Weather response is particularly useful
A patch that darkens after rain, especially after wind from one direction, points towards external penetration. True rising moisture does not normally switch on and off in step with individual rain events.
Look for a route through the exterior
Open pointing, cracked render, defective sills, overflowing gutters and downpipes can concentrate water into surprisingly small areas. Solid walls are especially dependent on their outer face shedding and then releasing moisture.
Low penetrating damp can imitate rising damp
Rain splash, high paving, defective drainage or a downpipe leak close to ground level can all produce low patches. Height alone therefore cannot settle the diagnosis.
Would you like local contractors to quote?
Give a clear description of the affected wall, the height of the damp and anything that changes after rain. You can then request quotations from local damp-proofing contractors through MyJobQuote.
Get local contractor quotesQuote requests are provided by MyJobQuote, an independent third-party service. Local contractors may respond to your request.