Rammed Earth Home
A mystery I am reading (Exit Wounds by J. A. Jance) has mentioned over and over that the sheriff lives in a new “rammed-earth home” with “thick walls and high ceilings”. It is “pleasantly cool”, despite the over 100 degree weather. I guessed “rammed-earth” was another name for an adobe house; the mystery is set in southern Arizona. About the fifth time the house was mentioned, I googled it.
Rammed earth buildings can look like an adobe, but adobe is different.
Adobe is mud brick. Bricks, around 10” x 14”, are made with straw and dirt mixed with water. The mixture is pressed into a form or frame. After they air dry, they are stacked, using mud as mortar. Then the outside is smoothed with more mud. When it’s done right, the house is durable and comfortable.
Rammed earth building is completely different. The mud is molded in place. A frame or form is built where the wall will be. The mud mixture is pressed and pounded into the form.
Rammed earth building is not new. This cottage near Guildford, Surrey in South East England was built of rammed earth in 1919. It doesn’t look anything like a southwestern adobe house.
Cottage Building in Cob, Pisé, Chalk & Clay – A Renaissance by Clough Williams-Ellis was written in 1919. It has techniques and house plans to build traditional style houses using rammed earth techniques.
“The construction of walls determined upon was that known as “Pisé de terre” consisting of earth walls some 18 in to 24 in thick, which owe their solidity to a simple process of ramming between wooden casings previously placed in position on both sides. These walls are built in stages of some 3 ft. in height, the wood casing being raised at intervals as required. The frames for doors and windows are placed in position at the right time, and anchored into the walls by means of long hoop iron ties. These walls, when completed, give a surface almost as hard as burnt brick, but the external angles present a slight point of weakness, as from their exposure they would be naturally inclined to chip away in cases of rough usage. In order to overcome this it was arranged that irregular brick quoins should be embedded in the angles all the way up as the work proceeded.”
Cottage Building in Cob, Pisé, Chalk & Clay – A Renaissance by Clough Williams-Ellis
There are a lot of rammed earth or pise de terre houses around. They are really durable. Rammed earth houses from the 1800s are still standing today.
Rammed Earth construction is having a real renaissance with new techniques like using cement to stabilize the mud mixture, metal forms, pneumatic tampers to compact the earth and building the walls on conventional footings or slabs.
This photo shows how thick the walls are. The form is left in place only until the pounded earth is stable. Just like the Clough Williams-Ellis book says, “These walls are built in stages of some 3 ft. in height, the wood casing being raised at intervals as required.” You can also see holes for windows and doors are left.
The man is compacting the earth softened earth to make it dense and durable. It is pounded until it compacts to about half its original volume. “…walls some 18 in to 24 in thick, which owe their solidity to a simple process of ramming between wooden casings previously placed in position on both sides.” Clough Williams-Ellis book
The Eden Project, an “educational charity, social enterprise and visitor attraction” promoting sustainability has some rammed earth walls.
A rammed earth wall forming part of the entrance building to the Eden Project in Cornwall, England. Many aspects of the Eden Project champion environmental sustainability and due to their thermal mass, rammed earth walls fit in with these environmental aspirations.
After five year, the corner of the wall already shows surface damage. Although given the thickness of the walls this probably isn’t too significant. The damage is partly down to lack of testing and education about building with earth on the builders side.
This is the wall. You can make a virtual visit using Google Street View.
There are plenty of books on Amazon with photos and ideas for modern and traditional rammed earth houses.
Essential Rammed Earth Construction by Tim J. Krahn P. Eng is a Complete Step-by-Step Guide. It has theory and technicalities with lots of photos, diagrams and step-by-step instructions.