Structural fire engineering
Structural fire engineering keeps a structure standing long enough for people to escape and firefighters to work. We assess and design the fire performance of the frame, and appraise structures after a fire, across the UK.
What does structural fire engineering actually do?
It shows that the structure will stand for the required period during a fire, so people can escape and firefighters can work. It covers the fire resistance of steel, concrete and timber members and the protection they need, separate from escape routes and compartmentation.
What structural fire engineering covers
Fire safety splits into keeping fire and smoke from spreading and keeping people safe to escape, and the part of protecting the structure itself so it does not collapse during a fire. That structural part is our concern. Every structural material loses strength and stiffness as it heats: steel softens markedly by around 550 degrees, concrete spalls and its reinforcement weakens, and timber chars and loses section. The job is to show the structure retains enough capacity for the required period of fire resistance, whether that is 30, 60, 90 or 120 minutes.
This can be done by the prescriptive route, following the fire resistance periods and tabulated protection in the guidance and Approved Document B, or by a performance-based fire engineering approach using the Eurocode fire parts, BS EN 1991-1-2 for actions and the material fire codes, to demonstrate performance analytically. The performance route often justifies less protection or more open design than the tables allow, which matters on frames, atria and buildings where the prescriptive answer is uneconomic or does not fit the architecture.
Designing fire resistance into the frame
For steel, the usual question is how much protection a member needs to stay below its critical temperature for the required period, which depends on its section factor, the ratio of heated perimeter to mass. A heavy column heats slowly and may need little or no protection; a slender beam heats fast and needs more. We calculate the limiting temperature from the load the member carries in the fire situation, then specify intumescent coating, board or spray to suit, rather than defaulting to a blanket thickness.
Concrete generally performs well in fire because of its mass, and the design centres on cover to the reinforcement and detailing against spalling. Timber is designed by the charring rate: the outer layer chars at a predictable rate and insulates the core, so a member is sized with a sacrificial layer that keeps enough residual section to carry the fire load. Across all three, we check the structure in the fire limit state with the reduced loads and material strengths the Eurocodes specify, because a member only needs to survive the fire, not carry full factored load at the same time.
Post-fire appraisal
After a fire, the question flips: how much strength is left, and can the building be reused. Fire damage is not always what it looks like. Steel that has deformed has lost geometry but, once cooled, largely recovers its strength if it did not reach its critical temperature; steel that reached very high temperatures may need replacement. Concrete tells its history through colour change and spalling, and we assess how deep the damage reaches and whether the reinforcement was affected. Timber retains sound structural core beneath the char, which can often be measured and reused.
We appraise the fire-damaged structure, estimate the temperatures reached from the residual evidence, test where needed, and report what can be retained, what must be repaired and what must be replaced, with calculations to support reinstatement. This supports owners, insurers and building control after a loss. We provide fire engineering and post-fire appraisal across the UK and for European projects, with desktop analysis delivered anywhere and site inspection arranged by region.
What we check.
The points our calculations resolve for a project like this.
- Required fire resistance period and whether a prescriptive or performance route suits
- Steel section factor and limiting temperature, and the protection to match
- Concrete cover, spalling and reinforcement performance in fire
- Timber charring rate and residual section for the fire load
- Checking the structure in the fire limit state with reduced loads to the Eurocodes
- Post-fire assessment of temperatures reached and residual capacity
From enquiry to sign-off.
Enquiry
Send drawings or describe the problem. We confirm the scope, the deliverables and a target timescale.
Information
We agree the survey, drawings or data we need and any site access required.
Engineering
Design, calculation or assessment to the relevant Eurocodes and UK National Annex.
Issue
A clear, defensible report or set of calculations, with assumptions and limitations stated.
Common questions
What does structural fire engineering actually do?
It shows that the structure will stand for the required period during a fire, so people can escape and firefighters can work. It covers the fire resistance of steel, concrete and timber members and the protection they need, separate from escape routes and compartmentation.
What is the difference between the prescriptive and performance approaches?
The prescriptive route follows the tabulated fire resistance periods and protection in the guidance and Approved Document B. The performance-based route uses the Eurocode fire parts to demonstrate the structure analytically, which can justify less protection or more open design where the tables are uneconomic.
How is steel protected against fire?
By keeping it below its critical temperature for the required period. We calculate the limiting temperature from the load and the member's section factor, then specify intumescent coating, board or spray to suit, rather than applying a blanket thickness to every member.
Can a building be reused after a fire?
Often yes, but it must be assessed. We estimate the temperatures reached from the residual evidence, judge how much strength each material retained, and report what can be kept, repaired or replaced, with calculations to support reinstatement for owners and insurers.
Do you provide fire engineering outside Scotland?
Yes. We deliver structural fire engineering and post-fire appraisal across the UK and for European projects. Desktop analysis and calculations are delivered anywhere, with site inspection arranged by region.
Related in structural assessments & specialist services.
Tell us what you are building.
Send the drawings or describe the project. We confirm scope, deliverables and a realistic timescale.
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