Rammed earth homes

Aerecura Sustainable Builders offers a pre-designed home

Rammed earth has been used as a building material for thousands of years, and Aerecura Sustainable Builders have revitalized and modernized this ancient technique to build walls for contemporary house construction. The basic method is using a hydraulic ram to compress a mixture of type “A” gravel, cement, waterproofing material and a colouring agent by about 25 per cent of its initial volume. The resulting wall is incredibly strong and is impervious to air and water. “Essentially, we’re building rock walls by using composite materials to do so. We take all those loose materials and compact them down into a solidified wall. What Nature does over thousands of years, we do in about three minutes,” said Graham Cavalier, general manager and co-founder of Aerecura Sustainable Builders. The company got its start in 2009 when Mr. Cavalier’s mother, Sylvia Cook, was looking for a way to build a sustainable home on her property near Castleton, Ontario. Her research led her to the rammed earth technique and she persuaded her son, who was in his third year of study at Queen’s University, to partner with her for this project. They built a garage that year as a proof of concept, and the following year they built the walls for her home.

The material for a rammed earth wall is laid down in layers, with each layer being compressed before material is added on top of it. This method can provide a wide array of colours and patterns that flow organically and which is not fully revealed until the wood forms come off. The wall is effectively engineered stone and will last hundreds of years. For house construction, a three-shell approach is used. There’s an outer shell of rammed earth, a middle space filled with insulation and an inner shell of rammed earth. The inner and outer shells are connected by rebar, making a solid unit structure approximately 50 centimetres thick. The outer layer protects against weather and the inner shell helps to regulate the inside temperature. Adding an insulated steel roof and triple-glazed windows makes it extremely energy efficient when it comes to heating and cooling.

Aerecura has been building custom homes since 2016, and has been building in the County since 2019, with at least five homes completed and one now in progress. Recently, they have created a plan for a three-bedroom rammed earth home. Pedro Paes was trained as an architect in Brazil and moved to Canada in 2018. He has since become a licensed home builder in Ontario, and created the plan for Aerecura’s new offering called The Petra. It’s a three-bedroom, two-bathroom home, with an open-concept kitchen, dining and living room area. “We wanted to create a building that is not only beautiful and showcases the rammed earth, but is also buildable for us. We’re making sure that we’re able to get the feel and comfort that a rammed earth home has, but making sure we keep the design as streamlined as possible,” said Mr. Cavalier. He said that a part of the design is an interior feature wall that provides thermal mass as well as acoustic separation from the sleeping area. It is designed so that the low winter sun will shine through south-facing widows and onto the feature wall, heating it up during the day. Thanks to the thermal characteristics of rammed earth, that heat will be slowly released during the night. In the summer, the insulated and overhanging roof will prevent heat build-up during the day, and the hygroscopic properties of rammed earth will help to control interior humidity. Carbon sequestering is an integral part of the build. The insulating layer between the rammed earth shells is a new type of materials derived from cornstalks left after harvest. The roof and floor insulation is made of dense-pack cellulose, derived from recycled newspaper and fibres. As the house is effectively air-tight when the windows are closed, the heating and cooling system incorporates an energy preserving air exchanger system.

Mr. Cavalier said that the initial construction costs are about 20 per cent higher than for a conventional build, but that cost will be recovered in long-term savings on energy and maintenance cost. “Maintenance and repair are about as close to zero as you can get in a home. Rammed earth walls are incredibly resilient. They will get stronger as time goes on. They are fire proof and flood proof. With a properly installed roof and windows, you’re looking at easily 50 years before you would need to maintain those aspects of the home. Passive solar heating in the winter and effective insulation in the summer will reduce energy costs,” he said. Another benefit of rammed earth construction is the availability of building materials close by, with the County builds all using gravel from C. B. Fennell. For more information about rammed earth homes and to see photographs of completed builds, please visit aerecura.ca, or send an email to Lindsey Van De Keere at info@aerecura.ca.