26 February 2020

Major updates to Upgrading timber joinery doors for fire resistance WIS

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Wood Information Sheet (WIS) Upgrading timber joinery doors for fire resistance has undergone major updates to reflect changes in regulation and include more detail.


The WIS, which gives guidance on assessing the suitability of existing doors for upgrading to give a 20 or 30 minutes' fire resistance comparable with that of purpose-made fire doors, has also undergone a name change (from doorsets to doors) to avoid confusion with the definition as used in harmonised European standards.


The section ‘Strategy to upgrade for fire resistance’ was reviewed following an amendment to BS EN 1634-1:2014+A1:2018 Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware. Fire resistance tests for door and shutter assemblies and open windows. As a result, it has now been updated to show that, depending on the heritage or number of doors, it is not always possible to destructively test the door design that needs upgrading as it would be destroyed in the test. Therefore, an assessment of performance must be made of the existing door and a decision made on its suitability for upgrading by considering its construction against available test evidence.


The WIS has also been updated to include the following guidance.

  • Required fire resistance: in some circumstances, a particularly interesting or valuable doorset may be retained even if the upgrading is only likely to achieve less than 20 or 30 minutes (agreements must be made between conservation and fire officers to add compensatory fire-resisting measures).
  • Assessing heritage doors: What type of features make a door unsuitable for upgrading and what features would require specialist advice.
  • Softwood charring rate of 0.75mm per minute and hardwood charring rate of 0.5mm per minute.
  • Importance of framing in considering the structural performance of the door leaf under fire test conditions and ability to retain the infill panels. Infill panels also need to be considered as they are the weakest part of the door leaf construction.
  • Controlling the spread of smoke with a smoke control seal.
  • Glazing bead, glazing system and fixing detail is critically important and must have test evidence for use with the glass type and must be installed according to manufacturer’s guidance.
  • Frame construction, specification and condition are all aspects of potential fire resistance performance.
  • Depending on lock dimensions, position within the leaf and interruption to the seals, the lock forend, keep and body may require intumescent gasket protection.
  • Depending on the sandwich method, the panel may be considerably thicker than the original panel, which can alter the appearance of the door due to depth of mouldings.
  • Note that replacement restraining hardware will need to be CE marked to comply with the requirements of the CPR.


Members can download a free copy of the WIS Upgrading timber joinery doors for fire resistance. WIS sheets are available to non-members too – purchase a PDF or a hardcopy at the TRADA Bookshop.