Curtain Walling: Resistance to live horizontal loads

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Categories: Performance : Curtain Walling


The curtain wall is required to resist a horizontal live load at sill height. Where a horizontal framing member exists this may be taken as the sill, otherwise the load is applied to a spandrel panel at the appropriate height.

The height of the sill and loads applied should be those in given in EN 1991-1-1.

The revised Product Standard requires that calculations are carried out in accordance with the Eurocode appropriate to the farming material used. In the case of aluminium it is Eurocode 9 (BS EN 1999-1). The Eurocodes apply material factors and check for both:

  • Ultimate Limit State (ULS); A strength check
  • Serviceability Limit State (SLS); A deflection check
  • The current Product Standard requires only a strength check. The revised Product Standard will additionally limit the out of plane deflections of a horizontal framing member to:

  • δ ≤ L/200 if L ≤ 3000 mm
  • δ ≤ 5 mm + L/300 if L > 3000 mm
  • Horizontal live loads should be considered in conjunction with other loads. Guidance on load combinations to be considered is given in CWCT SSBE and CWCT TU14 Load combinations.


    EN1991-1-1Eurocode 1 - Actions on structures - Part 1-1: General actions Densities, selfweights and imposed loads for buildings
    EN1993-1-1Eurocode 3 - Design of steel structures
    EN1995-1-1Eurocode 5 - Design of timber structures
    EN1999-1-1Eurocode 9 - Design of aluminium alloy structures. Part 1-1: General structural rules
    CWCT TU14Load combinations


    Method of test

    There is no method of test; assessment is on the basis of calculation.


    There is no classification for resistance to horizontal live load; a calculated value is declared.

    The current Product Standard requires a resistance value to be declared in kN

    The revised Product Standard requires a deflection to be declared in mm

    CE Marking

    UK Regulations require an overall building air leakage rather than placing a specific requirement on the curtain wall. However, it can be argued that the information is required for the building designer to establish the overall performance of the building. The allowable use of No Performance Determined (npd) is as follows:

    Locationnpd allowed
    England and WalesProbably not
    ScotlandProbably not
    Northern IrelandProbably not