You open the wardrobe and there is a musty smell, black dots at the back of the cupboard, or shoes with a whitish film. It tends to happen in furniture pushed against an outside wall, especially in winter. This guide explains why, what to do about the furniture and the clothes, and how to tell whether the problem is in the wall. Cleaning mould off the wall itself is in the guide mould on walls, which we do not repeat here.
Updated 3 November 2026. General information, not a substitute for an assessment by a technician or your doctor’s advice.
The essentials
- An outside wall is colder than the others. Behind furniture the air barely moves, and moisture in the air condenses on that cold surface.
- The 2026 English guidance names corners and low points on walls behind sofas or wardrobes as typical places for condensation.
- The Swiss FOPH recommends 10 cm of distance between furniture and outside walls, and says large cabinets should not stand against cold outside walls.
- Moving the furniture does not fix the cause. If the wall is damp, you need to find out why.
- A musty smell with no visible mould can point to hidden mould (FOPH, EPA).
Why mould appears behind and inside furniture
The WHO says the amount of water in materials is the most important factor for fungal growth. A wardrobe against an outside wall combines three things: a cold surface, still air and, often, clothes that are not fully dry or damp shoes.
The FOPH explains that curtains and furniture can hinder air circulation and favour mould. The EPA notes that mould can sit on the back of panelling or wallpaper and on walls behind furniture, where moisture condenses. The English guidance adds everyday moisture sources: showers, cooking and drying laundry indoors.
To understand how condensation works, see condensation in the bedroom and the home.
What you can do about the furniture
| Measure | What the sources say |
|---|---|
| Move the furniture off the outside wall | FOPH: keep 10 cm. English guidance: talk to occupants about “leaving a gap between furniture and external walls”, with no measurement. |
| Do not push large cabinets against cold walls | FOPH: large pieces, such as cabinets filling whole walls, should not stand against cold outside walls. |
| Ventilate the room | FOPH: at least three times a day, with a through-draught, 5 to 10 minutes. |
| Control air humidity | FOPH: 30% to 50% in the heating season, and no more than 40% on very cold days. |
| Do not dry laundry in rooms with problems | FOPH: avoid drying laundry in living spaces with damp problems. |
| Heat | FOPH: in old, poorly insulated buildings, do not delay heating and keep about 20 °C. |
We found other Portuguese pages (press and shop sites) with gaps of 3 to 10 cm, but they are not official and the values differ. So we give only the FOPH figure, the only one from a public body that we read.
A dehumidifier can help lower air humidity, but the FOPH warns not to switch it on before removing visible mould. See dehumidifier: when it helps.
What about clothes, shoes and bags?
We found no page from the DGS, SNS 24 or another health authority explaining how to treat mouldy clothes or footwear. What we can cite:
- The EPA says porous materials with mould may have to be thrown away, because mould grows into the spaces of the material and may be impossible to remove completely.
- The US CDC, in a 2008 advisory on cleaning up after floods, lists “some clothing” and leather among porous items to remove if wet for more than 48 hours and impossible to clean and dry thoroughly. That text is about floods, not wardrobes, so it is only a reference.
- The English guidance says soft furnishings may have to be thrown away if they get mouldy, and that protective clothing used for cleaning should be washed or disposed of.
- The English guidance also warns to take care when disturbing mouldy places, because spores can be released. Use protective equipment.
We cannot say, with a source, which wash temperature or product works on each fabric or on leather. Follow each garment’s label. If someone at home has asthma, allergies or a weakened immune system, ask the family doctor or SNS 24 before handling a lot of mouldy clothing.
When it signals a problem in the wall
A mouldy wardrobe can be just an air and furniture problem. But some signs point to the wall:
- A stain on the wall visible when the furniture is moved, growing or coming back after cleaning.
- The wall feels cold and damp to the touch, even when the room is aired.
- Corners of outside walls repeatedly dark: see thermal bridges and mould in corners.
- A stain low on the wall, with white salt: it may be damp from the ground. See damp walls: the three types.
- Mould with no clear cause in several rooms. The FOPH says that with mould in several rooms, or a smell with no visible mould, investigation is for specialists.
The FOPH adds that if vulnerable people live in the home, mould should not be dealt with by the occupant.
If you rent, tell the landlord in writing, with photos and dates. The FOPH suggests registered post for mould smells. Who pays depends on the cause and the contract: see painting before renting or selling.
What we could not confirm
- An official Portuguese distance between furniture and wall. We found none from the DGS, ADENE or LNEC. The 10 cm figure comes from the FOPH (Switzerland).
- How to wash mouldy clothes, leather and footwear, from an official source. We found none.
- That the wardrobe is the cause. It may just be where the problem shows first.
- How many Portuguese homes have this problem. We found no statistic.
Sources (read on 3 November 2026)
- Swiss Federal Office of Public Health (FOPH), Mould in living spaces, Portuguese version, February 2021 (sections on mould smell, ventilation, air humidity and furnishing).
- Department of Health and Social Care (UK), Understanding and addressing the health risks of damp and mould in the home, updated 1 April 2026 (condensation, ventilation, furniture, fabrics).
- U.S. EPA, A Brief Guide to Mold, Moisture and Your Home (hidden mould) and Mold Cleanup in Your Home (porous materials).
- US CDC, CDC Urges Caution When Cleaning Up Mold, 2008 archive, on post-flood cleaning.
- World Health Organization, WHO guidelines for indoor air quality: dampness and mould, 2009, cited through our guide mould on walls, not re-read today.