Wind-driven rain and why Wellington paint fails from the edges in

Wellington rain does not fall onto a wall, it is pushed into it. At gale strength water is forced into every joint, board lap, cut end and gap in the paint film, which is why paint here fails at board ends, window reveals and the bottom edge of boards while the middle of the same board is still perfectly sound.

That pattern tells you what you are dealing with. Failure that starts at edges and creeps inward is water getting behind the film. Failure spread evenly across a whole face is sunlight and age, and that is a far cheaper problem.

Why do the edges go first?

Timber drinks through its end grain many times faster than through its face. A weatherboard that has been primed and given two coats is still a piece of timber with two sawn ends, and those ends sit at every scarf joint, every corner, every scriber and every opening.

Wind-driven rain finds them. Water goes in, the board swells, the paint film on the outside is pushed off from behind rather than worn off from the front, and the failure then travels back along the board from the end. That is why a blister at a board end has clean bare timber under it, while a blister caused by heat has a chalky, weathered surface underneath.

Where on the house does it land hardest?

Not evenly. Wind pressure concentrates at the corners of a building and along the top of a wall under the eaves line, so those are the areas that take the most driven water. Add the windward gable, which usually has no eave protecting it at all, and the band of cladding just above a deck, where rain bounces straight back up into the boards.

Where you see it	What it looks like	What is causing it	What it needs
Board ends at corners and joints	Flaking back from the end, bare timber underneath	End grain drawing water in	Scrape back, dry out, seal the end, prime, recoat
Bottom lip of weatherboards	Thin ragged line of lifted paint along the lower edge	Water tracking along the lap and sitting on the edge	Sand back, prime the edge properly, two coats
Window and door reveals	Blistering and dark staining on the reveal and sill	Driven rain plus a flashing that is not shedding	Check the flashing first, then repair the coating
Windward gable end	Whole boards failing while the sheltered gable is fine	No eave overhang, full exposure	Heavier preparation on that elevation alone
The band just above a deck	Peeling in a band at deck level, sometimes soft timber	Rain splashback and poor drying	Clearance and drainage fixed before any repainting
Even fade across a whole wall	Chalky, faded, no lifting	Ultraviolet light and normal age	Wash and recoat, no stripping needed

Does another coat fix it?

No, and it usually makes it worse. Painting over a wall that is taking water behind the film seals the escape route. Timber that cannot dry outward stays wet, and wet timber is where rot starts, so a cosmetic fix at year one can become a board replacement at year four.

The order has to be: find where the water is entering, stop that, let the timber dry, then coat it. A moisture meter reading before the first coat goes on is worth more than an extra coat afterwards.

Where does caulk help, and where does it trap water?

Sealant belongs in vertical joints, around joinery, at the tops of scribers and where corner boxing meets the cladding. Those are places water enters and cannot easily drain.

It does not belong under the lap of a weatherboard. That gap is a drainage and drying path, and sealing it turns the wall cavity into a container. It is the most common well-meant mistake on Wellington weatherboard houses, and it is usually done by someone trying to stop exactly the problem it causes.

What actually stops it?

• Seal every cut end. When a board is trimmed on site, that end gets primer before it goes up, not after.
• Back-prime replacement boards, including the ends, before installing them.
• Prime bare timber the same day it is exposed. Timber left bare overnight in Wellington takes on moisture you then paint in.
• Maintain the film at the ends and edges rather than the middle. Those edges are where the next repaint is decided.
• Check the boring things: head flashings over openings, gutter falls, downpipe discharge, and whether a deck is butted hard against the cladding.

Can you repair only the affected areas?

Yes, and often you should. If the rest of the coating is sound and the colour has not shifted too far, cutting out and repairing the failed edges is legitimate work, not a bodge. It buys years on a wall that does not otherwise need anything.

It stops being sensible when more than roughly a quarter of an elevation is involved, when the colour will not blend because the surrounding paint has faded, or when the patches are all over the house rather than in one exposed band. At that point you are paying for setup and access twice, and a full exterior repaint of that elevation is cheaper per square metre.

Is it always the paint's fault?

Frequently not. Before anyone quotes to repaint, rule out a blocked gutter overflowing behind the fascia, a failed or missing head flashing above a window, a downpipe discharging at the base of a wall, a deck or garden bed sitting above the bottom of the cladding, and a sprinkler that has been pointed at the house for three summers.

All of those produce failure that looks exactly like weather damage and none of them are fixed by paint. A painter who checks those before quoting is saving you the cost of doing the job twice.

If your paint is lifting at the edges and you want to know whether it is a repair or a repaint, get in touch and we will take a look before anyone quotes a number.