How thick does a blockwork wall need to be for 60-minute fire resistance?

A 100mm dense aggregate blockwork wall (density 1350kg/m3 or above) with 13mm plaster both sides typically achieves 60 minutes fire resistance per BS EN 1996-1-2 Table NA.4. Lightweight aggregate blocks may need to be thicker. Aircrete (AAC) blocks at 100mm also achieve 60 minutes. The mortar must be cement:sand at 1:4 or stronger, and all joints must be fully filled. The plaster coat (gypsum plaster or sand:cement render) contributes to the fire resistance.

Can a single layer of plasterboard achieve 60-minute fire resistance?

Yes, a single layer of 15mm fire-resistant plasterboard (such as Gyproc FireLine) on each side of timber or metal studs with mineral wool insulation in the cavity can achieve 60 minutes fire resistance. This is a tested detail from British Gypsum and other manufacturers. Standard (non-fire-rated) 12.5mm plasterboard typically needs two layers each side for 60 minutes. Always follow the manufacturer tested specification including fixing details and joint treatment.

What fire resistance can a metal stud wall achieve?

Metal stud walls can achieve very high fire resistance ratings depending on the plasterboard specification. Single layer 12.5mm board each side: 30 minutes. Single layer 15mm FireLine each side with mineral wool: 60 minutes. Two layers 15mm FireLine each side: 120 minutes. Three layers 15mm FireLine: up to 240 minutes. Metal studs perform well because steel does not contribute fuel to the fire, though they can lose stiffness at high temperatures.

Does insulation affect wall fire resistance?

Yes, mineral wool insulation within the stud cavity significantly improves fire resistance by slowing heat transfer through the wall. For 60-minute timber stud walls, mineral wool in the cavity is typically required as part of the tested specification. Stone wool or glass wool (non-combustible, Class A1) should be used. Combustible insulation such as PIR or EPS in the cavity would compromise the fire resistance and is not part of any tested fire-rated stud wall detail.

How is fire resistance of walls tested and certified?

Wall fire resistance is tested to BS EN 1364-1 (non-loadbearing) or BS EN 1365-1 (loadbearing) in an accredited furnace test. The wall is exposed to the standard fire curve and assessed for integrity (E — preventing passage of flames and hot gases), insulation (I — temperature rise on unexposed face) and loadbearing capacity (R — structural stability). Manufacturer literature provides tested details. In the absence of test data, tabulated values from BS EN 1996-1-2 (masonry) or BS EN 1992-1-2 (concrete) may be used.

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Fire Resistance Wall Calculator

Determine wall construction specifications to achieve required fire resistance ratings per BS EN and Approved Document B.

Wall Construction Type

Type of wall construction

Target Fire Rating

Required fire resistance period

Wall Height

Floor to ceiling height

Wall Length

Total wall length

How We Calculate This

This calculator determines the wall construction specification needed to achieve a target fire resistance rating, based on construction type, material properties and plasterboard selection.

How it works

Blockwork: Thickness and density determine fire rating per BS EN 1996-1-2.
Stud walls: Plasterboard type and layers determine rating per manufacturer tested details.
Concrete: Thickness and cover determine rating per BS EN 1992-1-2.
Insulation: Mineral wool in cavities improves stud wall performance.