Materials for a Roundhouse

If you want to build your own roundhouse, you must consider issues of planning permission, who is to help you, design, siting and many other subjects which I am covering in a new book A Simple Roundhouse Manual by Tony Wrench (moi). This webpage is a rough form of the chapter on Materials, because few people appreciate how many materials go into making the simplest roundhouse, so once you have your materials ready you are half way there.I am assuming in this text that you will build with the aid of a group of people, but one or two persons with a bit of decent equipment could do it. A group is more fun, though, and is much quicker.

Get your building materials ready in advance. If you are of a mathematical or nerdy state of mind, and enjoy understanding the nature of systems, check out Critical Path Analysis. There are no doubt useful apps, applications or programs available for your computer to help. The essence of CPA is to work out the most efficient way through the varied range of functions of a project such as site preparation, ordering materials, designing, manufacturing, assembling, having things delivered, etc etc. Some elements take a long time, so need considering early on. Others, like buying nails, are fairly flexible unless you plan to build over a public holiday. (It happens). The most efficient way through involves all things being ready and prepared when they are needed, and no-one sitting around waiting for something else being prepared, or stuck in the ground, or posted from America. If you have ever cooked Christmas dinner for a large group successfully, you can do it. The main point to bear in mind is that the longest or most critical operations are usually on the Critical Path. You may need to think quite hard about whether something is on the critical path, but practise using the idea a bit and it becomes obvious. Obtain the Turkey, ensure the oven is big enough and works, and Prepare the Turkey are all on the critical path. While the turkey is cooking you can prepare potatoes, vegetables etc etc. But did you make sure you had enough potatoes? Have you ever run out of a critical ingredient as you were cooking a feast? It is that kind of thing, and no less important. A simple roundhouse requires very few operations compared with most building projects, but nevertheless you need more materials than you would think. So, get your building materials ready in advance.

First, look at what is locally available. I have known people fall in love with the idea of a straw bale house and plan it all out without first asking whether small straw bales can be obtained locally. If you live next to a forest and hundreds of miles from arable fields, please don"t go for straw bales. If you live surrounded by farms with little barns brimming with straw bales in surplus, don't go reading my book and think "It's got to be cobwood!". Be flexible. In cities you can find astonishing recycled stuff to build with, if you can get permission. There are homes in other continents built from scaffolding planks, driftwood, plastic bottles….
So much information is available to you. My experience is mainly on building simple roundhouses with a roundwood skeleton, cobwood or straw walls, and turf roof, so that is what we will discuss here. If you have access to a thousand old wine bottles, twenty oil drums, two hundred car tyres and a helicopter perspex canopy, however, build em in! Your roundhouse will be unique - these words are not reality, your build is.

This may sound a bit weird, but I have noticed that for most people inexperienced in building anything, it takes quite a jump of the imagination to realise that they will take part in forming an actual building out of a mere pile of stuff. When we gather for our first circle on the site, I recommend everyone to take a minute to look at the space, the view, the landscape, the fact that no building is there. Take a picture of it - the 'before' view. The not-building you are looking at.

I am going to plump for the possibility that you will find a good forestry contact, a source of clay and sand, and a volunteer with a chainsaw and chainsaw licence. There is a local recycling centre with carpets and old windows, and you have a good local Freecycle system to tap into. Why be so mean? Why be scrabbling around using old windows rather than fit new ones? Why sweat over roundwood rather than pop down to Jewson's and blow a few grand on a proper wood order? Why has it all got to be so cheap?? Houses cost hundreds of thousands, don't they? Well, sorry, but semper funquet. It has got to be funky. Always. I'm really sorry.

Does your roundhouse have to have a wooden skeleton (henge)? Could it just be load bearing straw bale or load bearing cobwood? Well you can do without a skeleton, yes, and you can make a perfectly good roundhouse with load bearing walls.
Here is a roundhouse built as a course at the Planit Earth site near Penzance in Cornwall.

Planit Earth ~Straw bale roundhouse, Cornwall. Photo David Knight

This is a strong wooden insulated deck a half meter off the ground onto which is built a 5.5m internal diameter roundhouse of straw bales, pinned to the deck and each other. The walls are lime rendered and the roof is a reciprocal frame sitting on saddles on a wall plate.

