You can paint in humid conditions, but moisture in the air slows everything down. Water-based paint dries as its water evaporates, and in damp, still air that happens far more slowly, so each coat stays soft for longer and takes longer to harden. Farrow & Ball advise applying their paints only when the relative humidity is below 80%, and both they and Little Greene warn that condensation on paint that has not fully cured can leave lasting marks. Ventilate well, allow longer between coats and keep steam away for the first days.
Humidity is most often a problem in bathrooms, kitchens and utility rooms, during damp spells of autumn weather, and on outside work early in the morning. It is rarely a reason to cancel a project, but it is a reason to plan it properly.
Photo Credit: Little Greene; Colour Used: Hicks' Blue (208)
Why humidity affects paint
Farrow & Ball note that cooler or more humid conditions lengthen drying times, and that darker colours can take longer still. Touch dry is also not the same as cured: a coat can feel dry within an hour or two and still be soft underneath for days. Most of the problems below happen in that window.
- Slow drying and curing. The longer a coat stays wet, the longer it is vulnerable to knocks, dust and moisture, and the longer you must wait before the next coat.
- Marks from condensation. Farrow & Ball advise extra care in kitchens, bathrooms and other humid areas, because changes in temperature cause condensation, which may lead to surface defects if the paint is not fully cured. Little Greene state that Intelligent Matt Emulsion should not be exposed to heavy surface condensation before it is completely dry, as this can cause permanent marking.
- Surfactant leaching. Water-based paints contain surfactants, ingredients that help them flow and apply evenly. When fresh paint is slow to dry, Sherwin-Williams explain, these water-soluble ingredients can collect on the surface as tan, brown or clear patches that feel shiny, soapy or sticky. Bathroom ceilings are the classic place to see it.
- Poor adhesion. Paint needs a clean, dry surface to grip. Moisture trapped between the wall and the first coat weakens the bond, which can show up later as flaking or blistering.
- Mould. Damp rooms encourage mould, and painting over it does not solve it. Farrow & Ball specify that surfaces must be clean and free from contamination such as dirt, grease and mould before painting.
Check the conditions before you start
An inexpensive thermometer and hygrometer takes the guesswork out of it.
- Humidity: Farrow & Ball specify application below 80% relative humidity.
- Temperature: Farrow & Ball advise not painting below 10°C or above 30°C. Little Greene's Intelligent paints should be applied at 8°C or above.
- The surface: walls must be dry to the touch and free of condensation. A bathroom straight after a morning shower, or a kitchen with pans on the hob, is not the moment to start.
Outside, avoid early mornings when dew is still on the surface, and do not paint if rain or fog is likely before the paint has had time to dry.
Photo Credit: Little Greene; Colours Used: Royal Navy (257), Bassoon (336)
How to paint a humid room, step by step
- Deal with any mould first. Treat it, clean the wall and let it dry thoroughly before you open the tin.
- Pick a quiet day. Paint when the room will not be used for showers, baths or cooking for as long as possible afterwards.
- Air the room and dry the walls. Open windows and doors, run the extractor and wipe down any condensation. A dehumidifier in a closed room is the most effective way to bring humidity down quickly. Gentle background heating helps too, but avoid blasting heat at wet paint.
- Keep coats thin. Two thin, even coats dry far better than one heavy one, which can stay soft underneath.
- Respect the recoat time, then add to it. Farrow & Ball recommend at least four hours between coats of Modern Emulsion and Modern Eggshell, and Little Greene's Intelligent paints can be recoated in one to four hours. In damp conditions, allow the longer end and check the first coat is properly dry before going again.
- Keep steam away and keep ventilating. Avoid showers, baths, boiling pans and tumble dryers in the room for as long as you reasonably can, ideally several days. Little Greene advise keeping the home well ventilated during activities such as cooking, so for the first week or two use the extractor and open a window after every shower.
Patience matters more than anything else here. Farrow & Ball recommend leaving at least 14 days before cleaning Modern Emulsion, and say some darker colours take up to 14 days to reach full hardness. Little Greene's Intelligent finishes take up to seven days to cure fully.
Photo Credit: Little Greene; Colour Used: Giallo (337)
Choosing a finish for bathrooms and kitchens
All three of the brands we stock make a finish designed for damp, busy rooms. The softest, chalkiest finishes are better kept for bedrooms and sitting rooms.
- Farrow & Ball. Modern Emulsion (7% sheen) is their washable matt, which they describe as especially suited to kitchens and bathrooms. It contains preservatives to protect against mould, though it is not for shower enclosures or surfaces in direct contact with water. For woodwork, Modern Eggshell (40%) suits skirtings, doors and bath panels. Their Estate Emulsion is a beautiful chalky finish, but Farrow & Ball list kitchens and bathrooms among the areas to avoid.
- Little Greene. For bathrooms, Little Greene recommend Intelligent Eggshell, which they say is formulated to resist moisture, staining and general wear, and is especially suited to rooms with limited extraction or condensation. Intelligent Matt Emulsion (2%) is their tough, washable matt for a flatter look, and for kitchen cabinets they suggest Intelligent Satin.
- Paint & Paper Library. Architects' Matt is suitable for kitchen and bathroom walls and ceilings, and Architects' Eggshell is recommended for kitchen and bathroom walls, particularly where condensation is a concern.
If you love a particular colour, it can usually be mixed in the tougher finish, so there is no need to compromise on the shade itself. Our Spring Bathroom Edit has a few ideas to start from, and ordering a sample pot lets you see it in the room first.
Photo Credit: Farrow & Ball; Colour Used: Purbeck Stone (275)
Questions we are often asked
Can I paint a bathroom and shower the same day?
It is best not to. Steam on paint that has not cured can mark it. Leave the room to dry for as long as you can, and ventilate well when you do first use it.
What are the brown, sticky streaks on my new bathroom ceiling?
Most likely surfactant leaching, caused by moisture reaching the paint before it dried. Sherwin-Williams advise washing the area with soap and water and rinsing, noting that it may reappear once or twice before it has gone, and removing as much as possible before any repainting.
Can I use a matt paint in a bathroom?
Yes, as long as it is a matt made for it, such as Modern Emulsion, Intelligent Matt Emulsion or Architects' Matt. Where there is a lot of condensation, an eggshell is the safer choice. None of these is meant for inside a shower, which is better tiled or panelled.
