Steel or aluminium windows for a Cape home

Windows have a bigger effect on how a house looks and feels than almost anything else. Slim black steel frames have become hugely popular, while aluminium remains the most common choice in South African homes. Both can be the right answer. Here is how they compare.

Steel windows

Steel is very strong, so steel frames can be extremely slim, giving large areas of glass with fine lines. They suit both period homes, where steel windows were often original, and contemporary designs.

Look: slim sightlines and a crisp, architectural appearance. Hard to imitate convincingly in other materials.
Strength: can span large openings with thin frames.
Cost: generally the most expensive option, especially for custom, heavy-section steel.
Maintenance: steel will rust if the coating is damaged. Frames must be hot-dip galvanised and properly painted or powder-coated, and touched up if scratched. Near the sea, this is critical.
Thermal performance: steel conducts heat. Single-glazed steel windows lose heat in winter and gain it in summer. Thermally improved steel systems exist but cost more.

Aluminium windows

Aluminium is light, does not rust and comes in a wide range of systems, from basic to high-performance.

Look: frames are generally wider than steel, although slim-line aluminium systems now come close.
Cost: wide range, from budget to premium systems.
Maintenance: low. Powder-coated or anodised aluminium needs regular washing, especially near the coast.
Thermal performance: standard aluminium conducts heat, but thermally broken systems separate the inside and outside of the frame and perform much better, especially with double glazing.

Wood and uPVC

Timber windows are traditional in Cape homes and are often required on heritage buildings, but they need regular maintenance. uPVC windows offer good thermal performance at a moderate price but have a chunkier look that does not suit every house.

Cape Town considerations

Wind and rain: Cape Town’s winter storms drive rain against windows. Choose systems rated for the wind loads at your site, with good drainage and seals.
Salt air: on the coast, specify coatings and hardware for marine environments (see our guide on building near the sea).
Energy rules: the national energy-efficiency regulations limit how much glazing you can have without performance glass. Large glazed areas often require double glazing or high-performance glass to comply.
Heritage areas: the heritage authority may require timber or steel to match the original windows.

Our experience

At Picardi in Constantia, floor-to-ceiling steel-framed windows were central to the renovation. They bring light deep into the living areas and frame the mountain. On other projects, thermally broken aluminium has been the better choice for the budget and the location.

The right answer depends on the house, the site, the budget and how much maintenance you want. If you are deciding, talk to us before you order.