How long a carport lasts is set by its material and its footing, not by its size. Galvanised steel reaches 20 to 25 years in Pretoria; painted mild steel is the outlier that fails early, and shade net cloth is replaced long before the frame under it.
Working life by material
| Structure | Working life in Pretoria | What ends it |
|---|---|---|
| Hot-dip galvanised steel + IBR | 20-25 years | Rust at the post base where water stands |
| Painted mild steel | 8-12 years | Paint fails, then the section rusts from inside |
| Aluminium | 25+ years | Fixings and fasteners, not the frame |
| Timber | 15-20 years, resealed | UV greying and checking if not resealed every 2-3 years |
| Shade net cloth | 10-15 years | UV degrading the knit; the steel frame outlives it |
The post base is where carports actually die
Almost every carport that fails early fails at the same 100 mm: the point where the post meets paving or soil. Water sits there after a Highveld thunderstorm, the coating is thinnest at the cut end, and rust works upward from inside the section where nobody looks. A post set into cast concrete, with the concrete shaped to shed water, on galvanised steel, is the version that reaches twenty years.
This is also the part a kit cannot supply - the footing is decided on site from the ground you actually have. That difference is set out on carport kits vs supplied and installed.
What extends it, cheaply
- Hot-dip galvanising rather than paint over mild steel - the single largest factor.
- Concrete shaped to fall away from the post, so water never stands against it.
- Roof sheets fixed with load-rated fasteners into purlins, not into the sheet alone.
- Flashing where the roof meets a wall, so runoff does not track down the brickwork.
- Re-tensioning fasteners once after the first summer, when the structure has settled.
An aluminium carport skips the rust problem entirely and costs about 1.5 times the steel equivalent; whether that trade is worth it depends on how long you intend to stay.
Specify it to last
Galvanising and footing method are quoted line items, not assumptions - see steel and IBR carports.
Before you build
The rest are on carport questions answered for Pretoria - including whether the structure will hold in a Highveld storm: Will a Carport Blow Away?.
Related detail
How do I tell a carport is failing?
Look at the post bases first - rust blistering at the paving line means the section is going from the inside. Then check for movement at the fixings when the wind gets under the roof, and for rust streaks running down from a fastener, which means the washer has perished.
Can a rusted post be replaced without rebuilding?
Yes, usually. A single post can be propped, cut out and replaced onto a new footing while the rest of the frame stays up. Once several posts have gone at the base it is normally cheaper to rebuild than to keep replacing them.
Whether that lifespan is worth paying for at resale is answered under does a carport add value to a house.
KB Carports builds carports in Pretoria across Tshwane - free on-site measure, and a written quote that states the steel, the footing method and the clearance height.