How to begin building with earth and straw

By now you must be champing at the bit to get building, so without further ado let’s get to it!

Firstly you have to make the earth and straw mixture; this is hard work and will beat a workout at the gym hands down! You will need a large board; I used a sheet of plywood. Throw some earth onto it, and then a few handfuls of straw – make sure the straw is not clumpy; pull it apart. Then add more earth, until you have a small pile. Now comes the hard work! Using a shovel or trowel you need to turn the mix over and around, making sure the earth and straw are evenly mixed – this is one LARGE cake mixture! Adding water slowly until it is sticky (sticks to your shoes in clumps!), but not too wet. If you add to much water then add more earth and straw to compensate. If you have a large paved area or a big board the easiest way to mix the earth and straw is to heap it in a mile and “tread” it. Imagine you are making wine by treading grapes – the mixture will stick to your boots and be evenly mixed. However you mix it it will be hard work!

Now for the fun part!

To begin you can probably use a spade or shovel to heap the mixture into the desired area, but once you have done the initial building you will need to get stuck in using your bare hands. Work the material as if it were clay, smoothing it and rounding it with your hands. It is impossible to make right angles or straight lines so don’t try, after all you are building a dome-like structure not a modernist block!

The oven will require walls that slope inwards and eventually meet, so after building the base you may find you need to use some timber shuttering or formwork. Use scrap timber and simply nail it – it does not need to look good or be built well as it will only be in use for a matter of days. Using the timber as a support slope the walls inwards. You will find you don’t need supports everywhere because the sticky mud and straw mixture binds together well.

If your earth oven will be in a pit as is mine then you may find that in order to fuel the fire additional oxygen is needed at the back of the space. To do this I have fitted a series of tubes and pipes into the back wall – so that I may provide a “human bellows”. It is my desire that when lighting the fire I can blow down these holes to get the fire started. Then once it is blazing oxygen should be automatically drawn down through the holes to fuel the fire.

Once you have built about 30cm high (12 inches) I would recommend stopping for the day. This may not sound like a lot of work for one day, but trust me it is! Digging the earth, mixing with straw and applying by hand is a lot of effort. Building above 30cm at one time may cause problems because the earth will take too long to dry out. On a hot sunny day it should only need a day to dry, but our British summers are not guaranteed sun so it could take longer. Do not build if the previous layer is still wet as it will collapse under the weight of itself.

Drying:

Over night I covered my structure in an old shower curtain as I was concerned that it could rain. Rain on a partially built oven could be disastrous and wash away half a day’s work! While the oven dries – during the day uncover it and let it soak up as many rays as possible, after all it needs to dry fast, not slow. Always re-cover the oven at night. We will solve the eventual problem of protecting the oven once it is finished in a few weeks!

How to make Rammed Earth Blocks

To make a rammed earth block it is quite simple. Firstly you need to make some “shuttering” or “formwork”. This is a simple box with no bottom or top. Just 4 edges.

I used old scrap chipboard from a disposed kitchen, but soon found that the shipboard splits under pressure! I would strongly advise the best quality wood you can find for this stage of construction. Because mine broke I bound it with string and tape, and it just about held out long enough to make all the blocks I required.

Next: fill the frame at about an inch at a time. Don’t go filling it right up, ram it down, and wonder why all the soil falls apart when you lift it off! Small and slow is the secret to making hand made bricks. After each inch use the ramming rod, bash it down (good anger relief!) and even stand on it – you need to squash the mud together so hard that it sticks!

It is important to point out at this stage that the earth must be moist, but not soaked, and definitely NOT dry. Dry bricks don’t bond at all (I know – I wasted half an hour making one). Wet bricks wont compress as the water has no where to go.

So, you have a frame, and you are going to fill it up? Place the frame on a base board; throw in an inch of soil – and ram ram ram! Doesn’t it feel good bashing it down! Ha ha…

Once the block is full comes the tricky bit, and I find it is useful to have an extra set of hands. One person pushes down on the block, the other pulls up on the frame, ease it a bit at a time, from all sides, or you will end up breaking the brick. Ideally you would have a frame that came apart, but this is a time consuming thing to build, and seeing as we won’t make many blocks I did not bother.

When you have managed to pry the frame off of the block (hopefully with finger nails intact!) you should be left with a rather heavy, compact pile of square mud! Now, make another 9!

Leave them for a day or a week on a board, to dry out. Try not to let them get wet, and try to let them “bake” in the sun. If you are too impatient to wait use them immediately in your construction!