The den in winter

Next picture is our den, a roundhouse of 4.5m internal diameter constructed of load bearing cobwood walls on slate stem wall, raised floor of wood, and reciprocal roof resting on saddles on a wood wall plate.
I will discuss briefly this way of building later in the Manual but I don't really recommend it. In both above cases the walls felt very wobbly before the roof was on. Yes the render acts as a structural component over the straw, and yes the buildings feel solid and secure now they are finished. With the cobwood den, the walls were held together with cob, so that needed to be reasonably dry before taking the weight of the roof. It was never quite clear when this would be. We got away with it, it looks and feels great and has not subsided or shrunk or anything, but unless your roundhouse is 3.5 m diameter or less, I prefer both cobwood and straw bales as infill to a good solid wooden henge skeleton. Uncool, but hey.


carrying wood to Shift Bristol build in Bath

For a standard roundhouse wood will be the greatest volume of material, and probably the greatest expense. Use roundwood where possible. It is stronger than sawn wood, looks good and grows like that, so you are more likely to get a good deal with it in its pre-processed state. Same with most things. Ben Law explains the advantages well in his book 'Roundwood Timber Framing'. The very cheapest way of getting wood for your build is to get it yourself from the forest. Wood really is a renewable resource. Trees are out there, taking in CO2, turning it into cellulose, and growing all the time. If you are able to operate over the longish term you can actually get wood for free by buying a piece of woodland, managing it for a while by thinning some of the more overgrown or overplanted areas, and selling it again, usually for more than you bought it. The wood for this house and our den both came from this method. I know not everyone can do this, but if you have formed a group to build several roundhouses, it would definitely pay you to go direct to source and buy some woodland.

The wood for our standard roundhouse is in several forms:

henge crosspieces

Annie standing in front of a henge

diagonal bracing
David ties together a reciprocal frame of rafters

tripod, charlie and temporary braces
sills and frames
benches, ledges and shelves.

Benches in Cornwall roundhouse

Let us start by looking at wood for posts.
We shall look at two ways of making the skeleton - posts in holes (the old way) or posts on pads (the new way}. Posts in holes need to be of wood that has its own preservative against rot, such as oak, chestnut or, at a push, larch. For posts on pads you can still use oak and chestnut, but you can also use some other woods which are reasonably rot- resistant such as black locust (I have never used this but Ben Law reckons it is the future), eucalyptus, larch, and Douglas Fir.

How many posts?

The number of posts will be the same as the number of rafters, and number of spaces in the wall where you can have doors, windows or benches, and the number of pieces of fascia you need on the eaves. Not enough rafters/posts will give you large spaces at the eaves, ie large spans to cover and to bear the weight of turf. Too many rafters will give you such a small gap between posts that doors and windows may not fit adequately. Number of rafters will also affect the pitch of the roof. The other factor coming into play here is the width of the roundhouse. Bear in mind that I am keeping things simple here. You can have extra rafters, or extended rafters to give an extra circular space beyond your basic circle. Let us look at two options: simple and extended circle for larger buildings. This shows the common limits of a simple roundhouse, using a group of people to construct, so using rafters that are physically liftable. I usually consider 3 metres the longest span for any rafter in this context. If you are an architect or engineer and wish to use enormous thick or laminated rafters with greatly enhanced structural strength, go for it. I am just talking about the range of lengths and thicknesses that I have used and know to be workable.

Taking as a rule of thumb that a rafter needs to be approx the internal radius of the roundhouse plus 2.5 m, and also taking into account the need for a reasonably small span at the eaves but a decent space between uprights, I would suggest the following table: Rafter numbers and lengths for different sized roundhouses

For an internal diameter of 3.5 m, 8 or 9 rafters of 4.25 m
Ditto 4m, 10 or 11 rafters of 4.5 m
Ditto 4.5m, 11 or 12 rafters of 4.75 m
Ditto 5m, 12,13 or 14 rafters of 5 m
Ditto 5.5m, 12,13,14, or 15 rafters of 5.25 m
Ditto 6m, 13,14, 15 or 16 rafters of 5.5 m

Another consideration is: odd or even number of rafters? Yes, I know this very house has thirteen posts and major rafters, and it is quite possible to build with odd numbers, but, in particular when it comes to building the new way, with posts on blocks, an even number of posts makes it all very much easier. I'm not stopping you going for odd numbers, dear reader, but you'll have to be especially creative when it comes to completing the henge crosspieces if you have an extra post to connect to.

