Steel loses 60% of its strength at 550°C — well within a typical building fire. South African building regs require 30, 60, 90, or 120 minutes of protection depending on building type and height. The choice of protection method has aesthetic, programme, and cost implications.
How long is required
- Domestic up to 5m above ground: 30 minutes
- Domestic above 5m: 60 minutes
- Office under 18m: 60 minutes
- Office over 30m: 90+ minutes
- Industrial: depends on use, often 30–60 minutes
- Car parks (open-sided): often unprotected
Intumescent paint
Paint that swells when heated, forming an insulating char layer.
- Thickness: 0.5–4mm depending on protection level
- Cost: R500–R1,400 per m² installed
- Pros: Steel remains visible, thin coating, applies on site or off-site
- Cons: Requires careful surface preparation, decorative coating after, more expensive per m² than board
Standard for architectural steel where the structure is exposed.
Board encasement
Calcium silicate, gypsum, or vermiculite boards fixed around the steel section.
- Cost: R360–R900 per m² installed
- Pros: Lower cost, robust impact resistance, no painting needed
- Cons: Bulkier than paint, joints need detailing, hides the steel
Standard for concealed steel where appearance doesn't matter.
Cementitious spray
Sprayed-on cementitious or gypsum-based coating.
- Cost: R300–R700 per m² installed
- Pros: Fast application, lowest cost
- Cons: Rough appearance (concealed only), wet trade, overspray issues
Common in industrial and concealed commercial applications.
Concrete encasement
Steel cast within concrete column or beam. Traditional, most robust, adds structural capacity.
- Cost: R1,100–R2,600 per m² of steel surface
- Pros: Highly durable, no maintenance, fire rating effectively unlimited
- Cons: Heavy, slow, increases column dimensions significantly
Choice matrix
- Exposed architectural steel → intumescent paint
- Concealed steel in walls/ceilings → board encasement
- Industrial, concealed → cementitious spray
- Highest durability or composite design → concrete encasement
MCFAR specifies fire protection across all structural projects.
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Request a QuoteFrequently Asked Questions
Can I leave structural steel unprotected?
Only in specific situations (open-sided car parks, agricultural buildings, certain industrial). Most habitable structures require protection.
Does intumescent paint need re-applying?
No, but it must remain undamaged. Inspect every few years and patch any damage.