How to know if the humidity in your house is due to condensation, filtration or capillarity

The stain you see on the wall does not always have the same origin, and making a mistake when it comes to treating it can make the problem worse and make the repair more expensive. Below you will learn how to differentiate the three most frequent sources of damp and how to choose the right solution before painting or waterproofing.

Types of humidity you may encounter

Condensation dampness

This forms when indoor water vapour cools on cold surfaces (windows, corners of poorly insulated rooms). You will notice constant misting on windows, dark mould on bathroom joints and warped paint on the top of walls.

Dampness from seepage

Water from rain or other external sources seeps in through cracks in the façade, roofs or poorly sealed joints. Irregular stains appear and grow on rainy days, and saltpetre flakes off the paint around windows or ceilings.

Moisture from rising damp

Water from the ground slowly rises through the pores of the wall, typical in dwellings without a damp-proof barrier. You will see a horizontal ridge between 30 and 80 cm from the ground, dusty flaking and a cold sensation when resting your hand on the lower part of the wall.

Diagnosing the origin step by step

Observe the shape and height of the stain.

• Rounded, raised stains are usually condensation.

• Stains arising from a crack point to seepage.

• Continuous line from the baseboard is a sign of capillary action.

Carry out the plastic test

Stick clear plastic over the area and seal the edges for 48 hours:

• Drops on inner face → vapour inside → condensation.

• Drops on the outer face → water penetrates the wall → seepage or capillarity.

Measure ventilation and relative humidity

If the hygrometer reads more than 60 % and there is hardly any ventilation, condensation is the main cause.

Why dampness should be tackled as soon as possible

The WHO reminds us that prolonged exposure to mould and damp environments increases the risk of asthma and respiratory diseases (WHO Guidelines for Indoor Air Quality: Dampness and Mould). In addition, plaster disintegrates, paint falls off and the wall loses its insulating capacity, increasing your heating or air-conditioning consumption.

Professional solutions according to the type of humidity

Condensation

• Increase natural ventilation or install mechanical ventilation.

• Insulate the coldest thermal bridges.

• Apply anti-condensation and anti-mould paints that allow vapour to escape without fungus appearing.

Filtration

• Seal cracks with elastic mastics.

• Waterproof façades or roofs with resins and asphalt fabrics.

• Protect the finish with a waterproof façade coating resistant to rain and solar radiation.

Capillarity

• Inject resins that create a chemical damp-proof barrier.

• Replace deteriorated plasters with macroporous mortars that allow moisture to evaporate.

• Finish with breathable mineral paints applied by our team of house painters to prevent future buckling.

When to ask for professional help

• Stains reappear soon after cleaning.

• Plaster crumbles and saltpetre covers skirting boards.

• There are doubts between two types of dampness or several appear at the same time.

In these situations a technical diagnosis is advisable. At Bartolomé Bas Pinturas we evaluate the home, locate the exact cause and propose the construction, waterproofing and painting treatment that will give your walls a healthy and lasting appearance. Contact us and forget about damp!