If you want a bigger internal diameter than 6 metres, ie an extended circle, please put plenty of design work into where you want extension rafters, how much to slope the extension, where to put doors and windows, etc. I have limited experience with extended circles, and would only say that it pays not to plan too grandly at first. Get to know the principles and the stresses at work in something small and manageable before you build the four metre tall, eight metre wide ballroom.

So let us choose a Standard Example of a roundhouse 5 metres internal diameter, with 12 posts.


12 posts.
Length? For the old way you need approx 60 cm of the base in the ground, and then an estimate of the height of your henge, plus any extra to allow for a floor. With a simple floor insulated with Foamglas or other non-wicking insulation, I allow 240mm. So 800mm in the ground plus floor depth of 240mm plus height to henge, allow 2m. Total length 3040mm. Add a bit,say 60mm, for wonky cutting, and we have a post length of 3.1m. Putting posts on pads saves you 600 mm off this in theory, but it is always good to ask for a bit more than you need, so say 3m or stay with 3.1m.

This is going to annoy you but my favourite way of communicating widths of roundwood is in body parts. Why? Because only if you are a builder or carpenter and deal with measurements in mm all the time can you resonate with something like '180mm' and see it in your minds eye. At least '7 inches' or 7" is more handleable to many natural builders, so I might talk in inches a bit, too. But for roundwood widths, lets stay with body parts.

Post thickness is : Thigh at base; lower thigh at top. So in mm and inches, min. 7" 180mm base, 5" 130mm top. Whose thighs? Yours, not your great granny's. You can go bigger if you want. Chunky posts look good.


Here again, there are a few ways of making the henge, and we use different cuts of wood for each.
Henge option 1: Full roundwood.
If you have the time and inclination, and some carpentry skills, and a facility for setting up one or more sawbenches that are truly level, you can go for crosspieces of roundwood, of comparable thickness to posts, ie thigh thickness. The first set of crosspieces link six of the uprights to form six 'arches', which are either on pads or are stuck in the ground. There is a simple upward-facing joint on the upper corners of each arch. The circle is completed by shaping ends of the downward-facing crosspieces to make an overlapping joint. These are fiddly to make, but look good, and will be discussed later. The henge made in this fashion looks very tidy, as they say in Wales, and has a good consistent feel. If made in oak or chestnut, and braced by strong roundwood diagonals, the structure can look nicely indomitable. If you are going to have any of your crosspieces be load-bearing, ie you want to extend your first circle into pods or an outer circle, I would use this method. The photo above of Annie eating an apple shows the henge in one of the Cornwall Planit Earth builds.

Henge option 2 and 3: Half round or flat crosspieces.
The slowest part of option 1 is making joints above each posts that are accurate in all three planes. These 3D joints are difficult.
You can get the joint above one post where all faces touch perfectly and it sits completely flat on its post, yet the other end, on the next post, has great gaps or sits really badly on its post. This is because each end was made on a slightly different plane. We can eliminate this problem with care in setting up the sawbench and in marking joints out, but you can cut out at least 60-100 person-hours by using wood that is roundwood sawn down the middle, (option 2) or is not round at all, but has been sawn as a slab of 3" wood with parallel sides (option 3). I will talk about this later, but for now, you need to think about quantities for your timber list.

So, for the list:
Option 1 : 12 off roundwood thigh thickness, 2 metres long. (You need to allow for distance between post centres in Chart 1, plus enough to reach a bit beyond the outer edges of each post. 2 metres will cover it} They need not be same wood as posts, as no danger of water splashing onto them, but need to look consistent with the posts. They will be visible. Option 2: six thigh thickness 2 metre lengths cut straight down centre, to give 12 off 2-metre half rounds. Option 3: twelve hard or soft wood sawn slabs, preferably with the bark on at least one edge to match the posts. 3",80 mm thick, at least 8", 200 mm wide, and 2 m long.


You will need something to brace the posts diagonally to give strength to the structure and stop it twisting under the stress of extreme winds or falling trees. It pays to be flexible in your design so that the most common type of wood, or the one most in surplus, that nevertheless is strong and looks good, can be used. I usually over-order rafters, so we have some spare for diagonals, and the tripod and Charlie. (see below). Sometimes you may have a surplus of posts, so you choose the strongest or straightest for posts, and use the wiggly ones for diagonals. Oak is great for this. In one roundhouse, built in the heart of Longwood, near Lampeter in Wales, the challenge was to use as much as possible of the Lawson Cypress that had been removed from the wood the year before. Our local wood miser miller Adrian was willing to come out into the woods for a day with his machine and turned out over a hundred fine planks of Lawson Cypress, high in its own fine aroma preservative, two inches thick and over three metres long. We could use these planks to give a simple wall to the shelter, but fixed on the diagonal to also serve the function of bracing.

