Ecological Shelter Build

Hello to all who took part in the course this summer. Thank you so much for your companionship and hard work during the course, we hope you enjoyed it as much as we did. As promised, albeit late, here is a  breakdown of the design and build, some links related to what we learned,  some photos a review and update of the build and a message from Paulo. Hope you find it useful :)


PicasaWeb Slideshow

There was some confusion over what to build for this course , we wanted to demonstrate how to build a simple structure using  local recycled and affordable, ecologically sound  materials that would not require specialist skills to implement.  After much deliberation we finally rested on the decision to build a small structure serving as an outdoor compost toilet and  a storage room which would also double up as a chicken house for the winter and  cap it with a green roof for growing plants that require poor shallow soil (something which is non existent in our permaculture gardens:). Our design will not win any prizes for innovation that's for sure and i am pretty certain  it would not pass building regulations either but we are beginning to love this humble building and the chickens have nothing but happy clucks to say about it. So lets take a look at the design .      

The Design 

The slide show below shows the layered elements of our design, and what we  achieved during the course. Missing from this plan is the  4th wall which was to be made of timber planks and the partition wall, between the toilet and the chook house, which was planned to be completed at a later date. On the last slide you can see the diagram Paulo drew and below we will go through every layer on the diagram and talk a little about the materials used. 

PicasaWeb Slideshow

                                     A foundation, B stem wall C  plate  D straw bale walls E roof plate F roof joists G green roof H soil and plants I cob rendering

  •  Foundation
 We wanted a foundation that would drain the water away from the building so opted for rubble infill. You can use any waste rubble , river stones or broken rocks but the more uniform the size of the  pieces are and the more flat edged they are the better they will hold.

trench filled with river stones 

The foundation was dug 45cm deep and 50cm wide below where the 3 straw walls would sit and filled 3/4 with rubble we collected from a dried out river and 1/4 with flat edged stones kindly donated to us by some road builders. The flat edged small stones are much better suited for foundation and if you are building anything with considerable weight an absolute must. When digging the trench the valuable top soil was placed around the garden  and the subsoil was piled nearby for later use for the green roof and ramming the tyres with earth. We did not need a full trench foundation for the fourth wall as the only weight dispersal and  contact with the ground would be from four wooden posts. Therefore we placed pads for the posts to sit upon. we used lime crete ( a mixture of lime, sand and cement) but you could use concrete or large flag stones.     


  • Stem Wall

  The stem wall sits on the foundation and protects the wall from direct contact with water. Its important it is level and stable. We used old tyres and rammed the inner part with the subsoil from the trench we dug for the foundation. You really have to ram that earth in hard and you know when you are there as the tyre appears to be inflated.  

Tyre stem wall 

The center of the tyres were than filled with stones as used on the foundation. Tyres are very easy to get hold of just ask around tyre repair garages, they will be happy to be rid of them but make sure they are all the same size. If you are planning on building an habitable house than 2 layers of tyres are recommended. we used one as it seemed sufficient for the buildings purpose.      

Ramming the earth into the tyres
  • Floor Plate

The floor plate sits level on top of the tyres and is the base on which the bales will sit. It is also used to compress the straw bale layers against the roof plate when a bracing cable is passed through the bottom over the top and tightened up to sandwich the bales in.   

Its quite simply a planked base which we drilled holes in to drive hazel stakes sharpened at both ends  through the holes into the stone infill of the tyres. The hazel stakes were thinned out  from the hazel trees in the nearby mountain. As you can see in the picture below half the stake was fixed into the rubble and the other half was protruding upwards to secure the first course of bales. The planks ,as with all the timber we used for the build, was from a pine forest nearby to us and milled locally. 

stem wall with the floor plate and hazel stakes in place ready for the bales 
  • Straw Bale Wall
The straw bale wall went up very quickly and in hindsight more time should have been given for this part of the process. We got whipped up into what is commonly referred to as "straw bale frenzy" where everyone is eagerly piling bales on and staking them into place. As a result of this our walls were not as strong and straight as we would have liked them.

placing the first layer of bales onto the hazel stakes 

 On the first layer we placed each bale on the stakes and the bales were trimmed down to fit onto the base and placed as snug to each other as possible. We than made staples from the hazel poles. To make the staples you simply beat the hazel stake with a heavy hammer  30 cm in from either end which softens the fibre in the wood and than you can  twist the wood so that it forms a staple. The next course of bales was placed to create a running bond i.e  to overlap the joints of the lower layer as in brick laying. 

  A hazel staple
There was another group making the 2 window boxes which would sit on the second course of bales. The window boxes consist of a wooden box for the glass window to fix into. it should be designed so that the box should be the same height as a bale and should fit over 2 half of the bales below to continue the running bond. We put these in place and continued with the next 3 courses of bales.

 A window box 

We were driving longer stakes to fix the 3 or 4 layers together however this contributed to the unevenness of the wall as the stakes were creating there own rigidity. We should have stuck to short stakes to bind each layer to the other and stapled each bale horizontally to each other.

