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Thursday 24 January 2013

Fitting a new window in the roundhouse's cordwood wall

There has been a bit of a break in fixing the roundhouse roof, thanks to some heavy snowfall (a note to readers in Canada, Scandinavia and other areas used to snow- more than a couple of inches (5cm) of snow in the UK and everything comes to a grinding halt).

(No, really!)

In the meantime, we decided to fix the window which was broken by the weight of the overladen roof pressing down on it. See the post at for the full story...

 Anna and I, together with the young people that are volunteering through their schools to help on the project, assembled a new window in the Boiling Wells barn last Tuesday.

The previous day I had collected together some offcuts of  European Larch from my workshop and routed a groove along each one to take the replacement toughened glass double glazed unit, which had arrived at the farm site. The volunteers and I then cut simple mortice and tenon joints to join them together . The assembled frame was finished with linseed oil and left to dry.We also had enough time to make pizzas and cook them in the wood-fired pizza oven. Yum!

When assembled, the frame looked great!

Today, Simon and I fitted the window into the roundhouse wall. It was a bigger job than it sounds!

The previous window was a glazing unit slid into slots cut in the surrounding cordwood logs. There was a lintel made of three sweet chestnut sticks, the central one of which was also grooved to take the top of the glazing. The adjacent, surviving window was put together in a similar way, which you can see below.

To fit the new window, we needed to brace up the sweet chestnut stick lintel, as it supported the cordwood wall above. We then had to the rip out the surrounding notched logs (many of which were nailed to nearby posts) in order to make room for the new frame. The wall underneath also needed to be partially rebuilt, to give a level surface for the window frame to sit on.

We put in a temporary brace, then inserted two sweet chestnut poles to make new lintel bearers. We also thought that leaving the old lintels in would give more support to the wall above and protect the new window from going the same way as the old one...

We could then fit the new window, using builder's metal strap to attach it to surrounding logs and posts securely.


Finally, we mashed some of the removed dried cob with water to make it reusable and started to fill gaps around the new window with a central straw insulating core and cob on the outer sides. 


We need to finish putting the cob on (nightfall stopped work) but the new window looks great! To be honest, we all prefer it to the one slotted into the logs. The contrast between the straight lines of the frame and the cordwood wall looks better and less slapdash than the previous window. It is also easier to remove and replace the window if needed (important in a community-used space).

 I'm quite tempted to put a couple of layers of lime render over the cob in the cordwood wall eventually, as it looks neater in my view (although the metal builder's strap may need to be protected from the corrosive lime mix). It will also fill some of the gaps left by the unseasoned logs originally used, which have shrunk as they seasoned. Some can now be pulled out of the wall completely. 
The logs should also really have been debarked before being used in the original build but time was tight for the Shift Bristol crew who built the roundhouse and so some things couldn't get done.

Before lime rendering, I'd also like to spray a borax solution over the logs in the cordwood walls as a mild insecticide. Some of the cordwood logs used are from fruit trees such as plum, which will probably get hammered by woodworm pretty soon if nothing is done to protect them.

So Simon and I had a pretty busy day today! However, the snow did come in useful in one way. Since there were no groups of young people on site, we could keep our incentives to finish the job nice and cold until work was done and we could enjoy them...

Next job, finishing that roof!


  1. The whole job seemed to be a level more difficult than fitting in a window to a concrete house, especially with the uneven lines of the hole. But the replacement window still looks organic to the whole structure, don't worry. It is just better now that you added insulation to it. What are those things you were stacking up inside the roundhouse, by the way? -->Kermit

  2. Hi Kermit,
    It certainly has been a job that grew in the doing! Glad to hear that you like the look of the new window though, thanks.
    I think that the things inside the roundhouse were the pieces of carpet that we took off, which lay underneath the original turf cover. It was full of weed roots, some of them pretty hard to get rid of (such as bindweed), so unfortunately we couldn't recycle it when relaying the roof. It did come in handy covering the mud to help us move about though! There's also a pile of straw in there, which was reused for insulation between the carpet and the pondliner. Along with tools, bits of scaffold tower, ladders etc.
    Nice to hear from you and all the best,

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  4. It looks like Simon was really enjoying your window project. You can tell by the way he smiled that he’s really having fun. Well, you guys must’ve been very excited with the project. It’s not everyday that you have an improvement project like this in the roundhouse. I hope that everything went well, even with the roof
    Allyson Ripple @ D&M Roofing