Protection
Fire Protection for Pre-Engineered Steel Buildings
Fire protection for a steel building is the set of measures, from passive protection such as intumescent coatings, boards and fire-rated walls to active systems such as sprinklers, used to meet the life-safety and property-protection requirements of the building code and the authority having jurisdiction.
Key facts
- Fire requirements come from the local building code and depend on occupancy, area, height and separation distances.
- Many single-story industrial and storage buildings need no fire resistance rating for the structural frame.
- Where ratings apply, protection is provided by tested systems such as intumescent coatings, sprayed materials or boards.
- Sprinklers, compartmentation and fire separation distance often reduce the passive protection needed.
- Insulation and panel cores should be selected with their reaction-to-fire classification in mind.
How building codes set fire requirements
Fire requirements are set by the governing building code, for example the IBC in the United States, the NBCC in Canada or the national code in Australia and Europe, together with any local amendments. The code considers occupancy type, floor area, number of stories, distance to property lines and whether the building is sprinklered.
The outcome is a set of requirements for structural fire resistance, fire-rated walls, exit routes, smoke control and active systems. These requirements are confirmed by the architect, fire engineer and authority having jurisdiction early in the project, because they affect layout, materials and cost.
When the steel frame needs a fire resistance rating
A large share of single-story pre-engineered buildings, such as warehouses, workshops and agricultural buildings, are permitted by code to have an unprotected steel frame when area limits, separation distances or sprinkler provisions are met. Steel is noncombustible, and in these cases life safety is achieved mainly through exits, detection and compartment size.
Ratings are more likely to be required for multi-story office blocks, mezzanines used for occupancy, buildings close to a boundary, and high-hazard storage. In those cases the elements to be rated, and the rating period, are defined by the design team rather than assumed.
Passive protection methods for steel members
Intumescent coatings expand when heated to form an insulating char, and they suit exposed steel where appearance matters. Sprayed fire-resistive materials are economical for concealed members. Board systems encase columns and beams and are often used where a clean, durable finish is wanted.
Each method must be applied as part of a tested and listed system for the section shape and size involved. Tapered, slender built-up members may need more material than heavier rolled sections, so the protection designer needs the actual member sizes from the PEB engineering drawings.
Fire walls, separations and the metal building envelope
Fire-rated walls between occupancies or along a boundary are commonly built in masonry, precast concrete or rated panel systems. Where a rated wall meets a light steel frame, the connection must allow the frame on the fire side to deform or collapse without pulling the wall down, and this is a detail that needs coordination between the PEB engineer and the wall designer.
Envelope materials matter too. Insulated sandwich panels with mineral wool cores, and insulation with suitable reaction-to-fire classification, help limit fire spread. The panel core and facing should be selected with the code requirements and insurer guidance in hand.
Active systems and their effect on the structure
Sprinkler systems are often required for large storage buildings and they can reduce passive protection needs. Sprinkler mains, branch lines and in-rack systems add load to the roof structure, so the expected sprinkler load should be included in the collateral load given to the PEB designer.
Smoke vents, roof hatches and detection systems also need framed openings and support. Planning them at the design stage avoids cutting purlins later, which can weaken the roof.
Points to confirm with your fire engineer
- Occupancy classification and governing building code edition.
- Whether any structural elements require a fire resistance rating.
- Location and rating of fire walls and separations.
- Sprinkler type and the collateral load it adds to the roof.
- Reaction-to-fire class required for insulation and panel cores.
- Tested system and member sizes for any passive protection.
Frequently Asked Questions
Does a steel warehouse need fireproofing?
Often it does not. Many codes permit unprotected steel frames in single-story storage and industrial buildings that meet area, separation and sprinkler conditions. The answer depends on the code, occupancy and site, so it is confirmed by the fire engineer and authority having jurisdiction.
Can intumescent paint be applied to tapered PEB frames?
Yes, provided the product is used as a tested system suitable for the section type and the thickness is determined from the actual member dimensions. Built-up members with thin webs can require more coating, so early coordination helps control cost.
Do sprinklers affect the steel design?
Yes. Pipework and hangers add load to purlins and frames. The sprinkler load should be included in the collateral load allowance so the roof structure is designed for it.
Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.