   Getting the window boxes in 

Normally you can get your bales for half price in August  if you collect  them from the field but be sure to have somewhere totally dry to store them. We got our bales from the local farmer directly from the field. The farmers baling machine has seen better days and was not producing the uniform bale size and  compression suitable for bale building but we made do.   

  • Roof Plate
The roof plate is a timber frame construction planked both sides and  sits on top of the bale walls. 

The proud carpenters bring down there masterpiece 

Once placed on top of the bale wall, bracing cables are placed through the floor plate right the way over the top of the roof plate. We used  pieces of hose threaded onto the cable to stop it from digging into the wood on the corners. The cable is than tightened up so that the whole structure is bound together and the bales are further compressed. Our attempt at this failed as the cable we used was not strong enough and kept snapping under tension .   

The roof plate is on and the structures strength is tested 

  • Roof Joists 
The roof joists provided the fixings for the roof and front wall support beams. We notched the beams and joists and fixed them together with butterfly bolts. A 2% gradient was desirable for the flow of water off the roof and this was achieved by notching a little deeper toward the back end of  the fixings.

The roof joists being put into place

We than attached the front columns onto the roof joists using screws and bolts. The column base sits onto the lime crete pads we had prepared earlier.

 The front columns with stacked functions of being a quadruple crucifixion apparatus :)

The uprights being put into place

  • Green Roof
We managed to find some very cheap  offcuts at the mill which were suitable for decking out the roof. We than placed a layer of 4mm ply wood over the planks to create a smooth surface for the membrane to sit upon. This was only necessary because we was using a polythene membrane for the soil to sit in and the rough planks may have punctured the sheet. Ideally one should use a pond liner type rubber for the membrane but the cost of this membrane would have worked out more than the rest of the build put together so as we were trying to stick to a budget we decided on folding up a polythene sheet over and suppressing weeds using a weed membrane on top of the soil. Time will tell whether this was a wise decision. We used wide planks nailed onto the side of the roof joists to create a tray for the soil and something to attach the polythene onto.  


The roof floor and  polythene in place and ready for the soil to go in 

It would have been great if everyone could have seen the soil going on the roof and the first plants going in. We placed a thick layer of straw on top of the polythene so that the stones in the soil would not puncture it whilst we was walking around and used the sub soil from the trench to fill the tray about 10cm deep. In the back right corner we made a hole through the wood and polythene and fitted a drain pipe down so that the water on the roof could drain away.  We ended up getting it done just before the sun set and enjoyed the new view from the garden of the sun disappearing behind the Stara Planina from the roof.

The view from the  green roof 

  • Cob Rendering
the cob goes on

Whilst the carpenter crew was busy making up the wooden structures the rest of us were preparing the outer skin of the building which would protect the straw from the weather. We used a cob mix (curpitch)  which we obtained from crushing old adobe bricks we found discarded at the local dump. This is a great way to save time and energy as gathering the raw materials to make this mix and the actual work involved mixing it up is very intensive work. The adobe bricks which can be found discarded all over Bulgaria have already been mixed perhaps 100's of years ago with suitable amounts of clay, sand, straw, manure and sometimes small stones  to create a strong binding substance but you may need to add more straw if you want it to hold better  and remove the stones for comfort when plastering by hand. It all depends on what type of brick you find. Some small sample should be made beforehand to see how the material feels and acts. If you cannot find old bricks or want to make the mix yourself than you will need to find suitable soil for excavation and than carry out the following simple test.

The Drop Test
Mix up a little of your mixture or soil  with some water than grab a handful of mixture and work it into a small ball. Always add small quantities of water as a very wet mix will not give a true impression of your mix untill it drys out a little.    
  1. Hold your arm directly out in front of your body at shoulder height.  
  2. Drop the clay-sand ball onto hard ground in front of you.
The ball should hold together quite coherently.  If it splats flat the mixture is too wet or you have too much clay and you should add more sand to dry it out a little.  If the ball breaks to pieces it is too dry or you have too little clay in the mix so you need to add more clay or water.  Simple!
When you squeeze the ball next to your ear you should be able to hear the grains of sand rubbing together ,if you cannot add more sand until you can and repeat the test. 

This will give you a good base for your mix now just add straw and manure for extra strength.

Review and Update 

    Our design was something of a hybrid between a load bearing and timber frame and although it serves its purpose as a shelter/toilet and winter chicken house we would not recommend doing it this way if you were making a bigger building. As it stands we had to prop up the back of the roof with pine poles as the weight of the roof was causing movement. The straw bales would have held the roof without a problem had there been 4 straw bale walls but the woodwork involved in creating door boxes similar to the window boxes we made would have been excessive for the purposes and the floor space taken up by four bale walls for such a small interior area would not have made sense.     
    Since the summer we have been busy working on the build to get it ready for the chickens and protect it from the winter weather. More cobbing was required to seal all the cracks and we have planted a few more plants on the roof. The front wall has been built using off cut planks from the timber mill and the inside partition has been added. The Chickens have moved out of the tractor and into the Shelter and the outdoor toilet is ready for use. In the spring we will plant around the building and  trail melons up onto the roof so they can ripen in the full sun. We will also plant up  a variety of Creeping Thyme thymus polytrichus, thymus capiatus, thymus serpyllusonto the roof making the most of the poor well drained soil we have up there.

