Rammed earth walls: natural and sustainable living

 

‘Rammed earth’ is a technique for constructing foundations, floors and walls from natural raw materials such as earth, chalk, lime or gravel. With the lowest enviromental impact of all building techniques currently used in the commercial construction industry, rammed earth is receiving growing attention and becoming more and more popular with architects, builders and clients alike. In this short post, we tell you a little more about the technique.

Rammed earth walls RISE Design Studio architect west london

Mixing it up

Rammed earth walls are made by ‘ramming’ a mixture of materials into place between flat, temporary panels called ‘formwork’. The panels are normally made of wood or plywood and they are clamped around the earth to make sure it doesn’t bulge when compressed. The materials rammed into the formwork generally include gravel, sand, silt and a small amount of clay.  An additive like lime, cement of asphalt is often added to make it extra strong.

The mixture is compressed inside the formwork by a mechanical ram and compacted to approximately 50% of its original height. The compression takes place in stages, usually in depths of 10cm to 25cm, and this is repeated until the top of the formwork is reached. This is the part of the process that results in the beautiful layers sometimes seen in rammed earth walls.

After the wall has been completed, the formwork is removed and a surface texture can be applied, e.g. by wire brushing or carving. The wall is normally too hard to work on after about one hour. As the walls dry and harden (ideally in warm weather), the compression strength of the rammed earth increases to a maximum of 4.3MPa (620 psi). This is less than concrete but sufficiently strong for domestic buildings.

Environmentally-friendly

Cured rammed earth has a high thermal mass. This means that it absorbs heat during the day and releases it at night, which reduces heating and cooling costs. Environmental impacts are also kept low if the amount of processing of rammed earth materials is kept to a minimum (i.e. artificial additives) and material is sourced locally where possible. Most of the energy used in the construction of rammed earth is in quarrying the raw material and transporting it to the site.

Healthy home

The composition of rammed earth allows it to absorb and release humidity from the inside of a building. This improves air quality, particularly for people who suffer from asthma. Rammed earth is also inorganic, which means that it won’t decay and does not support the growth of mould.

Back to our roots

More than 30% of the world’s population uses earth as a building material, hence this technique is not new. Properly constructed rammed earth can also last for thousands of years, demonstrated by the many ancient structures built using this technique which are still standing around the world.

It has received growing attention in recent years as the construction industry and its customers have a growing sense of the need for environmentally friendly and sustainable building practices. Not only does the technique offer opportunities for carbon-neutral building projects, the technique can be employed in a wide range of climatic conditions and for developing housing that would otherwise be constrained due to expensive construction techniques.

It is a technique that we have been exploring at RISE Design Studio, particularly in our drive to use local, sustainably-sourced building materials.

History of plywood and its present day use

 

We have recently completed several projects that have used plywood as a feature material. Plywood is made by gluing together thin sheets of wood (‘veneers’), with the grain of each sheet running in a different direction. The result is a material that is stronger and more flexible than solid wood. The history of plywood has been described as “a history of the modern world” – plywood started to be used on an industrial scale in the 1850s. In this post, we take a quick journey through that history and reflect on the uses of plywood in architecture and design today.

Plywood kitchen design self build london

The art of moulded plywood

In the mid to late 1800s, plywood was most commonly used in moulded form and was used mainly in furniture design. The ‘Belter Chair’ was most famous at this time, as the technique of moulding plywood to make this high-backed chair increased manufacturing speeds and reduced production costs.

The Finnish architect, Alvar Aalto, was also one of the pioneers in curved plywood furniture, enabling large-scale manufacture of chairs and other furniture designs that were exported across the world in the early 1900s.

American designers Charles and Ray Eames also experimented with moulded plywood during the Second World War, developing a lightweight, stackable plywood leg splint for the armed forces. The Eames Chair, also in moulded plywood, was one of the most influential chairs of the mid to late 20th century and continues to be adapted and imitated by designers around the world.