Iain inside the shelter at Longwood

So, for the purpose of the timber list, put 'diagonal bracing' in, and make sure you have something that you have over-ordered that you can use.


Rafters need to be of a long, straight, strong type of wood that has a good tensile strength. Don't use woods like sycamore or alder that get very brittle when dry. Use woods that are known for their structural strength:
Oak is good but heavy even when seasoned over two years or more. It is strong, but usually a bit wobbly. You might be lucky in well managed oak woodland, such as abounds in France.
Ash is lovely, but give it time to season, or it will bend too much and stay bent. Ash wood is very easy to strip when freshly cut, so ideally you would select and cut the trees yourself - easy to do with simple hand bowsaws - strip the bark immediately, then leave somewhere dry to season for a few months.
Chestnut is great if you can get it.
Larch is good. Again, strip the bark straight away if you can.
Spruce, similar. Douglas fir, lodge pole pine too. There is no need strictly to strip the bark from these woods, but they will be visible in the ceiling of your roundhouse, and stripped they add light and look good.
The main thing about rafters is that they must be strong and flawless through their whole length. For length, the guideline I use, as stated above, is INTERNAL RADIUS PLUS 2.5 m . Thickness: lower thigh at base, knee or calf at top.
I always order more rafters than I need, to allow for Charlie, tripod, spares, and diagonal possibilities. Don't worry about being left with loads of roundwood at the end of a build that you don't know what to do with. Cobwood walls use all thicknesses of wood. Your wood stove isn't fussy, two years down the line. Do you know how much total waste was generated building this roundhouse I sit in now? One plastic sack full.

So, rafters: for our default 5 metre diameter (2.5m radius) roundhouse with 12 posts allowing for spares:
20 off 5.5 metre lengths of straight, strong, high tensile strength, stripped and seasoned (preferably), lower thigh at base and knee at top.


The other need you will have will be for cordwood, if you are using this style of wall. Cordwood is my favourite wall infill material, and there are many examples of it in these buildings. One of the good things about cordwood is that you are not relying on the wood to do anything other than fill a space - nicely, yes, with good insulation, yes, but we are not demanding resistance to anything or particular strength. We simply cut cordwood of any thickness into a consistent length. I use 16" or 400 mm. If you live in a climate prone to very cold winters (there have been roundhouses like this built in Sweden, Alaska, Russia and Canada) you could go to 24" or 600 mm logs, and when you build your wall put two separate layers of insulation in the inside cavities. When I say 'any thickness' I mean it. If you can get hold of some giant cedar or thuya logs that take three people to lift, use them. They look great. Cordwood walls may be of any type of wood. Literally. Poplar, aspen, cedar, laurel, thuya, rhododendron, sycamore . . . you name it, it will be fine. If you have oak or chestnut logs, use them at the bottom of your walls where some resistance to damp is more useful. Wood with lots of air in it is good higher up, for its insulation value. It is best to season the wood for a while before using it if you can, so that it will not shrink after a few months and leave gaps to fill in. So, how many logs? This is almost impossible to answer because it depends so much on the size of log and how much of the wall area you are devoting to cobwood. For myself I would go for a large pile of different sizes and if you pushed me for a number it is 600 logs, all of 16". Yes, six hundred. Get sawing.


Sarking is planking laid side by side, on top of the rafters, to form a wooden ceiling. You could, of course, order a big load of tongue and groove to do this, or you could, at the other extreme, roam the woods for a few weeks in the winter and come back with a big load of willow and hazel thinnings that might be 2-4 metres long and be of thumb to wrist thickness. These, pinned onto the rafters and then covered with a tarpaulin, or finest calico or silk (only kidding) make a perfectly acceptable, nay, beautiful ceiling.

BUT this kind of roof, though cheap and fun, is not acceptable to building inspectors in any of the systems I know - it offers too little resistance to flame. Wood, slightly surprisingly, is much better. I have also got to really like the look of a wooden ceiling, so recommend you do it by means of SLABS. If you can track down a good source of slabs, you can take a giant leap forward up the Simple Roundhouse Ladder. Slabs appear in dozens of the pictures here. A perfect pile of slabs will cost about £50 delivered, and will have several long 2" x 2" poles, a range of 2" x 1" slats, several giant pieces of tree side with bark on, maybe two feet wide and three metres long (disgraceful clash of measuring systems there - sorry), as thick as your arm in the middle and almost unliftable, and dozens of 3 metre lengths of almost parallel foot-wide softwood, bark on one side and clean sawn on the other. A nice cedar slab makes a good door frame.

