Cob Green Building

Cob Green Building materials are so natural they couldn't be any greener could they, but are they really a load of old cobblers for any modern Eco Friendly green home improvement project!

Building homes from an earth based material is a very old technique which is also unbelievably labor intensive and very time consuming.

Building a home from unfired earth is a skill that is largely lost and forgotten in the modern day building trade... but now and again someone buys a really old home and finds that it is a protected building, perhaps both inside and out - and must be improved sympathetically in the old style that it was built originally.

Now and again someone decides to build a home in the country in the old way so that the building fits in well with other houses in the area and that it also enjoys the same benefits as the older homes, being nice and cool in summer and warm in the winter with nice thick natural walls to maintain indoor temperature.

In today's build it is always essential to check all plans with your local building office to make sure that your proposed build or extension or home improvement comes up to building code in your part of the world... (as always please remember that building codes are there to set reasonable minimum limits - that something should be at least 'such and such' thick/high/wide - usually it's better to go bigger and stronger and safer - enough said, back to cob green building.)


What is Cob Green Building Material

Now a lot of people when they think of Cob Green Building Material, think of waste from animal and the such but actually, even though some of that may well have been included, cob was fundamentally made of clay or mud, sand or whatever mixture that made up the ground local to the building site... together with lots of straw and blended with plenty of water.

This immediately tells us that Cob as a building material has just about zero energy spent on getting it to the work site, unless you count digging up pieces and taking them to be squashed under the horses hoofs! yup! that's how they did it but I will go into more details in a second.

So, the best earth green building material or Cob, is made up of clay and in those places where clay was not so easily available, they mixed the mud clay with a bit of chalk and what ever road grit was around.


Making Cob Green Building Material

Wherever Clay was locally found it was dug up and transported in a horse and cart to the building site in big lumps - the same for chalk if chalk is also used in the mix.

And there beside the building site the lumps were broken up and then watered and once the pieces were reasonably small... big horses were walked over the remaining lumps to break up the final pieces while someone forked short straw onto the mix and another kept it well watered.

The easiest way to imagine this human and horse cement mixer is to see all the lumps of clay and chalk and grit piled up in a big circle and see the men with forks breaking up the bigger lumps and then the final lumps squashed by a couple of big horses crossing over the circle while men make sure the larger lumps get under big hoofs while others throw on broken straw and others adding water from wooden pails or buckets.

Making Cob green building materials graphic


Keep in mind that they needed an awful lot of cob to make a house, even a one room abode that had one brick chimney stack as one gable end. Often if the natural cob making materials were dug up from land near the home they later turned the hole in the ground into a garden pond, nice idea.

The cob clay was mixed up well and kept surprisingly wet and that is how they made yesteryear cement!


Using Cob Green Building Material

Cob green building material was rarely put directly onto the floor.

In traditional cob construction, first a foundation wall of stones going from the ground up was built which dictated the outer and inner walls of the structure and onto this the cob was forked on (as the foundation wall was only about a foot high) and later tossed up in wet lumps to a skilled cob wall maker as the height of the wall grew.

What was incredibly time consuming was that you could only layer and pack a certain amount of the cob clay mud onto a wall before you had to leave it to dry and set before you could start building up again - and of course all this was at the mercy of the weather that could stop a build or ruin a build at any time before the roof was on.

While the cob green building material wall is left to dry for a few days, during pauses in earth walling, the builders were probably taking the opportunity to haul over more lumps of clay and chalk and ground grit to make up more of cob specific to their area, while others, known as "daubers" would be smoothing the walls and clay filling in any rough bits where ever possible to keep the construction a clean build.

While the walls of the cob green building rose, empty spaces had to be left for windows and doors and beautiful cast iron glass filled frames set in place before the build carried on up.


Cob Green Building takes time

Building with Clay in the old way was done during the spring, summer and if necessary early autumn months when days were long and filled with sunshine and the dry warm weather that helped get the cob dry and set.

But building took time and this was mainly because work was done in spare time - and as working hours for laborers was largely from dawn till dusk, spare time was very scarce.

Communities would sometimes come together to get a build on its way before the weather changed and this was especially important in the case of earth built homes.

Many cob built homes were built one room at a time, expanding the structure during the summer months over many years and this accounts for the sometimes strange and intriguing layout of rooms that can be found in these wonderful older constructions.

The most important thing to remember about Cob built structures is that they can last for hundreds of years, and they have done... as long as the cob walls are protected by a substantial overhanging roof to help keep the worst of the rain off the walls.

A Cob build wall that has started to decay through damp smells pretty bad and swells which then allows even more water penetration. It was vital to keep the outer surface of the wall coated in lime wash and repainted layer upon layer year after year.

But if the side of a home was particularly vulnerable because it was continually hit by slanted driving rain in a windy location, then the surface could be clad in slate tiles... just like the roof... to give extra protection from the elements.


Roofing a Cob Green Building

Original roofing known as 'Coping' for a Cob Green Building, was thatch. Now thatch, depending on the type used, has to be replaced every so many years (we will go into thatch in another article) so you will not see original thatch hundreds of years old anywhere.

What is very nice to see are those lovely old cob built buildings that still have the original style of thatch roofing and that were not changed years ago for materials less desirable like the dreaded asbestos.

If you plan to buy a beautiful old cob built cottage beware! you should have the roof checked for asbestos - (hard to imagine two different materials like thatch and asbestos being more different, they are just worlds apart) asbestos has to be professionally removed before your home can be re-framed and re-roofed with natural thatch. Very nasty stuff that asbestos and quite an expensive fix!

As I said before roofing, or coping on a cob building had an extra long overhand to protect the building and these now the most photographed earth built architecture that is used on chocolate biscuit boxes.

The natural thatch roof was fixed in place as soon as possible to make sure that the cob wall construction did not suffer from water damage if the good weather turned.


Living in a Cob Green Building

The first time that anyone wrote about a Cob building was way back in the early 1600's, and many homes built in the early 1800's are still enjoyed as family homes today.

Many were modernized in the mid 1900's, especially between the 50's and 70's when it was popular to take the character out of the building and replace the windows and doors.

Living in a Cob home meant thick walls around 3 feet thick that helped make sure that you were nice and cool inside in the summer and that the house maintained heat well throughout the winter.

They were quite dark inside because windows were fairly small and the original iron frames meant lots of small panes of glass but... they made up for it in lots of small warm, cosy rooms.

As the electric age emerged is was especially tricky in an earth built home to sympathetically install all the necessary wiring for modern living but cables were often boxed in with wood like a roof beam.


Modern Cob Green Building

Long gone are the days when there was shame in a cob construction, when a home facing onto a public street might have been build of stone just to try to hide the fact that the rest was cob built.

Homes are being built into earth and earth built homes have a chance of being revived for the first time in nearly two hundred years.

New designs for modern cob green building homes should include plenty of glass windows and doors to provide lots of natural light to the interior - and should incorporate as many of the modern green building techniques as possible together with wind and solar energy and ground heat and water collection.

If you have the right plans and the time and the money and the right building site, working on an earth green building through Cob Green Building could be a dream home come true.


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