CONCERN IS mounting in the industry over the use of downlights in ceilings made with i-joists instead of traditional timber joists.
I-joists – pre-made and pre-cut wood-fibre sections – have replaced traditional solid-timber joists in around 80 per cent of new homes in the UK over the last 20 years.
House builders favour them because they arrive onsite cut to exact lengths; they don’t twist or bow like conventional timber; and they’re easier to handle and drill through for electrical cables and pipework.
But i-joists don’t perform the same as traditional timber construction in a house fire.
There is simply less material to burn once the protective layer of plasterboard has failed, causing the floor to collapse sooner.
Numerous i-joist and plasterboard combinations have been tested and certified to achieve 30, 60 and 90-minute fire ratings but complications arise when downlights are installed.
‘If the downlights are not good at insulating for fire or are not installed properly, then there’s a weakness there and the fire will get through sooner than 30 minutes,’ says Luke Whale, technical director at the Staircraft Group, Europe’s only i-joist manufacturer.
‘If you’ve tested a downlighter with solid timber joists, the result doesn’t necessarily translate to a floor made of i-joists’.
Crucially, the National House Building Council says it won’t accept fire certificates for downlights installed in homes using i-joists unless the luminaires have been tested on all the i-joists currently available on the market.
The issue has been highlighted and championed in the trade by Efixx, the leading electricians’ website and YouTube channel. It’s calling for more clarity and better documentation.
This week Efixx warned the trade: ‘If you’re installing a downlight which was tested within a traditional timber construction, the NHBC won’t sign the off the completion certificate’.
It recommends that if in doubt, electrical contractors should use fire hoods over the downlights.
Fire-rated downlights come in 30-, 60- and 90-minute versions depending on their manufacture. They’re tested in special laboratories using gas burners which take their temperature up to 900C in 20 minutes.
The Lighting Industry Association has recently set up a dedicated task force to tackle the issue.
The Fire Rated Downlight Task Force (FRD-TF) comprising LIA members who manufacture downlights and technical experts from the LIA.
The task force aims to coordinate a response to the NHBC and attempt to resolve discrepancies between test methods and the various European and British standards.
WATCH THE EFIXX VIDEO HERE: