Friday, November 19, 2010

Roundhouse at Cwm Harry - on the road again

Now that we have the paths finished at Cwm Harry, save for a bit of packing down and final dressing, we're turning our attention to the ROUNDHOUSE. This is intended to be a gathering point, demonstration of sustainable building, teaching resource, tool store and of course tea break hut for the project.

We have decided to simplify the original design and go for a reciprocating roof, with sedum covering. The upright posts are already in place so its been a question of re-planning things from there.

Lianne, Sue, Wayne, Sharon, Jocelyn and myself putting in the upright posts earlier this year.

I've helped to build a roundhouse at Lammas, (see earlier posts: Nigel and Cassie's roundhouse and Simon and Jasmine's roundhouse.) I haven't been involved in the design before though, so this is a really exciting project for me. In my long erratic working life I've used my schoolboy geometry a lot in making all sorts of things, guitars, buildings, pyramids etc. etc... So the bit I find really interesting is the RECIPROCATING ROOF. This is a clever way of making a large span with no supporting columns cluttering up the space. It's also possible to make one with tree trunks pretty much straight from the forest, so it's low-impact and low-cost if you have woodland anywhere near you. A roof like this could be put on any shape of building, we just happen to like the round floor plan. Yurts, teepees and other round homes make very sympathetic living space; you don't feel you're stuck in yet another box.

In a reciprocating roof, each of the beams supports its neighbour. It's possible to build one with any number of roof beams from three upwards.

(This drawing is from an interesting site: The Pavilion)

The final roof structure is self-supporting and puts no outwards horizontal force onto the wall structure, so it is really clever. (Our upright posts form a twenty-sided polygon of about 19 foot diameter and I've drawn up a plan with ten roof beams. This gives a beam between every second post, which will work out symmetrically over the doorway. We'll have to kick up two of the beams to give space for a full height door but will check that works on a scale model first.

Here's the plan so far:
Roof pole plan, doorway and arch detail and side elevation allowing for full height door.

Looking up into Nigel and Cassie's roof with the main ten roof beams as well as  the secondary ten in place. The blue sky was a rare sight last November...
This is the interior of a roundhouse that Simon built one or two before his Lammas houses. The main beams are filled in with smaller lateral poles to take the weight of the finished living roof...

...of the house known as The Hobbit House, for obvious reasons.

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