How much does rising damp treatment cost? (2026 prices)

First: are you sure it is rising damp?

Rising damp is moisture that climbs from the ground through the pores of the wall, as if through a wick. It is real and common in old masonry houses, but it is also the most oversold diagnosis — because it is the most expensive treatment.

Three signs together make it likely: a damp band up to about 1 metre from the floor, white salts (efflorescence) and crumbling plaster, on a ground floor or in a basement. If the patch is in the upper corners, behind furniture or gets worse on winter mornings, condensation is far more likely.

Before asking for quotes, take the free diagnosis: 12 questions and a probability for each cause. If confidence is low, the result recommends a technical visit — which is also a useful answer.

How much does rising damp treatment cost per m²?

Observed prices for injections and electro-osmosis range from €35 to €60 per m² of treated wall. New plaster, when needed, is almost always quoted separately.

The ranges were collected from Google.pt, cume.pt, Habitissimo, Zaask and customer reports published in October 2026. The marketplaces contradict each other — Zaask quotes €4–50/m², Habitissimo an average of €157.50/m² — which shows how opaque this market is.

How a rising damp quote is built

A serious quote starts from measurements, not a fixed price «per house». Four variables explain almost all the difference between quotes.

• Area in m²: length of affected wall × height to be treated. The height usually goes a little above the tide mark to catch the salty zone.
• Wall thickness and material: an irregular 50 cm stone wall takes far more product and more holes than a 15 cm brick wall. Some firms charge per linear metre and adjust for thickness — ask for the unit in writing.
• One face or both: on an interior wall damp on both sides, or an exterior wall where the outside render is also redone, the area to treat or plaster doubles.
• Plaster and finishes: hacking off old salty plaster, applying salt-retardant plaster, painting with breathable paint and removing rubble. This part can cost as much as the barrier itself.

Then come site factors: difficult access, built-in furniture, tiles to remove, kitchens and bathrooms with pipes in the wall. None of this is unusual, but it should be itemised, not buried in a total.

Worked example: a 4 m × 1 m band on two walls

Picture a ground-floor flat in a 1960s building with the typical tide mark: 1 metre high along 4 metres, on two living-room walls. The arithmetic goes like this:

For this case the barrier should, as a rule, land between about €280 and €960, depending on the price per m² and the number of faces. Salt-retardant plaster and painting come on top and depend on material and finish — ask for them on a separate line.

A quote of several thousand euros for these two walls is not automatically excessive: it may include outside drainage, plaster on both faces or thick stone walls. But you should be able to see, line by line, where the difference comes from.

When it isn't worth treating

If the wall is damp only behind a wardrobe pushed against it, if the outside ground is higher than the inside floor, or if there is a pipe in the wall, no injection will fix it. Fix the cheap things first: move furniture away, clear gutters, lower the soil against the façade, look for leaks.

Basements and ground floors often have more than one cause at once — see the guide on damp in basements and ground floors.

Red flags in a quote

• Rising damp diagnosed above the ground floor, or on patches on the ceiling and upper corners.
• No measurement mentioned: just a «visual inspection» or a device nobody explains.
• Only a total, with no area in m² and no price per m².
• A discount «valid today only» or pressure to sign during the visit.
• A guarantee that is only verbal, or conditional on paid annual servicing.
• Plaster and paint left out when the wall is visibly damaged.
• No sign of an alvará or certificado de empreiteiro (contractor licence issued by IMPIC) or of insurance.

Many companies do the visit for free and sell their own system — the diagnosis and the works come from the same source. It is neither illegal nor necessarily bad, but it is a good reason to get another opinion. See also how to choose a damp-proofing company.

Guarantees: what to read before signing

Guarantees of 20–30 years are common in this market, but the number of years says little without the conditions. Read the guarantee as a contract, because that is what it is.

• What it covers: damp returning in the treated zone, the plaster, the paint, or just the product?
• How failure is proven: who measures, with what device, and who pays for the call-out.
• What voids it: painting with impermeable paint, not replacing the plaster, later building work.
• Who honours it if the company closes, and whether it passes to the new owner if you sell.

Questions to ask before accepting a quote

1. What type of damp did you find and how did you measure it (contact moisture meter, carbide method, thermal imaging)?
2. What is the area in m² and the price per m²? Does it count one face of the wall or both?
3. Does it include hacking off old plaster, salt-retardant plaster, painting and rubble removal?
4. How long should the wall take to dry, and when can it be painted?
5. What does the written guarantee say, and what voids it?
6. Why this method and not another? Compare with the guide injections vs electro-osmosis vs plaster.

Get 2 quotes for different methods and run both through these questions. If you already have a quote in hand, you can use our free second opinion, which automatically checks whether the method and price per m² fit the type of damp.