The best temperature to paint indoors is a comfortable, steady room temperature, safely above 10°C and well below 30°C. Farrow & Ball advise against painting below 10°C or above 30°C, Little Greene give 8°C as the minimum for their Intelligent range, and in practice an ordinary heated room is ideal for all three brands we stock.
Temperature matters because water-based paint needs to lose its water at a steady pace and then harden into a continuous film. Too cold and that process slows or stalls; too hot and the paint dries before you have finished laying it off, leaving lap marks and brush marks. Humidity plays its part too.
Photo Credit: Farrow & Ball; Colour Used: Matchstick (2013)
The guidance, brand by brand
These are the limits each brand gives in its own product information:
- Farrow & Ball. Their product advice sheets for Estate Emulsion, Modern Emulsion and Flat Eggshell all say not to paint in temperatures below 10°C or in excessive heat above 30°C.
- Little Greene Intelligent range. Little Greene advise not applying their Intelligent paints when the ambient temperature is below 8°C.
- Little Greene Absolute Matt Emulsion. Its technical data sheet gives a lower minimum of 5°C.
- Paint & Paper Library. Check the guidance on the tin for your chosen finish. Keeping the room above 10°C, as for Farrow & Ball, is a sensible rule.
If you are using more than one brand in the same room, work to the strictest figure: above 10°C and below 30°C covers everything.
When it is too cold
Below the minimum, paint dries slowly and may not form a proper film at all. That can leave a finish that is soft, powdery or uneven in sheen, and more easily marked once you start using the room again. Remember that walls can be colder than the air, particularly external walls and rooms that have been unheated for a while.
- Heat the room first. Put the heating on well before you start so walls and woodwork have warmed through, not just the air.
- Keep it on. Leave the room warm while the paint dries rather than letting it cool overnight.
- Watch for condensation. Little Greene advise that freshly applied paint should not be exposed to heavy condensation before it is completely dry, so avoid painting a cold bathroom straight after a shower.
When it is too hot or humid
In a heatwave, or in direct sun streaming through glass, paint can dry faster than you can work. The edge of each section sets before you join the next, which shows up as lap marks, especially on large walls and in deeper colours.
- Paint in the cooler part of the day. Early morning or evening is better than mid-afternoon in summer.
- Keep the sun off. Draw blinds on sunny windows while you work on that wall.
- Keep a wet edge. Work in manageable sections and finish a whole wall in one go.
Humidity has the opposite effect: damp air slows evaporation. Farrow & Ball note that both temperature and humidity can lengthen drying times, so a steamy kitchen or bathroom needs good ventilation.
Photo Credit: Paint & Paper Library; Colours Used: Bluebird (651), Flat Light (659)
Painting indoors in winter
Winter is a perfectly good time to decorate indoors, and in many ways a good time to choose colour, as we explain in why winter is the best time to paint. With the heating on, most homes sit comfortably within every brand's range.
The balance is between warmth and ventilation. Open a window a little for fresh air, but not so wide that the room drops towards the minimum. If you are painting a radiator, turn it off and let it cool completely first, then leave it off until the paint is dry.
Cold conditions also slow curing, the slow hardening that carries on for days after the paint feels dry. Our guide to painting IKEA furniture covers how to treat freshly painted pieces during that first week.
Questions we are often asked
Can I paint in a garage or outbuilding in winter?
Only if you can keep the space above the minimum while the paint dries. An unheated garage in winter is usually too cold.
Does temperature change the colour?
Not the colour itself, but paint applied in poor conditions can dry with an uneven sheen, which changes how the colour reads.
Should I use a heater to speed things up?
Gentle, even background heat helps. Avoid blasting hot air directly at wet paint, which can make it skin over too quickly.
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