The thing is, it is almost impossible for me to say exactly how much you need. You have to find the source, negotiate a delivery price with the sawmill, then take a great leap in the dark. There is not even a standard load. The best builds are those in which the builder has ordered an extra-ordinarily large quantity, say upwards of twenty loads, from a sawmill which takes in many types of wood including oak and cedar. If you have the possibility of doing this, please do. It may cost you £500 or so, but you will get all your ceiling, fascia, benches, window sills and lintels - everything you need. It may even be of educational benefit. On our two Cornish builds the owners were lucky enough to be given the entire slab contents of a woodyard that was closing down. We not only had all the wood we could possibly need for two builds, but the children present, after watching us for a few days, constructed to completion, with no adult assistance, a beautiful den for themselves.

So, for your list: At least ten loads of slabs.


The only other wood you might need is if, after surveying the big pile of slabs, you still cannot satisfy any need you may have for wide, smooth areas of sawn wood that is good for benches, wide window sills, or door frames. You may need to add to your sawn wood order for an appropriate number of 20" wide , 2" thick slabs of sawn wood, max 2 metres long, of cedar, douglas fir or similar. All of this will be visible and add to the tone of the building, so aim for a consistent style. If you ordered hard wood for option 3 crosspieces, for example, you could order the same for frames and benches. Or you could try a hard or soft wood that is not known for structural use, but is very tasty in this context, such as sycamore or alder.


5 tons

2 tons.
Many places have clay underground very nearby. On several builds we have simply gone fifty metres from the site and dug it up. In the Forest of Dean we had to go a quarter of a mile down the road. In Cornwall the local college had a very active pottery department that threw out tons of the stuff. Top quality for free. Don't assume you can leave this till later, though. Silt won't do. Take the time to source this fully.

5 tons approx.
This is for your stem wall. Urbanite is broken up roads or buildings, and it pays to find the right person who can deliver this stuff to you just like that. It is easier near towns or cities. Spend some time on getting the right contacts, eg local council, reclamation yards, local farmers. If you are building the new way, on stone pads, make sure you have good strong pads of sufficient quantity to stand your posts on. Don't trust that there will be enough there when it comes to it. They are on the critical path. Put them aside in advance. Keep a few spares in case some crack.

WINDSCREENS (for the skylight).
The ideal is two big coach windscreens. They are preferably identical, so one can fit above another, and over a metre at the narrowest point. 1.2 metres or more is preferable. You used to be able to ask a bus depot for windscreens with a reasonable degree of success. Considering the number of buses and coaches on the roads you would expect quite a large choice, but, owing to stringent regulations about glass recycling, the opposite is true. Best way of getting a windscreen is to ask at your local depot when the replacement windscreen van is due to arrive. They seem to come about every six months. Be there when the van comes, with your own large vehicle and with cash in your pocket, and may the angel of Lucky Deals be with you. Two or more perfect matching windscreens gains you more Sourcing Points than any other single act on this build. Award yourself whatever prize you can allow, take the rest of the day off, and protect your new windscreens with shielding in several dimensions. If ever I get to be sent back in time, and wish to gain instant demigod status by earlier residents of this planet, I will take with me a cigarette lighter and a coach windscreen. (I know this is a mild digression, but have you ever looked at the struggle Ezekiel has in his first chapter in the bible trying to describe a sophisticated piece of air transport in pre-industrial language?) Windscreens are such precious, unappreciated gems in our world that they attract Murphy's Law like no other artifact. If something can go wrong, it will. So anticipate the most unlikely twists of fate. I kid you not. If you fail totally in your quest, order a Perspex dome 1.2m across from eBay. It'll cost you £300 or so.

I used to be purist about membranes and went for a single rubber 1mm thick pond liner for this house, which cost £650 fifteen years ago. They are heavy and do the job, but we have found that something - we are unsure if it is ants boring with great dedication, or some plant with very sharp roots - is capable of making very small but perfectly formed holes in the rubber after about eight years. I have since switched to using double sheets of agricultural heavy duty silage plastic, which is incredibly cheap - a 11m x 28m roll costs ¬£38 in 2013 in Wales. It can easily be punctured, however, so make sure you have plenty of:

or equivalent membrane protection.