Ray Eames - stackable plywood leg splint for the armed forces

Plywood transportation

Cars, trains, boats and planes are perhaps not the first things to spring to mind when thinking about plywood. However, during the 1800s, designers and engineers explored ways to deal with increasingly crowded streets. An elevated railway, made entirely as a moulded plywood tube was suggested in 1867 in New York, and in the early 1900s, a German company extolled the virtues of using moulded and flat plywood for the body of their affordable family cars.

Perhaps more familiar would be the use of moulded plywood in canoes. From 1917, the US firm Haskell manufactured moulded plywood canoes and sold them in large numbers across the world. The boats were very light and very strong.

The firm went on to design aeroplanes using plywood and this was perhaps the most technologically significant phase of the material’s history. Between 1910 and 1945, its strength and lightness allows innovative new planes that ‘revolutionised the nature of flight’. Moulded plywood shells (the ‘monocoque’) were strong enough to be self-supporting (they didn’t need any internal structure) and became standard in future aeroplane design.

Plywood at home

In the 1930s, plywood was perfectly suited in the construction of prefabricated houses for people on low incomes during the Great Depression. With the invention of synthetic glues at the same time, it was possible for plywood manufacturers to produce waterproof plywood for external use.

Plywood in the digital age

Today, plywood is one of the most common materials of the digital age. It is possible for designers to share plywood projects via digital cutting files, or videos and other images posted online. It continues to be widely used in residential and commercial architecture projects, and its ‘clean’ finish is appreciated by a growing market interested in using sustainable materials that are sourced responsibly.

Different types of metal casting

 

We design bespoke lighting for our clients and light fittings can be made from a range of metals, including brazed copper, brass, black mild steel and light mild steel. Currently, we are researching door handle design and manufacture (small scale – batches of ten or so) via casting metals in a foundry – liquid metal is poured into a mold that contains a hollow space of the required design, and is then left to cool and solidify – the solidified part is called a ‘casting’. In this short post, we explain the different types of metal casting and provide some brief information about foundries (factories that produce metal castings) in the UK.

Bespoke brass door handles london.png

How does casting work?

The first stage of metal casting is to make a mold into the desired shape. A mold can be open or closed: in an open mold, the molten metal is poured directly into the mold cavity and the material is exposed to the air, like a cup. Closed molds are more common: the molten material flows into the mold via a short entrance cavity and the mold is closed off from the air. Metal is melted in a furnace before being poured into the mold, normally by automatic pouring machines. After being left to solidify, the metal component is removed from the mold, degated (any excess material is removed) and cleaned. The product is then ‘finished’, which usually involves grinding, sanding or machining to ensure the desired finish is achieved.

Some different types of casting

Molds can be expendable or permanent: an expendable mold is made of sand, plaster, or similar, and can only be used to produce one metal casting as the mold must be destroyed to remove the casting. A permanent mold can be used to make many castings as it is usually made of metal or a refractory ceramic, with sections that can open or close to allow the casting to be removed.

There are several different types of expendable mold casting. Sand casting is the most common, as almost all casting metals can be produced using this method. Sand castings can be any size and used to make a wide range of products, with another advantage being that sand is inexpensive. Plaster mold casting is a similar process to sand casting, with plaster of Paris used instead of sand to make the mold. Other types of expendable mold casting include: ceramic mold casting (allows materials to be cast at much higher temperatures); shell mold casting (particularly suited to steel castings); vacuum casting (also known as the V process, which uses sand with no moisture with the internal cavity of the mold held in shape using a vacuum); expanded polystyrene casting (a sand mold is packed around a polystyrene pattern); and investment casting (a wax pattern is coated with refractory ceramic material).

When working with permanent molds, ‘basic permanent mold casting’ is a term that describes all types of permanent molds. Sections of the mold are normally made from metal blocks that fit together, allowing them to be opened and closed easily and with accuracy. Although making the mold can be expensive, it may be used tens of thousands of times, making it suitable for products such as kitchenware.

