Finishing the roundhouse roof rebuild at Boiling Wells!

Today, the last of the sedum mat was fitted onto the roof of the roundhouse. Hurray!!

The terracing timbers still look very new, but hopefully their appearance will mellow at the same time as the sedum grows over them, so that eventually the whole roof will look more 'organic'. The terraces seem to have helped solve the problems of the ridiculously steep pitch that the roof has in places. The roof also doesn't look too regular and symmetrical because the timber frame isn't, which I like.

There are three different kinds of sedum in the mat. Here's a picture of some of it:

We left sedum off the compartments just below the windows, as rainwater running off them would probably wash away any growing medium and plants during heavy rains. Hopefully the gravel will baffle such water flow a bit.

Now to get on with the next bits to be done: sorting out the cordwood wall and fitting doors.

The cordwood wall was put in unseasoned. As it has seasoned the wood has, of course, shrunk so that some of the pieces can now be pulled out of the wall completely. A lot of it is also ash and plum, both timbers which woodworm is very partial to.

I'm planning on spraying the wood with borax solution to deter worm attack and then lime rendering around the pieces. It may take a while, but it will sort out the shrinkage problem and I prefer the look of the lime render to the cob, to be honest. Lime render is also tougher than cob, which can be scratched away with a fingernail in places. I'm not sure when it will be done, as a lot depends on funding and  the number of helpers available.

Watch this blog to see how things go...

Fixing the reciprocal roof on the Boiling Wells roundhouse

Work has been continuing on the repairs to the roundhouse roof originally built by Shift Bristol at Boiling Wells.

There have been big problems getting any covering to stay on the roof. The pitch was far too steep, approaching twenty degrees off vertical in places! Therefore, we decided to build terraces of timber which are not fixed down onto the roof below, but sit on it. 

Landscaping textile and old carpet were used to protect the pondliner from being damaged by the timber and also to hopefully soak up some water and prevent the roof drying out too quickly in summer. 

The compartments in the terracing were then filled with a layer of pea gravel. They will eventually have a layer of substrate (70% ground up brick, 30% compost) put on that and, finally, sedum mat put on top of that. Some areas are too steep for even the terracing to help, so may be partially enclosed to make 'window boxes' that can be filled with soil and then have herbs planted in them.

We have been lucky to have had extra help in the last two weeks, from people who are currently unemployed through an agency called 'Pinnacle People'. Their work has been a massive boost to the repairs and moved things forward a lot. Thanks to all of them.

Phil (who was part of the original Shift build crew) and Simon also volunteered and helped a lot. It's a great feeling to see the roof starting to look like it's nearing completion.

Some thoughts for anyone thinking about making a similar structure, as the repairs (hopefully) near conclusion...

I have to say that if I were to build a roundhouse in the future, I don't think that I'd put a reciprocal roof on it. The irregular angles and pitches have been a pain to deal with at times and, although pretty, the whole thing is really a bit impractical.

The reciprocal roof is made using a support called a 'charlie', which is removed to drop it into place. This makes it hard to control the angle that the roof finally sits at, which is made worse by the irregularities in the roundwood rafters causing bumps and lumps in the roof. I will admit that more experienced roundhouse builders may have solutions to these problems, but I'm not aware of them.

These bumps and lumps have made covering the roof a bit of a nightmare - things that need straight lines (such as shingles or tiles) don't fit properly and living cover can slide off. 

One solution may be to use old tyres to make roof terracing, which Shift Bristol has tried on another roundhouse build. This would look okay in summer, but when the vegetation dies back in winter it has an aesthetic that is perhaps not to everyone's taste.

I'd be far more inclined to put a flat roof with a slight gradient (between 10 and 30 degrees) on a roundhouse. It would be a much easier, quicker build and far easier to lay sedum mat on and to maintain. 

It was great to have the roundhouse built at Boiling Wells and Tony Wrench, the Shift Bristol students and the volunteers worked very hard in less than two weeks to do it. The structure is attractive and interesting and it's been fascinating to learn about such things as lime rendering etc. when finishing it. 

I would say to any organisations looking to have such a building built on that kind of time schedule and by a similar group of people, most of whom are inexperienced in this kind of construction, that they really have to have a decent pot of money in reserve to correct problems and to finish the build off (with doors, floor etc.).  Bear in mind that these things will cost you in time and money - possibly at least a couple of thousand pounds. These roundhouses are not necessarily cheap!

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.