Freecycle or your local recycling centre are a good source for this. You need carpet under and also above the membrane, so work it out. It is a lot of carpet. Get it in advance, or you will hold up a whole team of turfers on a lovely day near the end of your build. You calculate the area of a circle by pi x radius squared. Our 5m diameter roundhouse will have a 7m diameter roof, so the radius is 3.5m. Pi is 3.142. Add 20% for the slope of the roof and overlaps, and this gives you 46 sq metres. Call it 50 sq metres. Double it, for under and over the membrane, and we are talking about 100sq m. of carpet. This is quite feasible, if you have a good team and a large vehicle or good trailer.
You can use Polyfelt, which is a geotextile made from recycled plastic bottles, instead of carpets. One brand name is Terram. You can buy it fairly cheaply from garden centres or online. We have it on our den, and it cost about £50.

As I mentioned earlier in this chapter, small straw bales are not necessarily easy to get in your area. If they are, and you choose to make your walls and roof insulation from straw bales, you need to calculate how many bales you need. Traditionally, a small bale is 36" long, 18" wide and 14" deep. A wall of bales set on a stem wall will be six bales deep. You know from your previous decisions how wide your roundhouse will be, from centre of the posts. So, staying with our five metres, we can estimate that a full circle of bales would be 15.7 m or about 17.5 yards (one bale is about a yard long). But two of those bales will be where the door goes, so 15.5 x 6 levels might be a reasonable estimate,which comes out at 93. You will probably want spaces for windows, so allowing for a few broken bales, failed halves etc, 90 won't be far out.
If you are using straw bales in your roof, one straw bale has an area, viewed from above, of 0.46 sq.m. If you were to cover your entire roof with bales you would need 119, but you don't need to insulate above eaves that are outside the building, so you could make do with 100 bales. I personally am moving away from straw for roof insulation, mainly because of the challenge of preventing warm moist air moving up through it and condensing on the underside of the carpet. We have it in this house, and it is fine, but building regulations don't like it, so I would rather not use it for now, if you don't mind. If you can get big bales, you can use this in insulation in the roof, with the same caveat. You will need two large bales for the roof.

So we are back to our 90 small bales for the walls.

If you plan on having cobwood for a large part of your walls, you will still need some straw to make a strong cob. Ten bales will do for this. If you can't get small bales, one big bale will be fine.


Things like screws and nails are not to be ignored, as they are intrinsic to this design. If you are a total wood peg and dovetail joint purist, you could make a roundhouse from just wood joints, string and pegs. If you wanted to go seriously celtic or native american, you could bind joints with rawhide, which is an amazing natural material sorely ignored by our society, but I have never tried to squeeze my way into the stream that goes from abattoir to skin processing, to curing, to leather processing. Rawhide would have to be sourced before the curing process. It would be very interesting to get a good source of rawhide, as it is very flexible when fresh, and can be lashed and tied, then dries very strong and hard. Someone will reclaim rawhide as a natural building material soon. Let me know please if you do.
Failing that, it is good to have a reasonable supply of screws, in particular, to start with. Screws that are long, won't sheer, and that are suitable for using with oak or chestnut, ie coated or stainless steel. Timberlok screws of 150mm and 200mm length are also very useful. Get two boxes of 25 in each length.
The other thing you will definitely need before you start is threaded bar with appropriate nuts. You will need it to hold the reciframe together and to brace the henge, so you won't get far without it. We start with about 5 metre lengths of 12 mm or 16 mm threaded bar with 50 nuts and washers.
Many hardware suppliers and builders' merchants operate on a very fast turnaround time, so this is one area where you could usually afford to have enough to be going on with for a few days, and order more when it is clear what more you need.

Allow at least £300 for fittings.


It definitely pays to spend time sourcing your windows. Find where your local glaziers work, and where they put out stuff they no longer need. Sometimes you may need to haggle for a good unused but wrongly measured double glazing unit. Other times, like the six matching single glazed windows that made three double glazed windows, in our den (pic above), you can get them for free. Another good source is to phone glazing unit manufacturers themselves.

