the mortar between the brick or the render could have come loose, washed-out or cracked, leading to water ingress.
When water finds its way through a wall, damp may appear at the point of entry or nearer to ground level.
Wall rendering isn’t cheap but done properly should keep the water out. Brick repointing is another task that might need doing on older properties with soft crumby mortar or on newer houses due to poor workmanship.
Solution: Check brickwork or wall render for missing, crumbling, cracked or washed-out mortar.
Resource: Wall rendering isn’t cheap but our house rendering price guide is here.
Step 2 – Condensation Checklist
Condensation isn’t always visible as it can appear under floorboards, behind wallpaper and in lofts but it can cause damp patches on walls and ceilings, rot timbers and degrade bricks and mortar.
Damp proofing a wall will not cure condensation problems, ventilation is often the best course of action although why there’s so much moisture in the home should also be addressed.
Here is a checklist for the most common causes of condensation damp.
There is no point in getting a price for damp proofing if any of these apply:
2a – Check The Loft
For damp patches on or near to ceilings, check the loft for signs of excessive condensation.
Small amounts of loft condensation are normal in winter, especially during freezing spells of weather but it should disappear when the temperature rises.
If it doesn’t, then there are two things to check.
1) If you have insulation placed directly above the ceiling, check that it isn’t blocking any existing ventilation at the eaves (the lowest part of the roof). You can also install these very cheap DIY vents that help to improve ventilation and disperse any moist air:
2) Check that there aren’t any pipes leaking, tanks overflowing or if you have a heated tank in the loft, that the thermostat hasn’t failed. Sometimes faulty thermostats can result in the tank heater boiling water continuously and producing steam.
External Resource: This is by far the most comprehensive guide to loft condensation we could find.
2b – Check Windows
Old windows usually aren’t airtight; they allow a small trickle of air into the house that helps to push out moist air.
When old windows are replaced with new sealed Upvc double or triple glazed windows, it’s not uncommon for the consumer to notice condensation or damp around the window or on the ceiling above the window. This usually occurs in the bedroom, kitchen or bathroom and almost exclusively during the winter when it’s cold.
The solution is to install window trickle vents such as this:
If damp patches are located near to the windows but are very isolated and few/far between, it’s with checking that there isn’t any insulation missing as this can create cold spots on the walls and ceilings.
Incorrectly fitted windows can create cold spots next to the frame where condensation, mould and damp may form.
External Resource: How to install a window trickle vent (video).
2c – Check The Exterior Walls
Older period dwellings aren’t designed to be airtight. In fact, they’re designed to breathe.
If you or the previous occupant of the property has made changes to the external wall, this could trap moisture in the home. Excess moisture will condensate on cold surfaces such as walls where damp and mould may then appear.
If your older, period property has damp walls, here’s what to check:
- Has the external wall been rendered recently? Did they use breathable materials or something else like sand/cement?
- Has the external brickwork been repointed recently? On older period dwellings, the mortar should be breathable lime-based mortar and not sand/cement which traps moisture.
- Has the exterior wall been painted recently? How breathable was the paint? Most masonry paints are breathable (to some degree) but many aren’t. How many layers of paint are on the externals walls? Decades of wall painting can result in several layers of paint that trap moisture in a building that was meant to breathe.
Solution: On period properties, check the external walls for incorrect use of paints or cement-based mortars. Seek the advice of a specialist who understands the importance of breathability, especially in older buildings.
Resources: The first video below shows damp and condensation caused by incorrect use of cement on the external walls of an older house. The second video shows cracks and water ingress from cement on a period property.
2d – Check The Internal Walls
Most modern homes are built with non-breathable gypsum plasterboard on the walls and ceiling, and that’s just fine.
However, older homes that are designed to breathe are usually built with lime-based, breathable plasterboard and plaster.
Placing non-breathable plasterboard onto the walls of an older house designed to breathe will increase the amount of moisture in the home and cause condensation and damp.
Common reasons why gypsum plasterboard is misused on period dwellings:
- A home improvement or repair carried out by a tradesperson who doesn’t understand the importance of breathability in period properties.
- A damp proofing specialist who has incorrectly diagnosed “rising damp” and has tried to seal the wall with waterproof materials such as gypsum plasterboard, tanking or chemicals.
Solution: Seek the advice of an independent specialist who understands the importance of breathability in period dwellings. Remove the non-breathable plasterboard and any tanking etc. and allow the property to breathe.
External Resource: Grenspec- the important of breathability in older homes.
Employing cement based mortars and renders, ‘plastic’ paints and waterproof sealants can prove disastrous. Moisture is trapped, surfaces break down, damp patches appear and rot and beetle infestation occurs. This may be harmful both to the wellbeing of the building and its occupants.
2e – Inspect Underfloor Vents
On many older homes, the ground floor will be made from timber and will have a void underneath it.
This void must be vented so any moisture under the ground floor can escape. If the vents are blocked, condensation and damp will form, usually at the base of the wall.
