The outside walls: windows, render, cladding, paint and the steel in the brickwork
The outside walls keep weather out through a combination of materials and details, and they usually fail at the details: window sills and flashings, sealant joints, render that has cracked or come loose, paint that has stopped protecting timber, and steel lintels or wall ties rusting inside brickwork. Walk each side of the house looking for peeling paint, cracks above windows, stains, soft timber and gaps around frames. Treat paint applied before 1970 as possibly containing lead and fibre-cement made before 1990 as possibly containing asbestos until tested. A horizontal crack with displaced bricks above a window, or regular horizontal cracks in older cavity brick, can mean rusting steel and needs assessment.
- 01OpeningsSills, flashings, frames and the sealant around them
- 02SurfacesRender, cladding and paint that shed the weather
- 03Hidden steelLintels and wall ties that can rust inside brickwork
Fresh paint tells you about the paint, not the wall.
What you'll notice
Walk each side of the house, ideally after rain, and compare the weather side with the sheltered side. These are the signs that matter.
| Sense | Sign | Where to read next |
|---|---|---|
| See | Peeling, blistering or chalky paint, worst on the weather side | Paint and coatings |
| Feel | Soft or spongy timber at window sills, sashes or door frames | Windows and doors |
| See | A horizontal crack above a window or door, with bricks pushed out of line | The steel in the brickwork |
| See | Regular horizontal cracks along mortar joints in older brick walls | Wall ties |
| See | Cracked, bulging or hollow-sounding render | Render |
| See | Hard, cracked or missing sealant around windows and in joints | Sealants and joints |
| See | Stains below windows inside, or water marks down walls outside | Windows and doors |
| Feel | Draughts or rattling around window sashes | Draughts |
Windows and doors
Windows and doors are the most common way water gets into a wall. The frame, the sill below it, the flashing above it and the seal around it all have to work together.
| Type | Where you find it | What to check |
|---|---|---|
| Timber sashes and casements | Older homes, and many renovations | Rot at sills, bottom rails and joints; failed putty or glazing beads; paint condition; sash cords and balances |
| Aluminium | Very common from the 1970s onward | Worn rollers and catches, perished seals, condensation on cold frames, corrosion near the coast |
| uPVC and thermally broken frames | Newer homes and upgrades | Seals, drainage holes kept clear, hardware |
| Door thresholds and frames | All homes | Rot at the base of frames, water entering at sills, gaps under doors |
Look under each window inside for staining or swollen linings, and outside for a sill that falls away from the wall, a drip groove underneath, and a head flashing or weather bar above. Condensation on aluminium frames is common in winter; see condensation.
Render
Render is a coating over brick, block or a board, and it behaves differently depending on what it covers. Cement render on brick can crack with movement and hide earlier cracking. Acrylic texture coatings on lightweight boards rely on sound joints behind them. On older soft brick, hard cement render can trap moisture and push damp higher, as the heritage guide to salt damp explains.
| Sign | What it can mean | Next step |
|---|---|---|
| Fine crazing | Shrinkage of the render surface | Usually cosmetic; recoat |
| Cracks that follow a pattern, such as stepped or from window corners | Movement in the wall behind | Read with the cracks guide |
| Hollow or drummy sound when tapped, or bulging | Render coming away from the wall | Remove and repair loose areas before they fall |
| Damp or salts at the base of a rendered old wall | Render bridging or trapping moisture | See salt damp |
Cladding: fibre-cement, foam and others
Fibre-cement sheets and planks are durable when their joints, edges and penetrations are sealed and painted. Fibre-cement made before 1990 may contain asbestos; the national asbestos agency advises testing before drilling, cutting or sanding. Expanded polystyrene (foam) cladding with a render finish is vulnerable to impact damage and to water getting in at penetrations, joints and the base. YourHome explains how cladding systems manage water behind the finish. For timber boards, see weatherboard homes; for brick, see brick veneer vs double brick.
Sealants and joints
Sealants close the gaps that materials cannot: around window and door frames, at control and articulation joints in brickwork, and at junctions between different materials. They harden, crack and pull away with sun and movement, and when they fail, water reaches the wall behind. Renew sealant that is hard, cracked, shrunken or missing, with a product suited to the joint. Never fill an articulation joint with mortar; see the cracks guide.
Paint and coatings
| Failure | Usual cause | What to do |
|---|---|---|
| Peeling or flaking | Moisture behind the paint, or poor preparation | Find and fix the moisture before repainting |
| Blistering | Moisture or heat under the coating | Check for leaks or damp behind; repaint once dry |
| Chalking | Age and sun breaking down the paint | Clean and recoat; normal ageing |
| Cracking in a crazed pattern | Old, brittle, many-layered paint | Often means a strip back; test for lead first |
| Mould or algae staining | Shade and lasting moisture | Clean, improve drainage and airflow, and recoat |
Paint applied before 1970 may contain lead. The national Lead Alert guide explains how to test and how to work safely; dry sanding, heat-gun stripping and pressure-cleaning old lead paint spread lead dust. Test before any preparation.