Metal casting foundries in the UK

The majority of foundies in the UK are members of the Cast Metals Federation (CMF), the professional body representing and promoting the UK casting industry as a whole. The CMF website has a directory of foundries and suppliers.

More information about our recently completed bespoke lighting designs (door handle designs to be completed en breve): El Montovano Pendant; El Kiazim Wall Light; Christie Pendant Light.

Exploring Chailey Brick Factory

 

We recently attended a CPD tour organised by RIBA to the Ibstock brick factory in Chailey, near Lewes in Sussex. It was fascinating to see process of traditional stock brick manufacturing in one of the last remaining clamp-firing factories in Europe. We highly recommend a trip to the factory if you’re looking to source traditional stock bricks. This short post tells you a bit more about what we learned on our visit.

chailey-bricks

History

Clay products have been manufactured in Chailey for over 300 years, making it one of the oldest factories still in production in the UK. Its product range has changed over time and it now produces high quality, clamp-fired stock bricks and pavers with a range of colours and textures which give a unique charm. Bricks are known for being made in Chailey since the early 17th century. The current factory was built in 1946 in order to take advantage of modern production processes and the post-war building boom. The current owner, Ibstock Brick, acquired the site in 1996.

Making the bricks

At Chailey, weald clay is extracted from an onsite quarry behind the factory during the summer months. There are three different seams of clay in the quarry, all with different drying and firing characteristics. Clay is dug from a stockpile each day and fed into the factory, delivering a set amount of clay each hour. Clay is mixed with sand and pulverised fly ash, which help with the drying process, and with a blend of coke breezes, which is the fuel that fires the bricks. All the material is fed into a wet pan, where it is mixed and ground together and water is added. The material is forced through grids in the floor of the wet pan and onto a conveyor, after which it falls between two counter-rotating drums, with a gap of only 3mm between them. This is so that a small but consistent grade size is achieved.

The material is then mixed in a double-shafted mixer where two shafts churn the mix to ensure and smooth and workable consistency. The mix is then taken to a kettle where it is stored before being turned into bricks in a molding machine which is capable of making 12,000 bricks per hour. The excess clay is struck off before a palette is dropped onto the bottom of the bricks. Bricks are piled in stillages which are then put into the driers, where the bricks are dried over a 23 hour period. There are five dryers and each one holds 24,192 bricks. The temperature in the driers is slowly increased up to 110 degrees and approximately 17 tonnes of water is removed from the bricks.

The clamp

A clamp is ‘a carefully constructed stack of bricks’ in a large shed similar to a cowshed. Before going to the clamp, the dried bricks are inspected for defects and stacked into piles of 780 bricks (weighing 1.8 tonnes). These bricks are then laid on the floor of the clamp by hand by a setting team. Fire holes are built into the clamp before all the bricks are laid on top and the clamp is then covered in refractory insulation bricks and casing bricks which help to insulate the clamp during the firing process. Each clamp holds between 750,000 and 800,000 bricks and takes three weeks to build.

brick-clamp

Gas burners are used to ignite the fuel which was mixed into the body of the bricks during the clay preparation process. The bricks fire at over 1000 degrees centigrade and only start to cool down when all of the fuel has burnt out. The entire firing cycle takes three weeks. When the bricks have cooled sufficiently, the bricks are packed up by hand onto pallets by an eight man team. There is a strict sorting code and the bricks are sorted according to their quality and colour and then hand sorted into packs of 370 bricks. It takes approximately two weeks for the team to pack up a clamp.

clamp-full

The bricks

Chailey manufactures its range of distinctive bricks in both 65mm and 50 mm sizes and any of the bricks can be blended to create products to match up to existing brick work. Or, bespoke blends of bricks can be created. You can read more about the bricks made at Chailey on the Ibstock Brick website.