Clearing up Document B confusion
Confusion continues to surround the impact of changes to Document B on the supply of laminate glass in balustrading. Mark Norcliffe, joint managing director of Cornwall Glass Manufacturing, discusses.
Regulations are there for the right reasons but they do have unintended consequences. This is very much true of Approved Document B and its amendment in December 2018, which bans the use of combustible materials on the external face of buildings.
There are very few that would argue with the sentiment that sits behind the amendment; Grenfell was a tragedy and a watershed moment for construction.
Controlling the spread of fire by banning the use of combustible materials in taller buildings is a logical response in the aftermath of terrible loss.
There are, however, consequences for our own industry, and specifically in relation to laminate glass because laminates are classified under the amendments as combustible.
This creates a problem for anyone supplying glass balustrading at height. EVA, PVB or SGB interlayers are part of the course of supply, however, under the amendment, these can no longer be supplied in buildings which are 18m or more tall.
It certainly creates a problem in higher rise and multi-storey installations. While toughened glass is tough, it isn’t indestructible. Should it break, the laminate is there to hold the glass together. That’s important for those at height but also those who are passing underneath it.
The authors of the amendment have also faced criticism, because there are exceptions to the requirements set out in Document B, including for window frames and glass, which does seem somewhat incongruous given the extensive use of laminates in IGUs, especially in larger and higher rise applications.
Those critics of the change argue that the inclusion of balustrading under the amendment is based on a misclassification and assessment of EVA, PVB and SGB laminates as a stand-alone product, not as a component part of one.
Tested in isolation, neither meet fire classifications, while the amendment also doesn’t recognise a laminated glass panel as a ‘single’ or ‘complete’ product.
There clearly needs to be an assessment of risk of ignition of a laminate which is sitting between two pieces of glass, and the advantages it delivers in increasing safety at height, and again below it.
The thing that I would emphasise for the majority of customers, particularly those working in home improvement markets, is that there are no restrictions on the use of laminates in place unless buildings are 18m or taller; five storeys and up.
At the same time, it’s really important to consider the installation to identify the right thickness of laminated glass for the appropriate loading requirements and fixings.
In most domestic and light commercial applications, laminates deliver significant benefits in balustrading. You can offer a high degree of protection with toughened glass in a glass infill application but we always encourage our customers to go down the laminate route because it delivers an added level of protection, particularly anything at height.
Requirements for balustrading in domestic applications are covered by BS 6399-1:1996 ‘Loadings for Buildings’ and BS6180:2011 ‘Barriers in and about Buildings – Code of Practice’, which set out standards for line loading.
This is the principle that balustrades will need to withstand different line loads for different applications, from domestic applications right through to public spaces.
The measure of line load is made in kilo Newtons (kN) for every metre of length. This will vary based on application and definitions under BS 6399-1:1996 – housing, office and public function.
In a domestic or residential application, this is set at 0.74 (kN) per metre, equating to around 75kg of pressure per metre of handrail.
It appears more daunting than it is and our technical team are happy to sit down and work with our customers to help them meet technical requirements.
Cornwall Glass Manufacturing made a six-figure investment in a our Tema LPB2536 laminated glass line at our Highbridge site (one of three IGU and glass processing sites we operate) in 2018.
This has increased our flexibility in laminate glass supply, including the capacity to process individual sheets of 2,500 x 3,600mm.
The interlayers used by Cornwall Glass Manufacturing have also been classified as: B-s1-doB fire retardant; S1 ‘no/low smoke production’; as well as D0 ‘no burning droplets produced’.
Putting the discussion of regulation aside the popularity of balustrading has seen immense growth in the past three years.
We’re supplying infinitely more laminates, and particularly balustrading, because of its appeal to end users and reach in light commercial applications.
The debate and discussion that is taking place in relation to the amendment on Part B is an important one. There is an opportunity for review and consultation.
For the majority of our customers, however, it isn’t going to have an impact on their business.