The Boiling Wells roundhouse roof- eight months on.

Here's a couple of images of the repaired roundhouse roof, eight months after the last of the sedum had been laid. It's looking good! 

We had to put some black net around the back of the roof, as a fox or some other wildlife was getting up there and pulling up the sedum mat to look for food. The very dry summer last year also gave the roof a bit of a hard time and meant that a few buckets of water needed to be thrown over it. However, it has grown well to cover a lot of the timber terracing and hopefully next year will see it flourish again.

Willow weaving and a little living sedum roof on the strawbale urinal roof at Boiling Wells,St Werburghs, Bristol

We had a bit of sedum mat left over from repairing the Boiling Wells roundhouse roof, which meant that the strawbale urinal building could also get a living roof ready for the 'Spring Celebration' on Saturday!

Just thought I'd post a few images of it here:

While Simon and the Tuesday woodshop crew were putting the finishing touches to this roof, in another part of the site a group of young people were busy weaving our willow hedge, to tidy it up ready for the summer. Most of them have been to Boiling Wells before and it's great to have them back again:

The Boiling Wells roundhouse roof. Ecobuilding vs the elements!

Work has been slowed up a bit on the roundhouse roof recently thanks to some pretty unhelpful weather. First heavy snow, then heavy rain and then strong winds- it seems like every week there's a severe weather warning! It makes it pretty tricky putting on the cut sheets of pondliner and the underlying straw without it getting soaked or blowing away.

But then, it is winter here so what should you expect...

However, the pondliner has now been fitted to two-thirds of the roof, which will be the waterproofing layer. When this is finished, it will be  covered with geotex and then some plastic netting, to give some footing for the gravel, soil planted with low-growing herbs and sedum which will go over it.

 The 'Greenseal' EDPM pondliner has been a bit trickier to work with than expected, no tape seems to want to stick to it and so I'm gluing the sections of it together with Sikaflex and will cut the old DPM polythene waterproof layer into strips and then stick that down over the joins.

Still, things are moving forward slowly-watch this space!

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 http://carvingswithstories.blogspot.co.uk/2013/01/fixing-boiling-wells-roundhouse-roof.html 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.

Cheese!

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!

Fixing the Boiling Wells roundhouse roof

Over the last week, I've been hard at work repairing our roundhouse roof.
It was originally built with a very steep pitch and the turves laid on it were about 12 inches (30 cm) thick in places with little drainage. As they got wet, the weight of the roof grew until it pressed down hard enough to break one of the windows!

There was also a problem with drip points from the roof going straight onto the ashwood rafters, which were beginning to rot as ash isn't durable when repeatedly soaked outdoors. 

This was making the roof potentially dangerous as the screws holding the fascia boards on were close to failing, which could have allowed tonnes of earth to cascade off the roof.

 So, a bit under two years later, we have some insurance money to finally try and get it right!
The first task was stripping the roof back to the underlying timbers. We discovered that the original builders had built it with slab wood overlying the ash rafters, then carpet, then straw, then damp proof membrane gaffer (aka duct) taped together, then another layer of carpet then finally turves dug up from around the site.
The turves came off fairly easily by just sliding them off on the underlying carpet. Digging the resulting piles up and moving them about the site was a lot harder!

 We then stripped the black plastic damp proof membrane off and saw it had ripped in a few places. We will replace it with EPDM pondliner, as this is more durable although more expensive. Under the plastic was the straw and then more carpet. These both acted as insulation and will be replaced when relaying the roof.

By the end of the fourth day, we had stripped the roof, fixed in concentric terracing timbers (to try and give some break in the roof gradient and stop material creeping down the slope), relaid the insulating carpet and covered it all with the DPM to keep it waterproof until work can recommence next week.

Many thanks to Oisin, Amrik and especially Simon for all their hard work and help this week.