Why 2000s Hardie-clad homes fail at the joins first

The short answer: the boards hold, the gaps between them move

Hardie boards are made to stay stable, so the joins carry the movement. James Hardie says its fibre cement offers dimensional stability, resisting swelling, movement and warping. So on a house built in the 2000s, the middle of a board is rarely where paint gives up first.

The joins are made differently. In James Hardie's current Australian cladding spec, weatherboards and planks are fixed with a 3mm gap at the butt joints, ready to take sealant. Sheets are often jointed with PVC jointers. Corners get their own flashings or trims. Each of those is a line where two parts meet, and two parts never move quite as one.

Dulux explains why that matters. Hotter surfaces make the wall expand and contract more, which puts more stress on the paint. As paint ages it gets less flexible and less able to cope with that constant movement. The result can be cracking, flaking, peeling or blistering. So on the 2000s houses we look at, the first cracks tend to line up with the joins. That's where the wall flexes most.

Where to look: the joins that go first

Most Hardie-clad homes have the same handful of joins. Here's what each one is, based on James Hardie's cladding spec, and what to look for when you walk around the house.

There's one more spot we check on every Forest Glen house. Where a painted fascia meets a Colorbond roof line, the two materials move at different rates, and the paint at that line often goes before the walls do. Sun matters too. West-facing walls fade well ahead of the rest of the house, and north walls get plenty of sun as well.

Why heat, age and dark colours speed it up

Dark colours put the joins under more strain. Dulux says deep colours soak up more heat than light ones, and a hotter wall expands and contracts more. That adds stress to the paint and to the material under it. Deep colours also tend to reach their first maintenance sooner than lighter ones.

James Hardie's spec sets a limit on dark paint for one part of the wall. When PVC accessories such as jointers get painted, the paint must have a light reflectance value (LRV) above 40 percent. In plain words, the colour on those parts can't be too dark. That ties back to the heat point above, since Dulux says darker colours soak up more heat. Some building materials set a minimum LRV like this, and Dulux warns that going under it can void the maker's warranty.

Dirt and salt are the other half of it. Dulux says paint struggles to grip a surface with dirt, mould, salt or any loose or powdery layer on it, and that even a high quality paint can fail on a dirty surface. That's why a proper wash comes before anything else on our jobs. If you're choosing a new colour, our guide to exterior house colours covers how colour and sun work together.

A ten-minute check you can do from the ground

You can tell a lot about your cladding without a ladder. Pick a dry day and work around the house in this order.

1. Start on the west and north walls. They get the most sun, so they show trouble first.
2. Look along each butt joint. A straight hairline crack running up the join, or sealant that has shrunk or come away from a board end, means water can get in.
3. Check under every window. Staining or bubbles under a window head or sill point to water getting in behind the paint.
4. Rub the wall with a dry hand. Powder on your palm is chalking. It has to be washed off before any new paint will stick.
5. Do the tape test. Dulux's test for old paint is to cut a small X with a sharp knife, press about 10cm of tape firmly across it, then pull it off fast. If paint comes away on the tape, the loose paint has to come off before a new coat goes on.
6. Stop at shoulder height. Note anything you can see higher up, but leave second-storey walls and eaves to a painter with proper access gear.

Before anyone sands, check the build year. The QBCC says asbestos was banned in building products in 1990, but some houses built in the 1990s or early 2000s still used products with asbestos in them until a total ban in 2003. If you aren't sure what's on your walls, have it tested by a qualified professional before any sanding or cutting. We're qualified to test for asbestos and we test first.

Fixing the joins: reseal first, then paint

A failed join gets fixed before any paint goes on, or the new coat cracks along the same line. The order we work in on a full exterior is wash, scrape, sand, fill, seal, undercoat, then the topcoat system that wall needs. On a Hardie-clad house the sealing step is where the joins get reworked.

James Hardie's spec gives a few rules for the sealant itself. Don't mix sealant types in a joint. Hardie recommends its own polyurethane joint sealant, which it describes as paintable and exterior grade. The sealant has to fill the gap fully and bond to both board edges, with the excess wiped off. Joins sitting right over a stud hold up better, because Hardie says the sealant there is more resistant to cracking and failure.

Then the paint. James Hardie tells you to ask the paint maker which paint systems suit fibre cement. Dulux's fix for peeling is to find and stop the water first. Then scrape off all loose paint, sand rough spots and repaint with a top quality water-based exterior paint. Dulux lists Weathershield as suitable for fibre cement, and it's one of the two systems we use on most exteriors.

A newer house often doesn't need the whole lot done. If the boards are sound and only the joins and the sunny walls have gone, targeted work can carry the house a few more years, and we'll tell you if that's the case. For what a full job involves, see our exterior house painting service.

Forest Glen, Sippy Downs and Aura: what this means locally

Forest Glen is where this guide matters most. Most of its homes went up from the 2000s with Hardie cladding and Colorbond roofs, so many are now around 20 years old, and the joins are where we start. Our page on exterior painting in Forest Glen covers how we survey the junctions there before we price the walls.

The same checks apply to any fibre cement home in the newer estates. That includes the family estates around Sippy Downs and the new-build streets of Aura. On a brand new house, James Hardie's spec says external cladding must be painted within 90 days of installation, which is worth knowing if you're adding an extension. We work right across the Sunshine Coast, with a free quote usually inside a business day.