Key Take Aways
Penetrating damp—also called rain penetration—is caused when water seeps through cracks, porous bricks or mortar, failed pointing, or defective seals around windows and doors.
Symptoms include damp patches, mould, salt tide marks, crumbling plaster, and aesthetic damage—all of which can compromise structural integrity and indoor air quality.
Diagnosis involves identifying entry points (e.g., cracked pointing or blocked gutters) and correctly diagnosing the type of damp—penetrating, rising, or condensation—to ensure appropriate treatment.
Curing methods include repairing external defects (guttering, cracks, mortar), ensuring proper drainage, applying breathable waterproof coatings, installing damp‑proof courses, and improving ventilation.
Specialised treatments for rising damp may use physical DPCs, chemical cream or liquid injections, damp‑proofing rods, or porous tube systems—though chemical injection or BBA‑certified rods are often preferred.
Additional preventive measures include maintaining good guttering and drainage, keeping landscaping trimmed away, using breathable renders or coatings, and ventilating interior spaces to reduce condensation.
Rain penetration into penetrating damp or masonry might occur in buildings of all ages. At its most evident, it penetrates right through the wall and is noticeable like a damp patch on the internal wall – often causing flaking/peeling of wallpaper or paintwork and discoloration. Nevertheless, rainwater penetration could be damaging to a property, even if it does not enter all the way through a wall. For instance, increased heat loss, moss growth, and frost damage could be caused by rain penetration into masonry.
Rain penetration is not a problem which is limited to single skin walls. Cavity wall insulation or poorly installed wall-ties can provide a pathway for rain penetration to track through cavity walls.
In many instances, rain penetration is caused by weakly designed or maintained building particulars (for instance; leaking gutters or blocked downpipes) causing large amounts of rainwater for flowing over a small segment of masonry. In these instances, the penetrating damp could generally be healed by correcting the defect.
In other instances, rain penetration could be caused by the brickwork wall not being weather tight enough for withstanding the local weather conditions. Weather tightness of the masonry could be improved by making use of weatherproof paints, cladding, or external render, time and again. Nevertheless these solutions all alter the visual appearance of the masonry.
Penetrating Damp Treatments depends on the kind of damp which is affecting the home. One might also find that they have more than one variety of damp, making the solution more complex. In most instances of damp, one would require consulting a specialist damp company, surveyor or builder.
How to deal with penetrating damp treatments
One would require working out the cause of penetrating damp prior one could treat it. Initiate by examining the gutters and downpipes for cracks or leaks. Check the roof; comprising the flashing, i.e., where the roof meets the chimney wall and painting, i.e., gaps between the tiles. And check the doors and window frames for seeing if there are any gaps.
As one has found where water might be leaking through to the walls, one would perhaps require asking a builder for repairing the fault. The solution depends on how water is seeping in the walls, consequently could comprise repainting the roof or installing new guttering.