Once you have a collection of blocks you can begin to position them around the base that you made. Try and overlap joints as if it were a real brick wall. Where there are odd triangular gaps, and spaces between the edge of the hole and your earth blocks this can be filled with excess soil – and rammed “in-situ”

Hopefully your oven is taking shape now, and you can get a good idea of its size, shape, and final form? It is important that when you pack up for the day you COVER the oven / pit. The last thing you want is extensive rain damage destroying your work before you have the roof on! I used some plastic sheeting from an old estate agent advertising board.

In my next Blog – how to build the dome framework and construct the walls using an earth/straw mix!

How to build Foundations for an earth oven

Ok, so you are all tooled up, gloves donned, champing at the bit?

GREAT! Let’s get started…

First you need to dig a pit or hole that your oven will be situated in. This is not strictly essential, but you have to get the earth from somewhere don’t you? Also, by digging down it means that the walls only need to half as high than if you didn’t use the hole at all.

You will need to excavate enough soil so that half of your oven is underground. Find some boards or rigid sheeting to sheer up the edges to stop the pit collapsing, and then remove the soil to containers. I used spare recycling boxes and plastic bags (double lined).

How to build an earth oven

Hello, and welcome to the first Web log!

My garden is a small inner city patch measuring only 7 metres long by 5 metres wide. So you may be surprised to hear I am building an earth oven! Over the course of the next few Blogs I will be documenting how I went about it, what tools and materials are required, the problems I occurred, and how to actually construct an earth oven in your own garden, no matter where you live!

So, firstly, why build an earth oven!?

“It’s the summer; your mates are round for a couple of chilled Buds, or a glass of rose. The BBQ is lit and everyone is sitting round listening to some Lilly Allen or Jack Johnson”

Wait! STOP THERE!

Imagine you were all sat round an EARTH OVEN, hot pot on the go, potatoes wrapped in foil at the back, burgers grilling over the smoke, sweet corn to the edges, and a block of cheese smoking over the chimney! Small pot of tea to the side, bread buns baking, and herbs in small brown packets drying on the top!

Wow, what a sustainable and beautiful way to cook, and your friends will be impressed too.

It’s back to basics folks…

This will be food at its best; anyone who has been camping knows that food tastes better when eaten outside. Anyone that’s cooked on an open log fire knows it tastes even better with that smoky woody flavour! Now imagine it was cooked in an earth oven with a log fire, AND it was all made from scratch by your own bare hands!

This is what living is really all about.

Ok, so you want to get on and make one! Of course you do! But what do you need and how much will it cost?

“Wait there!” you here me cry… “COST!? It won’t COST anything!” – Part of the principal of earth building is that it is 100% sustainable, and should be “self sufficient”. Meaning that all of the materials come from the land, and return to the land. Also, if you are going to spend a fortune on it, you may as well buy a stainless steel BBQ that lasts for a fifteen years!

This brings me to my second point – don’t expect your earth oven to last longer than ONE English summer! If you live in a dry country, a desert, or maybe part of the world where rain is infrequent then hey it could last forever – but only with good, REGULAR maintenance. In England, London, I’m expecting this to be a one month construction period and a 4 month life time!

Right, so back to the original question, what materials and tools do you need?

* Shovel or spade;

* Scrap timber (old fence panels / scrap chipboard furniture / kitchen units / old shelving / fruit boxes from a market / bed slats / fence posts / logs / branches – anything!);

* Bricks (10 – 20 depending on the base / foundation size of your oven);

* Hammer and a handful of nails;

* Plastic / timber boxes (the type you use for moving home or recycling) or plastic bags (thick garden ones, or double up shopping bags);

* Oven gloves or tea towel to handle hot pots and trays from the oven;

* Corrugated card / plastic tube to use as the formwork for the chimney;

* Iron pot (or any pot made of metal only) – no plastic handles etc – it could melt in the heat!

* Broom / stiff brush to clean out the ashes from last nights fire;

* Metal oven tray (to bake bread on) – without an enamel or non-stick coating, it could burn off in the heat;

* Old copper / metal pipe.

Ok, so that’s it for now. Seems like quite a list doesn’t it, but don’t let that put you off – to get started all you need is a spade and some timber to shear up the edges of the hole you are about to dig!

Now that you are eager to get digging, who doesn’t want a bread oven for free! Check back for my next Blog entry for details of the groundwork and “foundations”!