Stop damp in its tracks. Discover the typical cost of damp treatment and damp proofing

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Repairing a damp problem can be expensive. Here we look at typical damp treatment and damp proofing costs plus expert advice to make sure you don’t end up spending more than you need to. Although damp proofing costs can run into thousands of pounds and be very disruptive, some types of damp can treated very cheaply or even free of charge.

How much does damp proofing cost?

We’ve worked with the Royal Institution of Chartered Surveyors (RICS), 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.

To give a more realistic idea of how much various 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. Bear in mind that costs will vary regionally, so will depend on where you live.

The tables below show approximately what you should expect to pay for some typical solutions to rising and penetrating damp.

Before you decide which type of treatment you need, take a look at our pages on dealing with how to stop condensation, rising damp and penetrating damp, so you can fully understand what each treatment involves and what circumstances it would be used for.

That way you’ll know what’s right for your home and won’t spend more than you need to.

Problem: the existing damp-proof course is below ground level

Solution: excavate as much soil as is needed to ensure the ground level is at least 15cm below the damp-proof course.

Problem: walls are damp at a low level because the damp-proof course is damaged or non-existent

Solution: create a damp barrier with silicone or insert new damp-proof course. To add a new damp course (DPC), two courses of brickwork will be cut out and a bitumen-coated hessian damp-proof course inserted. Then the brickwork will be made good, including the mortar pointing, so that it looks like it did before.

Problem: damp is penetrating a cavity wall

Solution: clear blocked cavities. This can be done from the outside, by cutting out three bricks, clearing the blocked cavities and any mortar droppings and then renewing the bricks so that they match the rest of the wall.

Problem: damp is penetrating walls at different heights, around windows and doors, and at ceiling height

Solution: insert a damp proof course in the walls at different levels to create a barrier to damp. Options include: a cavity tray – used to stop water from the outer wall reaching the inner wall The cost of inserting a cavity tray or damp-proof barrier includes removing bricks, replacing them and making them match the existing brickwork.

Problem: damp is penetrating the walls because exterior surfaces are damaged

Solution: apply waterproof paint to exterior walls to stop damp coming through. This can be painted onto brickwork, concrete and rendered surfaces.

Problem: internal walls are damp

Solution: ‘seal’ the walls (often called tanking) with damp-proofing material.

The material used to seal the walls in the prices below is asphalt, a thick liquid.

The prices include removing the old plaster, clearing out the joints in the brickwork/blockwork, applying three coats of asphalt tanking, rendering the walls (with cement and sand), refixing or installing new skirting boards to match the existing ones and decorating the wall.

Problem: damp floors

Solution: ‘seal’ the floor (often called tanking) with damp-proofing material.

There are two options: bitumen-coated polyethylene membrane or mastic asphalt tanking. Both jobs priced below involve removing the flooring, the screed (concrete under the floor) and skirting from the room.

Then either bitumen-coated polyethylene membrane and priming or two coats of asphalt tanking are laid before reinstating the screed and refixing the skirting boards.

Problem: kitchen or bathroom walls are damp

Solution: install an extractor fan in an external wall.

Damp-proofing cost data

To calculate 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.

Everything needed to carry out the work is included in the costs such as labour, materials, any preliminary work, contractor overheads and profit, and VAT. Materials 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. RICS then uses this data in a standardised model of the average double glazed window and door types and sizes. Data copyright RICS 2020 and reproduced with permission. Data is current as of October 2021.

Don’t pay for unnecessary damp treatment

Damp can be a complex issue, and there can sometimes be more than one solution. The most expensive cure might not be the only option, or you may be able to do something yourself that costs very little.

For example, condensation damp is reasonably easy to sort out and can often be dealt with by simply opening windows more often, not drying clothes indoors, turning your heating on more, fitting vents or installing bathroom and kitchen extractor fans.

With penetrating damp, something as simple as clearing your gutters can also help. We’ve heard from many  members who have tackled damp problems themselves, particularly condensation and some types of penetrating damp.  One said: ‘I cleared the blocked gutter myself.

It was a 10-minute job.’ Another said: ‘It was a simple issue of a tile that had come loose and I could fix that myself.’ Rising damp can be the most expensive type of damp to fix.

Fortunately, it’s one of the least common kinds of damp.  Without letting your damp problem become too serious (damp can wreak havoc on building structures), it’s worth taking a little time to monitor it so you can work out what the cause might be.

You could use this time to try out a few cheap or free treatments before you call in a specialist.


Professional damp-proofing specialists

If you do decide to call in a professional, 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 that’s been suggested.

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