If you have freedom to incorporate highly funky elements, eg for a kids' playroom, try your local recycling centre for washing machine windows. Two of these, one facing inside and one out, make a fun window at child height.

washing machine window in forest tots shelter in Forest of Dean

If you know you just want a lot of glass window, collect dozens of units and trust to creativity. On the first Cornwall build we had a very mathematically gifted participant who measured all 23 units, marked each one, then arranged them so that we could incorporate them into one long curving sweep of window, disguising the difference in length by a gradual increase in height from the east, to max height in the south, then decreasing again towards the west. Sometimes I think the effect is a little bit public library, but hey, it's beautifully light. Here is the work in progress.

windows of different lengths fitted to look consistent in Cornwall Planit Earth

Lastly, opening windows or just units? One or two opening windows with fitted frame gives more flexibility, but they are often rather naff materials like uPVC. You can hide this though eventually with a nice coat of lime render. These windows at Feed Bristol are virtually unrecognisable from their original appearance.

roundhouse at Feed Bristol

Of course, if you were particularly lucky on your windscreen quest, you can use some of the big, curved, new coach ones for windows as well as skylight. We have seven built into our house. Just give yourself plenty of time to source glass in advance.


Unless you are building load bearing walls of cobwood or straw bale onto a wooden deck, which is not really the style of build talked about through most of these pages, I think you can accept that your floor is so not on the critical path that you could source the materials later. Another reason is that most of the time we are thinking in terms of a group of people working at the same time. More than three or four working on a floor at the same time could well drive you mad. The critical path only comes relevant again if you intend to use newly sawn wood for your floor, when you will need to take seasoning time into account. This is because you need to let floor planks season and shrink before you fit them. Yes, shrinkage can be substantial. A hardwood like oak will shrink by over 10% across the grain, and 1% with the grain, so your 200 mm wide oak boards could be down to 180 mm after a few months in a warm, dry and well aired stack.


You will need a big roll of jute cord, as sold by agricultural suppliers for baler twine. Try and get a natural substance rather than nylon or plastic because all the little spare bits will compost or burn without harmful effects, and because natural cords make better lashing. The fibres grip better. Get this asap, rather than wait then have to shop around.


If building on a green field site, mow, cut or strim the whole site then remove the turf in foot squares and stack carefully. Don't make the turves any deeper than the four fingers of your hand. More than that and you are putting too much weight on the roof and too much weight on the turfers' muscles throwing the turves up. You can get away with even two fingers thick turves if you have to, but you lose some resilience for moisture retention in dry weather.


I'll be honest with you. As yet I have not found the perfect insulation to go on top of a conical roof with bumps and ridges, and under a membrane and turf. There will be the perfect stuff out there, maybe being used by indigenous builders somewhere, or being experimented on in the University of Kassel, Germany, which seems to be the world leader in turf roof design.

What we need is some material which, ideally:

- Comes in lightweight rolls at least two metres wide, ten metres long, and between 100mm and 200mm thick
- Is made from natural materials as a bye product of some other process or uses recycled organic materials
- Can be bought, found or imported very simply and locally somewhere near you
- Has excellent thermal insulation properties
- Can be cut and shaped using a sharp knife
- Is impervious to water vapour
- Will rot down at the end of its natural life, ie when your building is demolished or dies, and be a nutrient to the soil, with no pollutants.
- Is cheap.

Well, it's worth asking, isn't it? It spurs the imagination. Maybe you've got some already.

In or near towns and cities, reused sheets of Kingspan insulation meet many of these points, but it does not rot so is a problem to future generations, not to mention our own. It is not that flexible, but can be fitted on a roof under a membrane as good insulation. Here it is under cedar shingles

 Yoga house eaves edge

On the Feed Bristol build, where we used it, as soon as we found a few used, free, sheets of this stuff lots of people in the group remembered they had seen a piece at the back of a friend's yard, and we did the whole roof from donations of spares. It cuts and tapes together easily, and is fantastic insulation. I hate it.

If you choose a material which allows water vapour through it, such as cellulose products like Warmcell, wool, coir matting or straw, you are going to need a whole network of slats and supports to allow an air flow over it but under the membrane. So far I have avoided doing this because life is too short. We have not had condensation problems in our roof of 14 inches thickness of straw over tarpaulin. Maybe we should have had. If things get too complicated try looking at the problem laterally. I am really glad that there are people out there researching the dynamics of condensation and striving for the ideal of the perfectly insulated passivhaus roof and it is an important quest. It is just that Semper Funquet forbids me personally to get that nerdy. There is an ecovillage in Europe - I shall be no more precise - where houses have been built to extremely high insulation standards. At some point prices for chasing perfection get silly. The most expensive, and most insulated, house cost over 400,000 euros. Are its owners now hanging out in T-shirts in the best ecohome in the country? No, the whole damn business was so stressful that they split up and no-one lives in it.
So do some research for yourself. You may find the new/old material or method that has eluded me.


