Lets unravel the Rammed Earth Wall, an innovative material and an interesting technique of construction…a technique used from time in memorial.
Firstly, let me introduce myself… I am Shankar, shortly SAN (and I like to be called this way). I have been with the Shilpa team for 1.5 yrs. My design team and I work on various projects on diverse discipline including architecture, interior, landscape and master planning.
I got a wonderful opportunity to research this new material and construction technology for one of our projects. Honestly, I never imagined I will blog on this as it is my first blogging attempt! Here we go….
REW: Background Information
Rammed Earth Wall aka REW….. was a completely new term for me at the start of this process. Well, we have all heard of mud walls, stone walls, brick walls and other kind of block walls. But what is this new term? Rammed earth… I was very concerned in dealing with it initially… but my curiosity has been piqued and I wanted to research this material further. I started by understanding, how it is constructed, cured and finished. At first, I thought that this material will not stick around much longer in the project and will go away as quickly as it came on board, as this is the case in several new techniques that are reviewed and condemned.
It was soon time for the construction of the sample wall to study the structural compatibility with conventional construction. I got a chance (which I was waiting for) to see a mock-up of a REW. I was thrilled to actually experience this exciting new addition that I knew I had to deal with through the life of this project.
Case study 1: Sample Wall @ Project Site
The day has come… It was in the month of January a couple of days before pongal. We left the city in the morning and after a long drive, we reached our destination: the Site @ Marakanam –ECR. Anxiously the team approached the sample area. … WOW!! This was the first reaction from everyone as we first encountered it.
It was very natural, fresh, bright, and yet was stately in its mass. The wall looked solid!
The contractor then began to describe the REW characteristics. Technical Information are as follows:
1) Rammed earth wall is a well compacted, consolidated wall with a compressive strength 2 times than that of a standard brick wall.
2) The foundation requires an excavation of 5 feet depth and a standard footing built with PCC bed and conventional brickwork up-to the height of the Plinth beam.
3) Once they reach the plinth beam level, the shuttering and form work process starts.
4) Standard sizes of plywood shuttering planks (say 8’ x 4’) will be framed on either side of the plinth beam thereby extruding the wall.
5) The Composite Mixture consists of Clay: Sand: Cement mixed in the proportion of 1:5:8.
6) A REW requires a minimum of 21 days curing period.
7) The height achieved by REW is normally 10 feet and a further height can be achieved by increasing the thickness of the wall.
8) REW must be built first prior to any other kind of additions since ramming the sand causes vibrations.
9) Steel rods are inserted at 2 feet intervals across the wall for better bonding and strength which are removed after curing.
10) The color of the wall depends on the color of the Sand that is mixed in to the Composite Mixture.
11) Various colors like red, white and grey REWs are possible.
12) Availability of sand must be assured across the volume requirement of the project before the commencement of work to ensure uniformity.
13) Running of services (ex: conduits, wiring etc) can also be done on a REW provided it is pre-planned. These will be embedded into the wall prior to ramming and cannot be altered at a later date. This is one of the limitations of REW.
14) The REW is termite proof, spill proof as the composite mixture is pre-treated with required additives.
15) Construction costs are slightly higher than standard brick walls
Case Study 2: Live Site
With our new knowledge on the material, we proceeded to another site which was in progress. The purpose was to understand how REW’s are constructed and integrated into other conventional forms of construction. Unfortunately, the REW has been completed and we could not see a live-site where ramming of the earth was in progress. Conventional clay burnt brick work (Kandi Kal – locally) is in progress at this site. The project was a small farm house. The contractor pointed that REW’s were not load bearing structures instead RCC beams transferred loads over to a row of rafters and purlins covering the roof in a vernacular style (see image). Other traditional materials and fixtures were used on this cottage including tiled sloped roofs and wood decorative columns. The color of the REW was cool and appealing as it exuded a look that was natural, bright and vernacular. We thought the walls looked neat, clean and massive.
Case Study 3: An old house with REW.
The last case study was a house that had stood the test of time for about 15 years. It is a G+1 building completely constructed with REW’s. The slabs are cast in RCC, while the rest of the shell is REW. This was a load bearing structure and we completed our study of the material and its extensive usage as a structural element. However, through time the REW had been painted over with primary colors. The natural look of the REW is lost but structurally and technically this was a great example of the weathering qualities and sturdiness of the material. The contractor took pride in this case study as a showcase of the strength and durability of this technology.
To sum up with all the case studies, the sample wall for our project, a live construction site and an existing house, we have understood that Rammed Earth is a wonderful load bearing material which has great aesthetics, strength, durability and color.
Have a nice day!