Salt staining at skirting

Salt Staining at Skirting

White, fluffy marks low down on a wall are mineral salts left behind by rising damp.

OxfordshireDamp · Remedy · Restore

Field note

Category: Wall symptoms
Likely cause: Rising Damp
Guarantee: 10-year written

CSRT-accredited survey

Schematic · Plate 02

AP/DAMP

White, fluffy marks low down on a wall are mineral salts left behind by rising damp.

The cause

What causes it

White, fluffy or crystalline marks low down on a wall — sometimes called efflorescence — are mineral salts that have been carried up out of the ground by rising damp. As the water travels up the wall and then evaporates at the surface, it leaves the dissolved salts behind. These nitrate and chloride salts are hygroscopic, which means they pull moisture out of the air, so even after the original water source is removed they keep the wall feeling damp until the contaminated plaster is dealt with.

Presentation

What to look for

The deposits typically appear as a powdery white band within the first 30 to 60 cm of the wall, often heaviest at the skirting line. They may feel gritty if you brush them with a finger. Paint over the area tends to bubble or flake, and wallpaper paste fails. In some cases the salts crystallise behind the surface and push the plaster off the wall in patches. The damage is almost always confined to ground-floor walls in contact with the earth.

Why it matters

If it is left alone

The salts themselves are not structurally dangerous, but they are the visible proof that your wall is acting as a wick for ground moisture. Until both the source of the damp and the contaminated plaster are addressed, redecoration will fail repeatedly — fresh paint will lift within months. Salt staining also tends to worsen during humid weather, when the hygroscopic salts pull additional moisture from the air, expanding the visible damage and sometimes triggering secondary mould growth nearby.

The remedy

How we treat it

The fix has two parts. First, the underlying rising damp is treated by installing a chemical damp-proof course at floor level, halting further salt migration. Second, the contaminated plaster is cut back to expose clean substrate and re-rendered with a salt-resistant system that locks the residual contamination behind the new finish. Skirting boards damaged by long-term moisture are replaced. After a short drying period the wall can be redecorated normally and stays sound. Every treatment is covered by our 10-year guarantee and a written specification.

Recommended treatment

Rising Damp Treatment

Every treatment begins with a CSRT-accredited on-site survey, is delivered to a written specification, and is backed by a 10-year guarantee against recurrence.

Written specification 10-year guarantee

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