In July 2013 the new Posi-Joist flooring system, Posi-Joist FireSafe received formal approval from the UKTFA, the Health & Safety Executive and the Health & Safety Laboratory. Posi-Joist FireSafe and FireSafe Plus have now been accepted as providing the robustness required as a floor to go into a Category C timber frame construction.
Available now from Posi-Joist manufacturers, Posi-Joist FireSafe will be included in the next edition of UKTFA Product Paper 4, expected in late September 2013, where it will be detailed as achieving the “2 points” required for use in a Category C construction.
Posi-Joist FireSafe combines timber chords which are treated with an approved FR build flame retardant with MiTek Posi-Strut webs which are first pressed into the timber and then nailed in place for additional strength. The floor deck used is an approved FR build flame retardant deck and in addition the ring beams, packers, noggins and strongback braces are also treated with an approved FR build flame retardant. This flooring system, used in conjunction with a Category C wall framing system, will deliver a Category C compliant construction.
In December 2012, the UK Timber Frame Association (UKTFA) published important guidelines concerning the construction of timber frame buildings in urban environments.
Developed in partnership with the Health & Safety Executive, the guidelines assessed the potential impact of a fire during the construction of a timber frame structure, on neighbouring properties. In broad terms, the guidelines define three different proximity categories. Category A builds are sufficiently far from neighbouring properties to pose no significant risk and therefore “standard” timber frame construction and “standard” floor systems, including Posi-Joist, can be used. Category B builds are nearer to neighbouring properties and steps are therefore required in the build method to reduce the spread of any potential fire during the construction phase.
The guidelines state that in addition to other floor systems, Posi-Joists can be used in Category B builds provided that a Fire Retardant floor deck is fitted. In the case of the most confined urban sites however, deemed to fall into Category C, the original guidelines did not include a Metal Web Joist or I-Joist flooring solution. As a result, MiTek’s technical team has been busy in the intervening months developing Posi-Joist Fire-Safe with the aim of having it approved as a Category C floor system. Two successful fire tests for this system were conducted in June of this year leading to the formal approval which took place in July 2013.
