Cost to Fix rising damp

May 29, 2019
Cost to Plaster a Wall – A

Find out the typical cost of different types of damp treatment so you know how much you should be paying to stop damp in its tracks.

Repairing your home's damp problem can be expensive. Here we look at typical costs and give you expert advice to make sure you don't end up spending more than you need to.

Damp proofing costs can run into thousands of pounds, as the most extreme remedial works significantly affect your home's structure and may be the only solution if you want to banish damp for good.

Costs for dealing with damp

We've worked with the Royal Institution of Chartered Surveyors, which publishes average building work and repair costs, to bring you the average cost for a range of different damp treatments, from repairing a damp-proof course with silicone to laying an entirely new damp-proof membrane.

And to give you a more realistic idea of what treatments might cost you, we've provided prices for terraced, semi-detached and detached houses, as well as the costs for treating just one wall or one area.

Which? members can log in now to see all the prices in the tables below, as well as findings from our damp investigation, which revealed bad practice from a number of damp specialist companies.

If you're not a Which? member, you can gain instant access to all this information, and our investigation findings, with a £1 trial subscription to Which?.

Table notes: Costs correct April 2016.

Table notes: Costs correct April 2016. Injecting silicone involves drilling into the walls. Inserting a DPC (Hessian-based bitumen in this case) would involve cutting two courses into the brickwork, inserting the new DPC, pointing in mortar and restoring the brickwork to make it look like it did before.

Table notes: Costs correct April 2016. This work includes cutting out three bricks and renewing them to match the existing.

Table notes: Costs correct April 2016. Where a cavity tray or damp proof barrier is inserted, the cost includes removing bricks, replacing them and making them match the existing bricks. The damp-proof barrier/course is added in the coping area. The costs for the cavity trays quoted are made from polypropylene. The stepped one is also made from led.

Table notes: Costs correct April 2016. The material used for sealing the walls in this case is asphalt, a thick liquid. Jobs quoted above include removing old plaster, clearing out joints and brickwork/blockwork, applying three cots of asphalt tanking, rendering (with cement and sand), refixing or installing new skirting and decorating.

Table notes: Costs correct April 2016. Membrane used in this case is 500 gauge bitumen coated polyethylene.

About these costs

To arrive at the average prices above, RICS uses cost data from its Building Cost Information Service (BCIS) database, where costs are collated from a variety of sources and analysed.

Material costs are based on the best trade prices from a range of suppliers across the UK, which are then benchmarked to reveal the best national average. Labour rates are based on the current Building and Allied Trades Joint Industrial Council wage agreement.

Damp jargon buster

We've explained some of the common damp treatment terms below, but it's also worth visiting our pages on condensation, rising damp and penetrating damp for more details.

Damp jargon buster
Word or phrase Explanation
Damp-proof course (DPC) A horizontal strip, often made from plastic or bitumen felts, built into the wall at the height of at least 15cm above ground level.
Damp-proof membrane (DPM) A sheet of material, impervious to water, laid under the concrete floor. This should be connected with the damp-proof course so that the house is effectively sealed and protected from ground water.
Silicone damp-proof barrier Instead of inserting a new damp-proof course, silicone is sometimes injected into a wall to create a barrier.
Cavity tray Used in a cavity wall to act as a way to drain any water away from the inner wall to the outside through 'weep' holes (holes in a part of the outer wall). These are usually used around places where something 'interrupts' the wall, such as windows. These come in many different forms, depending on where they are in the wall, and made of many different materials.
Tanking Covering an entire damp area, such as a whole wall or floor, in damp-proof material (either a membrane or liquid), to effectively 'seal' the area and protect it from moisture.

Get professional damp-proofing help if needed

Many of the problems and solutions above require specialist help. So to make sure you're not overcharged, you should get quotes from at least three companies (some do charge for a damp report, but you get this back if you use the company) and seek advice from an independent damp specialist if there are inconsistencies in the work recommended.

That way, you'll find out whether or not the treatment is absolutely necessary and will be able to weed out any firms that charge over the odds.

In our undercover damp-proofing investigation (see below), we found that households could be spending hundreds of pounds on unnecessary damp-proofing treatment.

Damp-proofing investigation

In a snapshot assessment in 2012, Which? invited 11 damp-proofing companies to two houses with a total of three potential damp problems. These visits were then analysed by three damp-proofing experts, who found that in two thirds of cases the companies recommended unnecessary or inappropriate treatment, or missed the problem completely.

Five of the 11 damp companies that visited the first property recommended completely unnecessary treatment according to the experts – some costing as much as £1, 440 – when essentially they should have suggested asking a plumber to fix a leak.

In the second property, only two of the 11 companies recommended a suitable solution for the penetrating damp problem in the hallway. In this property five companies also failed to notice the likely damp penetration/rising damp problem at the front of the house. Of those who did identify it, only four recommended a suitable treatment.

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