PicasaWeb Slideshow

We had great fun building the shelter and the whole experience provided a good  platform to explore natural building further. Thank you especially to Paulo for teaching the course and his patient help with the preparation and tx again to everyone who helped out. See you soon hopefully     

Message from Paulo

Dear Permaship, friends and fellow building companions


 Okay, so now we have had time to consider the building and watch it start to become a place rather than just 4 walls with a roof, do we consider that as a project it was a success? What went well and what didn’t? If we built the building again what would we do differently? And  does the building qualify as ecological?


So lets start with the positives (as these I believe outnumber the negatives). Firstly and most importantly, we as group achieved a fantastic result. We constructed a simple building from nothing in less that 4 days and by the end of the last day, (which sadly those who left earlier did not get to see), we had 4 walls plus a green roof in place and with the added element of two pine poles to stabilise the back wall. Over the course I watched people who at first seemed shy of using tools, progress to cutting mortise joints  in wood (and good ones too), making fairly expansive bits of carpentry and working together to get the building up. This is the point of building as a group – to have fun, to work together and to learn new skills. From this perspective and as a learning (and fun) experience I think the course was a great success and this would not have been possible without Permaship who deserve credit for their willingness to try new ideas. From a design perspective, it appears that the chickens are now happy in their new home and you can enjoy a nice view from the outdoor toilet. Also the materials have a very low carbon footprint, are sourced locally & at a generally low cost or even for  free. Most of them can also be reused but more of that below. This is a definite success and not easy to achieve with more ‘modern’ building methods.


Okay, so what of the negatives? Well, the design of the building was wrong and tried to incorporate a basic method of building (straw bales) with a much lighter and more intricate method; timber frame. The reasoning behind this decision doesn’t need discussing – it was an experiment and ultimately the union between the two methods didn’t work so well. However, as the overall construction of the building is simple, we were able to  make some quick decisions to rectify our main worries – that is to shore up the rear wall which had started to lean. This was probably a result of the front wall being timber and the load or weight of the roof being passed on to the walls became uneven - plus  the sheer amount of keen people who were climbing all over the roof to bang in nails probably helped in the wall leaning! So we simply added some timber poles and stone foundation and then the building started to ‘sit’ better and was able to fully support the green roof. Our mistake was to use the timber front wall – next time use 4 straw bale walls! In fact this was the main problem of the build; straw bale buildings rely on the connection of each wall and a strong roof to stay together and by removing a wall, we created a lot of extra problems – especially in altering the inherent structural rigidity of the building. It meant that the weight became uneven and this is what caused the leaning. Our next building design must evolve! I would say that the other issue were the program of works which meant that some people were left sitting down whilst others almost took permanent residence in the earth / cob pits! This was because we worked so well as a group at certain tasks but didn’t have quite enough time to get every task done correctly. Some parts, like the wood work, take longer and therefore we were always behind time which meant less time for relaxing.. But hey,  its not a perfect world and time isn’t always abundant and sometimes working under pressure is a great way to bring people together… so we still achieved.


So what would we do different next time?  Simple, take more time and use Straw Bales for the walls and timber for the roof. I also think that the wall plate is overly complicated and could be simplified – ours was just a little too heavy to move safely, and possibly just a little too short in length. Again it’s the relationship between the precise (wood) and looser (straw) that means that time must be taken to ensure that everything is right as the project progresses. I would also reconsider using tyres as I found the rammed earth method to be a little random – how do you ensure that each tyre is ‘pressurized’ or filled up equally? I would perhaps use stone next time.  Otherwise I think the majority of the building is sound.


So is the building ecological? In a word yes, if you allow certain materials to be reused rather than reprocessed. The stones in the foundation, straw and hazel poles  in the walls, timber in the wall plate, floor plate, window boxes, front ‘wall’ and roof can all be reused or recycled. The earth on the roof and in the tyres can return happily to Permaships beautiful gardens and even the wire can be reused. Which leaves just the tyres and plastic to consider. Well the tyres were taken from the waste stream and would have probably ended up being burnt so we can argue that by using them in a building we have at least mitigated against their impact. And the plastic? Well, it was a cheap and usable material that we needed for our roof and overall relates to less than 1% of the building cost and mass so I leave you to make your own conclusions. Mine? Well, 99% is almost good enough, especially when looking at concrete, steel and brick… buildings have to last and we need a waterproof layer in our roof hence the choice of plastic.


To end this course I would like to thank everyone who attended and helped run the course and it was a brilliant event of which the memory will stay with me for ever. All the people of the course should raise a Rakia or fruit juice to their fine combined successes in creating a building that has individuality and most importantly, possesses a spirit which is firmly part of the place we have all helped to build.


Oh and I must also congratulate the chefs  for the fine food and once again Paul & Sophie for doing what they believe in and of course the ongoing support of my family...


One love!


Links for further reading   One of the best online resources 

The Cob Builders Handbook  Excellent book on Cob(curpitch) 

Building with Straw Bales  A straight forward and invaluable guide to building with straw    A good introduction to Green roofing