Why north-facing walls fade faster and what to do about it

The north side of a New Zealand house takes the most direct sun through the whole year, and ultraviolet light is what breaks paint down. That is why the north and north-west walls look tired first, while the south wall, which gets far more rain, often still looks reasonable.

It is harsher here than most people assume. NIWA puts the peak UV index in New Zealand at approximately 40 percent greater than at comparable latitudes in the Northern Hemisphere, on account of differences in ozone, sun-earth separation and pollution. Wellington's clean maritime air is pleasant to breathe and hard on paint.

What does the sun actually do to a paint film?

Two separate things, and it helps to know which one you are looking at.

• Pigment breakdown. Ultraviolet attacks the tinters that give the paint its colour. The film stays intact, but the colour drifts, usually lighter and duller.
• Binder breakdown. Ultraviolet also attacks the resin holding the film together. The surface loses sheen, then goes powdery. Run your hand down the wall and it comes away coloured.

Fade is cosmetic. Chalking means the top of the film is being eaten away, and left long enough it stops protecting the timber underneath. On the same house you will often find the north wall chalking while the south wall is still holding its sheen under a layer of grime.

Which colours fade fastest?

It comes down to what the colour is made from. Pale colours are mostly titanium dioxide, an inorganic pigment that is close to unbreakable in sunlight. Strong colours carry a heavy load of tinter, and some tinters are organic compounds that ultraviolet takes apart.

Colour	How it behaves in full sun	What you notice
Whites, creams, pale greys	Very stable colour	Chalking arrives before any fade
Mid greys, beiges, olives, earth tones	Stable, mostly oxide pigments	Slow, even dulling
Deep charcoals and blacks	Colour usually holds	Sheen loss shows badly, surface runs hot
Deep blues and greens	Depends entirely on the tinter used	Gradual shift, some go grey
Strong reds, oranges, bright yellows	The least stable of all	Visible fade first, worst on north and west

This is why a red front door on the north side can go chalky and pink while the grey weatherboards around it still look fine.

Does the sheen level matter?

Yes, a little. A low sheen or satin exterior acrylic holds up better than a dead flat finish, because a flat film carries more pigment and less binder at the surface and starts chalking sooner. Higher sheen also sheds dirt better, which matters on walls the rain does not reach. It is a small effect next to colour choice, but on a hot wall it costs nothing.

How do you choose a colour that will last on the sunny side?

1. Check the colour is actually meant for outside rather than picking it off an interior fandeck. The product data sheet is where that is stated, and the supplier can tell you which colours in a range are the less durable ones in full sun.
2. Test on the wall that gets the sun, not the shaded one. Brush out a sample of at least a square metre on the north wall and look at it in the morning, at midday and in the evening.
3. If you want a strong colour, put it somewhere protected: a door under a porch, a window reveal, a sheltered courtyard wall. Give the north wall the stable colour.
4. Say the trade-off out loud. A deep red house on a north-facing site is a maintenance decision, not a defect. Decide you will recoat that wall sooner and price it in.

Can you repaint just the one wall?

Often yes, and this is where real money gets saved. If the north wall is chalking and the other three are sound, repainting a single elevation is a legitimate job rather than a bodge.

Two things to watch. First, the new paint will not match the old, even out of the same tin, because the old has faded. Break the work at a corner, a downpipe or a change of plane so the difference sits on separate planes and your eye never compares them directly.

Second, the arithmetic on a small job runs differently. Exterior painting sits at roughly $60 to $90 per square metre on our own published 2026 figures, but access does not scale down the same way. If that wall needs scaffolding, the access cost lands on far fewer square metres, so one elevation can look expensive per metre while still being much cheaper than doing the whole house.

Does washing it down actually help?

Washing does not stop ultraviolet. What it does is remove the grit, salt and airborne dirt that sit on the film and grind at it, and on a harbour-edge or south coast property that deposit builds up fast. Fresh water and a soft brush, worked from the top down, is the whole method.

If your paint job came with a workmanship guarantee, read what that document asks of you and ask whoever issued it if the wording is unclear. Maintenance conditions differ between painters and between products, so do not assume yours matches what someone told you about theirs.

Gutter overflow, downpipe splash and shrubs touching the wall all do more damage than fade ever will. Sort those out before you worry about the colour.

When is fade not worth spending money on?

If the film is intact, with no cracking, no lifting and no bare timber showing, and the whole house has dulled evenly, you have an ageing paint job rather than a failing one. You only really notice it when you hold a fresh sample against it. Leave it alone.

Spend the money when the film itself breaks down, which on the north wall happens first and is easy to check: rub it and see whether your hand comes away chalky. If it does, that wall needs work and the others may not. Ask for each elevation to be assessed on its own rather than the house quoted as one number, because on an exterior repaint that difference is the whole conversation.

If you want the sunny side looked at on its own before you commit to a whole-house repaint, get in touch and we will tell you honestly whether it can wait another summer.