Dampness: capillarity, filtration, condensation and breaks

Dampness is the most common pathology in buildings. Although at first glance they may seem like an aesthetic problem, they almost always reveal a construction or maintenance fault that, if not correctly identified, tends to reappear after superficial repairs. This article describes the four main origins of damp and what implications they have from an expert point of view.

Capillary humidity

It occurs when water from the ground rises up the walls through the pores of the material, generally due to lack or deterioration of the moisture barrier. Its typical symptoms:

• Stains in the lower part of the wall, up to a certain constant height.
• White salt efflorescence on the surface.
• Deterioration of skirting boards, paints and coatings.

In modern construction, capillarity indicates a failure of execution in the perimeter waterproofing or in the horizontal barrier.

Moisture through filtration

It appears when water penetrates from the outside, whether through a roof, façade, terrace, patios or defective joints. The usual signs are:

• Spots concentrated in areas close to the focus.
• Appearance or aggravation with intense rain.
• Deterioration located in false ceilings, floor joints or corners.

The origin is usually in poorly executed waterproofing sheets, aged joints, non-existent expansion joints or poor finishes.

Condensation humidity

It is due to the temperature difference between the humid interior air and cold surfaces of the enclosure, usually thermal bridges. Typical signs:

• Black mold stains in corners, blind boxes and joints with flooring.
• Concentration in bedrooms and rooms with poor ventilation.
• Seasonal appearance, more marked in winter.

The cause is usually insufficient or poorly executed thermal insulation and, in many cases, inadequate ventilation.

Moisture due to installation breakage

Corresponds to plumbing, sanitation or heating leaks. It can be punctual and localized or silent and progressive. The signs:

• Spots that appear and spread unrelated to rain.
• Unexplained increase in water consumption.
• Deformation of pavements or false ceilings.

How to technically accredit

The expert uses a combination of visual inspection, humidity measurement, thermography and, where appropriate, exploratory openings. Distinguishing the origin is essential: without a correct diagnosis, any repair fails.

Related links

For the specific tools used, see the article on technical testing. If the problem affects a recently delivered home, also review the section on ten-year, three-year and annual guarantee. to commission a report, go to Contact or the specialty of Defective workmanship.