The steel in the brickwork: lintels and wall ties
Lintels are the steel angles or beams that carry brickwork over windows and doors. When they rust, the steel expands and lifts the bricks above, causing a horizontal crack along the bottom of the brickwork over the opening, sometimes with the bricks pushed out of line and rust staining. Early repair, by cleaning and treating or replacing the lintel, is far cheaper than rebuilding the brickwork above it.
Wall ties are the small metal ties that join the outer leaf of brick to the frame or inner leaf. They are graded for corrosion resistance under AS 2699.1, from R1 to R4, with R4 for severe exposures such as the coast. Research on Australian walls notes that corrosion is often worst where the tie sits in the mortar, so tie failure is easy to miss until it is advanced (MDPI study). Signs include regular horizontal cracks along mortar joints, bulging or leaning brickwork and cracks at corners. The Australasian Corrosion Association notes that walls with corroded or missing ties performed badly in the 1989 Newcastle earthquake.
Wall-tie and lintel problems need a builder or engineer experienced in masonry repair. Older homes, coastal homes and walls with past damp are the most at risk.
Common misreads
| What people say | What is closer to right |
|---|---|
| "Fresh paint means the walls are sound" | New paint can cover rot, cracks and damp. Look at what the paint is on. |
| "Render protects the brick" | On old soft brick, hard render can trap moisture and make damp worse. |
| "A crack over a window is just settling" | A horizontal crack with displaced bricks above an opening often points to a rusting lintel. |
| "Sealant lasts as long as the building" | Sealants harden and crack with sun and movement; they need periodic renewal. |
| "Sanding old paint is just preparation" | If the paint predates 1970 it may contain lead; test first. |
Worked example: a crack above the front window
Illustrative reasoning example, not an inspected property. A 1960s brick-veneer house near the coast has a horizontal crack running along the bottom of the brickwork above the front window, with a brown stain and two bricks slightly proud of the wall. The window frame inside is fine.
The pattern points to a rusting steel lintel rather than footing movement. The next step is a builder or engineer to expose the end of the lintel, confirm its condition and specify treatment or replacement, with temporary support if needed. Because the house is coastal and of that age, it is worth asking them to check the wall ties at the same time. Record the work in your home record.
Frequently asked questions
What causes a horizontal crack above a window in brickwork?
Often a rusting steel lintel: as the steel corrodes it expands and lifts the brickwork above the opening, causing a horizontal crack, sometimes with displaced bricks and rust staining. A builder or engineer should check it.
What are the signs of wall tie failure?
Regular horizontal cracks along mortar joints, bulging or leaning brickwork and cracks at corners, especially in older or coastal homes. Corrosion is often worst inside the mortar, so it can be advanced before it shows.
Why is my render cracking or sounding hollow?
Fine crazing is usually surface shrinkage. Patterned cracks can reflect movement in the wall behind. A hollow sound or bulging means the render is coming away and should be repaired before it falls.
Why is paint peeling off my exterior walls?
Usually moisture behind the paint or poor preparation. Find and fix the moisture source first; repainting over it will fail again.
Does old exterior paint contain lead?
Paint applied before 1970 may contain lead. Test before sanding, scraping or stripping, and avoid dry sanding, heat guns and pressure-cleaning on old paint.
How often should window sealant be replaced?
When it becomes hard, cracked, shrunken or pulls away from the frame. Sun-exposed and coastal sides usually need it sooner.
Is fibre-cement cladding asbestos?
Fibre-cement made before 1990 may contain asbestos; newer products do not. Only laboratory testing confirms it, so do not drill, cut or sand suspect material.
How this guide was researched
We walk the outside of the house from the signs owners notice, through windows, render, cladding, sealants and paint, to the hidden steel in brickwork, with a fictional example.
Limits: Concealed lintels, ties and cladding junctions need exposure or specialist inspection to confirm. Lead and asbestos need testing.
Sources
- Cladding systemsYourHome, Australian Government · accessed
- Brickwork and blockworkYourHome, Australian Government · accessed
- Lead Alert: the six step guide to painting your homeAustralian Government · accessed
- Asbestos in the homeAsbestos and Silica Safety and Eradication Agency · accessed
- Salt attack and rising damp: a guide to salt damp in historic and older buildingsHeritage agencies of NSW, Victoria and South Australia / Adelaide City Council · accessed
- AS 2699.1:2020 Built-in components for masonry construction, Part 1: Wall tiesStandards Australia · accessed
- Corrosion of wall ties in masonry cavity walls (coastal test sites, WA and NSW)Corrosion and Materials Degradation (MDPI) · accessed
- Corrosion of steel wall ties within brick masonry cavity and veneer wallsAustralasian Corrosion Association · accessed