Despite its embodied carbon, masonry is still the default construction method. What are the alternatives?
The UK’s appetite for bricks is growing. With Great British Brick Shortage reports in recent years, increasing annual production and import, and now news that the country’s largest manufacturer will invest across its two sites to ramp up manufacture even further, it seems we can’t specify enough of them.
While bricks have existed in various forms since Roman times, common use dates back to 350 years ago, when after the Great Fire of London timber framing in the City was banned and replaced with masonry in the London Building Act of 1667. Similar Acts rolled out in cities across the country eventually evolved into the Building Regulations which still define our practice today. From the mid-1900s, cavity wall construction became more commonplace, originally to avoid penetrating water but still used now to incorporate insulation. Dividing the structure into two thinner walls weakens the masonry, but by the end of the century this had become compulsory in new masonry construction.
So now we have fewer fires and warmer homes. But is there any logic to the way we are building now, and can we do better?
A three-storey masonry-built house would typically have 50% more embodied carbon than an equivalent timber framed, larch-clad house. And the same house using masonry just as cladding still has 30% more than the timber option.
Modern brick construction has developed from a straightforward brick, mortar, brick approach to a complex system involving numerous accessories: wall ties (to tie back together the wall we have split into two), bed joint reinforcement (to strengthen the inherently weak bending capacity of the thin wall), movement joint ties with fillers and sealants (to allow for the expansion of the brickwork and contrasting shrinkage of the concrete blocks hidden behind), steel angles or boxes (to accommodate long flat openings), steel windposts (again, to strengthen the divided wall), head restraints, column ties… it is difficult to see the modern logic in this heavy, layered construction.
Yet it remains the prevalent form of construction, with 2.4 billion bricks, producing 2.6 billion kgCO2e, used in the UK each year. This huge amount of energy is of national importance. In our efforts to decarbonise, how can we continue to produce something that, if abolished, would have the decarbonising effect of two medium nuclear power stations? Or 25% of all offshore wind farms?
A three-storey masonry-built house would typically have 50% more embodied carbon than an equivalent timber framed, larch-clad house. And the same house using masonry just as cladding still has 30% more than the timber option
Steve Webb and Rosie Mounsey are at Webb Yates Engineers