The video below shows blocked vents and a patio constructed too high against the wall:
2f – Inspect Internal Appliances and Extractors
Bathroom and kitchen extractor fan vents should be checked to ensure they are working correctly, are not blocked and aren’t spewing out moisture into the home, onto the wall or into the cavity.
Appliances such as tumble dryers should vent their condensation outside and not into the property. Check all venting ducts and pipework are in good order and exit points are not blocked.
Solution: Check sources of moisture in the home and ductwork/extractors are working properly.
2g – Look at The Lifestyle of the Occupants
Some people are very aware of moisture and high humidity levels and will take action such as opening windows, using extractor fans when cooking or after bathing etc.
Unfortunately, many homeowners and tenants do the complete opposite during the winter. Windows are kept closed, extractor fans aren’t used, wet clothes are dried on radiators etc.
Lifestyles can create unusually high amounts of moisture that may condensate and appear as damp patches, especially during the winter.
If all other forms of condensation have been ruled out, consider:
- Upgrading bathroom and kitchen extractor fans.
- Installing a dryer with appropriate ducting/venting, so clothes don’t need to be dried on radiators.
- Installing extra wall vents or window trickle vents.
- As a last resort, and perfect for tenants that refuse to vent the property, consider installing a Passive Input Vent system.
Resource: Tenants not venting their properties and causing excess moisture and condensation is a common issue for landlords.
3 – Rising Damp and Damp Proofing
We’ve put damp proofing and rising damp at the end of this guide for good reason; in 99% of cases, the damp will not be rising and damp proofing won’t be needed.
If you have damp walls from blocked vents – unblock them.
Leaky roof or gutters causing damp walls? – Fix the roof or guttering.
Cement or other materials stopping your period house form breathing? Have them removed.
Unfortunately, the damp-proofing industry in the UK has a very bad reputation. Many companies, although not all, rush into recommending damp proofing products that are costly and in many cases unnecessary.
Damp proofing is a term used to describe any product that is put onto or into a wall to stop damp coming through to the plaster indoors.
If you’ve gone through our checklist and have ruled out all the possible causes of damp, we recommend seeking the advice of an independent surveyor who understands damp, condensation and moisture problems.
Below you’ll find our guide to damping proofing costs.
Here we reveal how much it costs to have a wall damp-proofed.
In early 2021, we had a rare opportunity to source prices from damp proofing specialists in the UK.
A property we had access to in Warwickshire had damp across the bottom of the wall, form one end of the wall to the other.
We contacted 12 damp proofing firms and asked them to investigate.
Below you’ll find the average price for damp proofing but first here’s a breakdown of what work we were told needed doing:
- Take damp and humidity readings prior to any work commencing.
- Remove the skirting boards and dispose of.
- Remove the existing internal plaster to a height of one metre across the wall.
- Install a chemical damp proof course into the wall by way of pressure injection.
- Coat internal walls with a waterproof sealer up to a height of one metre.
- Replaster internal walls with gypsum plasterboard and finish, allow to dry.
- Install new skirting boards.
- Take damp and humidity readings after the work has been completed.
- The customer is responsible for the final redecoration; painting or wallpapering of the walls etc.
Damp Proofing Cost
This is how much damp proofing costs, the price shown is an average of the figures given to us by the 12 firms.
|Location:||Average Price Quoted:|
|Warwickshire||One Wall - £2950|
|Warwickshire||Approx per metre - £425|
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Damp Proofing FAQs
When Was This Damp Proofing Cost Guide Created?
This guide was created with knowledge learned from over 18 years of experience.
The damp proofing prices were sourced in 2021.
Do The Prices on This Page Include VAT?
Yes, all the figures on this page include VAT – Value Added Tax.
Are All Damp Proofing Companies Bad?
No, but the industry has a bad reputation for either miss-selling costly chemical damp proof courses or bundling them in with other works that would cure the damp.
In 99% of cases, damp can be cured without the need for a chemical damp proof course.
We recommend seeking the advice of an independent surveyor who understands damp, moisture and water ingress issues but doesn’t sell or work for any company that sells products. This is the only way to get independent advice.
How Long Does it Take to Damp Proof a Single Wall?
Holes need to be drilled every few inches along the base of the wall and a chemical is injected into the wall.
Drilling holes should take no more than a few hours and the chemical is left overnight to soak into the wall. Expect the external work to be completed in less than one day.
Plastering and making good the internal walls will take longer.
I Have Condensation Problems, Will Wall Damp Proofing Solve it or Make it Worse?
It will either make no difference or if the building is designed to breathe (i.e it’s an older property) it will make it worse as you’re trapping more moisture with the waterproofing.
Are There Any Reputable Trade Associations for the Damp Proofing Industry?
None that are independent of firms that either manufacture, stock, sell or install damp proofing products.
Where Can I Get a Damp Proofing Price Online?
We feel you should seek the advice of an independent surveyor rather than going straight to a damp proofing installer.
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