NB We're not experienced builders or architects. We have as many nationally accredited, government sponsored qualifications in building, architecture and carpentry as an Iron Age house builder. We (Laura and I together with Peter and Julie) have read a little and applied some logical thinking. This is a recounting of what we've been up to and not an instruction manual!Part 3
And along came a chainsaw. Very useful bit of kit. Speeds up tree felling enormously and takes care of jobs like lopping off surplus height of the uprights. Hurrah. So this week's visible progress is 12 posts looking a lot like last week's blog, but shorter. This means we've decided on wall and door heights (1.5m and 1.7m ish). We measured from the ground up and marked each post as the site seems fairly level. Tying a string to one post and running it all the way round following the marks shows how inaccurate that technique is as the blue string resembles a sea scape of gently rolling waves, but it also allows quick adjustment by eye and re-marking. Invite the chainsaw to the circle and hey presto, similar height poles.
All along we've been thinking about how best to fit the wall plates (the horizontal pieces that join the uprights together). The instructions in the book, Tony Wrench's "how to build a low impact roundhouse", use metal straps and nails which we don't have. His diagrams show a lap joint of two wall plates above the post. We thought we might improve on that by creating a cup for the roundwood wall plates to sit in. That didn't work at all well and resulted in felling another tree to replace the massacred upright. We also worked out that the method of connecting a sloping wall plate (from a wall post to a door post) would require fatter roundwood than for the horizontal ones. And we also needed 12 main rafters. So chainsaw to the woods for useful bits and firewood offcuts. Many trees have been sacrificed in the making of this structure.
We're using sweet chestnut because it is the best of the types of tree in this wood. Our alternatives are silver birch (straight but rots quickly and not as strong) or hornbeam (really wiggly and also known as "ironwood", the clue is in the name). So although sweet chestnut is marvellous at resisting rot, right up there with oak, and strong enough for the purpose, it does have one property that can be useful or a serious problem. It loves to split. This is not good when it is holding a roof up. After lots of discussion with Peter, also not an architect, the design of the joints for the wall plates have been modified to ensure that the plate that is uppermost on the lap joint has its lower section resting on the top of the upright. Otherwise there is no strength given by the lower half of the round wood and being sweet chestnut, it'd just split along it's length. We're also introducing some metal. We wanted to keep the structure very natural but it is sensible to tourniquet the posts and plates with wire (we'll be using free fencing wire that was getting chucked out) to reduce the likelihood of a collapse if big bad wolf huffs and puffs.
So once the wall plates are jointed, at awkward angles as there are 12 not entirely straight poles forming an irregular dodecagon, we'll peg with seasoned sweet chestnut. We're making the pegs at the moment. We have a homemade froe, from a hinge strap, which is coping with a bit of the job but not as much as it should so the pegs are taking quite a bit of ax time. Unconventionally, we'll not be making them a snug fit as we don't want to encourage any splitting in any of the structural timbers. A fantastic website
, with lots of maths bits, shows the architects' view on how these frames work. It says that there is no outwards force from the roof. Our interpretation is that we can have loose pegs. Tony Wrench had tight fitting 13mm steel bars in his joints and metal strapping with many nails to further secure it but his was a bigger house...
And away from the heavy detail of our guesswork and to the MICE in the caravan. Peter and Julie, our friends here in France, owners of the woodland and commissioners of the roundhouse, were at the caravan today. Looking for dogfood, Julie opened the oven (I can rationally explain this action but I won't). She found the reason for the night time quiet. This is Glis Glis, an edible dormouse, hibernating. Unfurling its tail caused it to snuffle and wrap itself up again in a ball of fluff about the size of a large fist. As well as being grey rather than beige, they are far bigger than the dormouse. The edible dormouse is the one that the Romans fattened up, stuffed and roasted. We've found lots of mushrooms and this dormouse is already in the oven...
Wild food anyone?