Technical Support - Keystone Lintels

Standard Keystone Lintel

All Keystone standard steel lintels satisfy the Thermal Performance requirements of England and Wales’s Part L of the building regulations, Northern Ireland’s Part F and Scotland’s Technical Handbook, section 6. Our standard S/K range has Psi values ranging from 0.2 to 0.3 W/m.k. The exact figure of your Psi value depends upon the wall construction the lintel is built in to. For more detailed information on Psi values applicable to your wall construction or for more information on accredited construction details please contact Keystone’s technical team.

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Structural Performance

The Keystone lintel range has safe working loads as detailed in each applicable loading table. The structural performance figures within each table have been ascertained by testing in accordance with the requirements of BS 5977 Part 2 1983 and BS EN 845-2:2003. The figures take into account the different loading arrangements which are common to traditional cavity wall construction.

Differential Load Ratio 3:1
Up to 75% loading on the inner leaf.
Differential Load Ratio 19:1
Up to 95% loading on the inner leaf.

How to interpret load tables and select the correct lintel

For detailed information on how to interpret our load tables and select a lintel, please see our Products page.

Corrosion Resistance

Keystone lintels are manufactured from high quality grade pre-galvanised mild steel with a zinc coating of 600 g/m² (including both sides). The “hot dipped, pre-galvanising” process is carried out at the mill to ensure a more consistent quality of zinc coating. This guarantees a more effective anti-corrosive system. Furthermore pre-galvanised lintels are much more “environmentally friendly” than post galvanised lintels.

Lintel Life Span

The Keystone lintel range complies with the technical requirements of the BLP (Building Life Plans) regarding the durability data of mild steel, cold formed lintels. The service life of Keystone lintels, when installed with a flexible DPC, will be the same as that anticipated for the building.

Fire Testing

A Keystone lintel has been subjected to a fire test (ref: WARRES No. 101263) in accordance with BS 476:Part20: 1987, at Exova Warringtonfire and achieved a one hour fire performance. If longer fire rating figures are required they can be achieved by applying a proprietary fire board to the soffit of the inner flange of the steel lintels. Please contact our technical team if further fire rating provisions are required.

Lintel Load Tables

For full details of load tables specific to your lintel type please see our steel lintels page.

Hi-therm Lintel

Keystone’s Hi-therm Lintel is a combination of Glass Reinforced Plastic (GRP) and Galvanised Steel. When combined these two materials form the ultimate in lintel design – Psi 0.05 W/m.K

Testing of Keystone’s Hi-therm Lintel was carried out by the BRE (Building Research Establishment) using Physibel’s thermal analysis software TRISCO which complies with BS EN ISO 10211-1. The modelling follows the requirements of the BRE conventions document BR497.

Psi Comparison Chart

To help understand the immense thermal benefits of the Hi-therm Lintel it must be compared to other lintel types.

Lintel Type Comparison Values
Keystone Hi-therm Lintel 0.05 W/m.k
Typical Keystone Lintel 0.23 W/m.K
Non-plated Steel Lintel (default) 0.3 W/m.K
Plated Steel Lintel (default) 0.5 W/m.K

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Outstanding Advantages

  • Outperforms all other cavity wall lintels for Thermal Performance. GRP has very low thermal conductivity which practically eliminates cold bridging.

  • Outperforms Stainless steel and Galvanised steel for corrosion resistance. The GRP outer flange, quite simply, will never corrode.

  • Outperforms stainless steel in price. GRP is more competitively priced than stainless steel.

  • DPC is not required. The GRP outer flange does not require the installation of a Damp Proof Course/ Cavity Tray.

Building regulations require that lintels should be assessed for their effect on the thermal performance of a building. A lintels thermal performance is expressed in terms of Psi Values (ψ) i.e. linear thermal transmittance.

Thermal Performance

Building regulations require that steel lintels should be assessed for their effect on the thermal performance of a building. The thermal performance of a lintel is expressed in terms of Psi Values (ψ) i.e. linear thermal transmittance.