Last week I spent another glorious day surveying trees in woodland near Abbey St. Bathans in the Scottish Borders.
These are to be used as posts and beams in two new buildings that I am designing for Happy Days, a nursery in Dalkeith. But we’re not just looking for any old posts and beams – we’re looking for unmilled timber structures (and especially branching timbers). That means that the trunks are not machined, or regularised, but left in their original state, knots, bends, forks and all. This a good use of otherwise redundant or underused wood.
The woods belong to Willie Dobie of Abbey Timber, which is a small sawmill located at Abbey St Bathans.
I was inspired by the website of Whole Trees Architecture and Structures, an American company that specialises in using raw trees in a range of projects including hypermarkets.
Little did I realise when embarking on this project how difficult it would be. The construction method is almost completely alien to the UK timber industry and specifiers. Whole trees are not recognised in design standards used by engineers.
So it was with great difficulty, and after an extraordinary wild goose chase the length and breadth of Scotland that I tracked down a ‘grader’ who is qualified to certify the whole trees that Willie Dobie and I had selected for possible structural use in the nursery. I discovered that there are only a handful of graders in the whole of UK capable of grading whole trees, and all of them based in England.
Iain Thew of Dossor MCA, an engineering firm based in York, joined me and Willie in the woods last week to assess whole trees and identify which ones had the right load bearing capacity. This was done visually by assessing the position of the branches – and therefore the knots – and carefully measuring limbs and trunks.
Luckily the sun shone on us for both my visits and we found all the trees and round poles that we needed – 18 in total – a mixture of oak and larch. The UK hardwood grading rules only cover a very limited number of tree species – oak and chestnut, while larch is the only UK grown species that can be visually graded for strength.
I will be returning in the next few weeks to witness the trees being felled, and to choose which branches to keep. By the time the nursery is complete, I will have followed the journey of each tree from its original woodland setting to supporting the finished educational building – less than 40 miles away.
The building warrant application for the buildings has been submitted and we hope to start work in late Spring. The oak posts will be carved with some woodland motifs such as treecreepers’ foot prints spiralling around the trunk.
Both Willie and I hope that we have somehow burst the logjam and that more people will consider using this cost-efficient and sustainable construction method – which permits the use of otherwise redundant trees – and that the UK’s constrictive regulations can be brought into line with those in the US and continental Europe.
Main image: Whole Trees Architecture and Structures