We are still talking about things to be sure you have in advance. As this is primarily for a group build, you may find that you need more of one thing, so be inventive. You can also choose how simple you want to go. In the Shelter book 'Builders of the Pacific Coast' there is a chapter on the building of the traditional long ceremonial houses of the native people of the north-western coast of America. (page 111) "At the heart of northwest coast building is the cedar tree, because it grows straight and tall in the rainy northwest rainforests, has straight grain, and therein lies the secret to its workability. Using only simple tools - wooden wedges, stone mauls, and blades of bone or stone - builders were able to split long, straight boards used for sheathing and roof decking in the days before metal.......To give you an idea of size: a Salish building discovered by Captain George Vancouver in 1792 was over 1000 feet long - almost a fifth of a mile. A longhouse discovered by the explorer Simon Fraser in 1808 measured 650 feet long by 60 feet wide."
Makes you feel positively nostalgic.

Let us start with the simple tools.

A maul is a log maybe 16", 40cm. long and about 7" wide - it could be off the end of one of your rafters or posts - with a 28mm, one inch, hole drilled into it and a long handle fixed into the hole. Smaller versions of this called mallets are also useful. Mauls are used for whacking posts, crosspieces, rafters, benches and frames to make them fit.
You also need a lighter version of the maul, using a piece of softwood but a similar size, as a 'persuader' for encouraging straw bales to sit neatly on each other and in tight spaces.
One or more wheelbarrows.
One or more flat and level sawbenches.
One or more saw horses capable of holding heavy posts.
Axes of all sizes. Include a wood splitter for keeping the fire going, or you'll look round one day and find some youth whirling a huge log around their head with your sensitive super sharp hand axe embedded in it.
All right - a spare axe handle.
Sharpening stone for tools. I like to bring a sharpener comprising four sheets of metal embedded with diamond dust in different grades, which are readily available these days and are quite resilient to hard and muddy use.
A hand adze. Sharpen it and don't lose it. Love it like your iPad.
A sledge hammer.
Several draw knives, for debarking roundwood.
Tape measures
Marker pens and pencils.
Bowsaws, handsaws, sharp.
Chisels, mainly wide bladed, ie 25 mm and upwards.
Set squares, as big as possible. You may be able to use a spare piece of plywood already cut to a perfect square, from which, by cutting diagonally, can be made two large set squares.
Two lump hammers
Six hammers.
Two heavy metal bars for hole digging
Cordless drills and drivers.
A heavy duty power drill for drilling down through rafter, through crosspieces and into post's endgrain. You can do it with a brace and long bit, leaning over the rafter on the top of the stepladder and putting your full weight on the brace, but not everybody needs that much character building, and not everybody is heavy enough.
A brace and bits.
Auger bit 400 mm by 16 mm
Two step ladders or more.
Several thin, 8mm, auger bits 300mm long for pilot holes for long screws.
(Why several? Because you drop it once, it breaks. You pull it out of the hole, and leave your finger on the trigger, it spins around too fast and breaks. You don't keep saying nice things to it? It breaks.)
Plenty of drill and driver bits.
A Surform or rasp
Hole digging spades.
Hole digging tongs, if you can find them. Makes light work of digging nice narrow but deep holes.
Hoes and mattocks for levelling the site.
A 10 metre long piece of clear plastic tubing 10mm or so internal diameter.
Two builder's spirit levels.
Hard hats.
Working gloves
Tough boots

And, maybe, a chainsaw or electric chainsaw with appropriately qualified and dressed person. Sometimes you can hire such a person for a few hours, and it is possible to build a roundhouse with this system, calling on the chainsaw person maybe two or three times during the build. Personally I find that if I can get mains power to the site, the use of a small but sharp electric chainsaw is very helpful at certain stages and saves a lot of time. But you can do without it. Remember - a longhouse 1000 feet long with no metal tools. It can be done.

That's it! You have got all this stuff ready in advance. You are half way there!

I hope this page has been of use to you. The quantities can be daunting but take your time. It has been quite a journey for me getting this page together. If you feel moved to send me any kind of feedback, here is my email.

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