Building with mass-timber
MY love affair with timber probably began as a child when I built shelters in or under trees and where I would hide when it rained. I loved the atmosphere, the smell, the sense of comfort and security that I felt.
However, beyond those romantic memories, there is sound reasoning behind considering building with timber, especially if you are wanting to create a home with a high degree of design flexibility and robust environmental credentials.
Should concrete and steel be still on your radar as possible building materials, you might want to consider their contributions towards CO2 emissions, in terms of their production and delivery, even if the steel has been recycled, as it very often can be.
Timber, meanwhile, is a naturally-regenerative product, that can be grown locally, with enormous carbon sequestration benefits (the storage of carbon dioxide or other forms of carbon to either mitigate or defer global warming) and insulation properties.
I am currently working with others to try and establish the manufacture of mass-timber panels for housing – from locally-grown, low-grade timber (most of which is currently made into pallets) – with the aim of creating local jobs, developing new skills, reducing the supply chain, expanding use of locally-sourced products and creating all-round economic benefits.
In particular, we are investigating CLT (cross-laminated timber), comprising panels layered on to each other at right angles, in our case using dowels to bond them together rather than glue, which would require checking whether it might release any volatile organic compounds (VOCs).
There are other mass-timber manufacturing techniques too, such as Brettstappel (also a dowel system), glulam and nail-laminated timber.
The problem in the UK is that such panels require to be imported from abroad, which comes with its own CO2 ‘price’. If there is an UK manufacturer of CLT, we have yet to discover it.
Mass-timber panels can meet the strictest of heat and acoustic insulation standards, provide considerable structural strength and spanning capacity (which allows for the aforementioned high degree of design flexibility) and are relatively light in weight (thus reducing the load-bearing requirements of foundations).
CLT can be finished to such a fine grain that it can double as the interior surface to a room, and, in terms of construction, requires only semi-skilled labour, raising the prospect of actual, (probably supervised) hands-on self-building.
It is also considered a ‘breathable’ product, an important consideration when considering the quality of interior ventilation and its possible impact on respiratory conditions.
Fire testing has shown that mass-timber burns itself out, while still retaining structural integrity. It is a misconception that, since it is a timber product, mass-timber is susceptible to spreading fire.
The carbon argument for mass-timber homes is, in my view, a ‘no-brainer’. Its place too in the mix of ingredients required to deliver Passive house energy standards (pretty much guaranteeing minimal household heating costs) can be vital.
Not only is timber a renewable resource, it eats up carbon as it is growing. It can also be easily recycled, not that it is likely to reach the end of its useful life any time soon: on the continent, mass-timber homes have been known to last hundreds of years.
And the oldest-inhabited house in the UK is timber-framed; I should know – I carried out a house condition survey on it a number of years ago.
Norrie MacPhail is a former builder who has spent the last 18 years as an asset manager within social housing and is, among other things, currently a trustee of a Scottish Borders housing association.
Image: Spruce and a Douglas Fir, side by side, image courtesy of the author