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Technical Advisory Document TAD0012
Cladding of FIRETEX FX range coated steelwork
Where it is necessary to clad or box in steelwork which has been previously coated with a FIRETEX FX range material. The recommendation in the past been that there needs to be a gap of 50 times the dry film thickness of the FIRETEX up to a maximum of 50 mm, between the outer surface of the FIRETEX and the inner surface of the cladding, to allow for intumescence to occur in a fire situation.
Recent testing using plasterboard as the cladding material has now indicated that the 50 mm gap is no longer necessary for fire resistance periods up to 60 minutes. The plasterboard can be in direct contact with the FIRETEX. This also applies when using up to 6mm thick fire rated calcium silicate board.
This is dependant on the attachments used to hold the board in place and 1mm thick (approx) angle, attached no wider than 25 mm onto the intumescent on the inner flanges of columns has been found to be satisfactory.
If no additional fixings other than that used to attach the plasterboard to itself is the method of installation, this is also acceptable.
Wooden battens 25 mm wide, either glued or mechanically fixed to the outer flanges can also be used where it is necessary to space the cladding away from the coated column.
When cladding I-Section columns with circular boarding, it is acceptable for the boarding to be in contact with the toes of the I-Section.
This advice is only for fire resistance periods up to 60 minutes on columns.
For fire resistance periods of 90 and 120 minutes on columns, it is necessary to leave a 25 mm gap between the section and the plasterboard.
Due to the many different types of fixings available it is advised that Leighs Paints are consulted prior to carrying out any such installation.
Note that the advice above is our opinion only, based on limited fire testing, and is subject to constant review.
The above assumes that the cladding used is not fire rated in its own right. If the rating required was 60 minutes and a 60 minute board was used as the cladding then intimate contact between the board and the intumescent is always acceptable regardless of the fixing method as the board will provide the fire rating anyway.
Note that if a board is used with a fire rating less than the required fire rating there is no additive effect between the board and the intumescent e.g. 30 minute board plus 30 minute dft of FIRETEX does not give a 60 minute rating and in such a scenario the full 60 minute dft of the FIRETEX must be applied. This same scenario applies to 90 and 120 minute protection also i.e. there is no additive effect.
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