What is the best way to deal with rising damp in an older house - damp proof course or something else?

[Rory_39]

I bought a Victorian terraced house last year and I have damp patches appearing on two of the ground floor internal walls. A damp surveyor quoted me £3500 for an injected chemical damp proof course. A different builder told me the existing DPC might be fine and the problem could be something else entirely. The patches are about 300mm up from the floor and the plaster is starting to bubble. What should I actually do and who should I believe?

[RedKnight]

Get a second and third survey from surveyors who charge for the survey rather than free surveys from companies who also sell the treatment. Free surveys from remediation companies have a strong incentive to recommend the most expensive solution. An independent RICS-qualified surveyor charging 200 to £300 for a proper report is worth every pound

[Phil7]

If injection treatment genuinely is needed the 3,500 quote might be reasonable but get three quotes. The technique has been criticised in academic literature as less effective than marketed and some independent research suggests lime plaster renovation addresses the visible problem as effectively as injection treatment in many cases

[PhotonBurst16]

The builder who questioned the DPC diagnosis is potentially right. Damp in Victorian terraced houses is very commonly caused by bridged DPCs from raised external ground levels, blocked air bricks in suspended timber floors or failed render rather than a defective DPC. Each of those is cheaper to fix than injection treatment

[Sigma]

Check the external ground level relative to the DPC height first. If the soil, path or paving around the house has built up over the years above the DPC level then moisture is bridging directly over the existing DPC regardless of its condition. Lowering the external ground level costs almost nothing

[GoldbergFan_X]

Check the air bricks at the base of your external walls. Victorian houses have suspended timber ground floors that need ventilation underneath. Blocked air bricks cause moisture to build up under the floor and migrate into the walls in exactly the pattern you are describing. Clearing or adding air bricks is a twenty pound fix if that is the cause

[Highland Dylan]

Rising damp in the classic sense - moisture actively wicking up from below the DPC through the masonry - is less common than the remediation industry suggests. Many cases diagnosed as rising damp are actually penetrating damp from external sources or condensation. An independent thermographic survey can distinguish between moisture sources much more accurately than a visual inspection