charley brentnall

14.03.15 | preparation for construction

#projectlaceygreen

A couple of weeks ago we received the great news that the planning application has been approved by Wycombe County Council (phew!) – so it was time to stop considering plan b options, and focus on preparing for construction over Easter. Having made a few mock-ups of the proposed mortise and tenor lattice structure, I wanted to think through the practicalities of building the whole structure in this way, and get some extra advice. The first person I spoke to was Tim Lucas, a partner at Price Meyers Engineers, who has been involved with projects at the Farm and is a visiting citric for ADS6 at the RCA. Tim had some concerns about the strength of the joint, and the effect of shrinkage as the timber seasons. He talked through a couple of other options, one of which would be to add steel braces on either side of each lattice junction, which could become a interesting design feature. In this scenario, the timber pieces wouldn’t have to actually interlock, but could butt up against one another – meaning there would be significantly less cutting and less CNC machining. Another alternative would be to build a set of portal frames, replicating the system of prefabrication and erection that we used in Chander Nagar. Although at the start of the project I had wanted to do something more complex and challenging that this – now that the construction dates were getting closer, the simpler the solution, the more appealing it seemed!

However, before moving away from the lattice design too readily, I wanted to run it past Charley Brentnall, a timber framer who I first met back in 2012 when Alex, Ivar and I ran a workshop at WOMAD festival. As well as having a huge amount of experience working with ‘green’ (unseasoned) timber, he’s also involved with the Design+Make program at the AA’s Hooke Park, and has led a number of projects involving schools and children. Seeking his advice was also a great excuse to go and visit him Colerne, Wiltshire – a beautiful part of England I hardly know – and take a look at the workshops at Carpenter Oak & Woodland. After talking the design through, Charley seemed confident the mortise and tenon joint would work well, and felt that the steel would be a bit of a cop-out in terms of timber craftsmanship – as well as being expensive, and unnecessarily involving another material and a whole other fabrication process. He had some very useful input into the construction process, and gave some great tips like oversizing the timber lengthwise (so that the pieces can be moved on the CNC bed to avoid knots near the joints), and making the lattice within days of the CNCing (so that the timber doesn’t shrink too much in the meantime).

Feeling much more confident about the design after the trip to Colerne, it was then time to nail down the exact dimensions and joint details with Steve, so the calculations could be done and the final timber cut-list prepared. We also need to finalise the foundation details, and drainage strategy – all of which have to be submitted to Wycombe Building Control, who’ll make sure that the design is in line with the current UK Building Regulations. Thanks to the generous support of Helpful Hirings in Thame (who lent us a hydraulic hole-bored for an afternoon) we dug an exploratory pit on the site, to check the soil type and required foundations. Yesterday, Keith and his son started dismantling the sports storage shed, so it can be relocated adjacent to the sports pitch – next week we’ll start marking out the site and hope to find a friendly tree surgeon to do the necessary pruning before construction starts!