Tuesday, March 10, 2009

Rammed Earth Construction Part I - Creating the Foundation
February 27, 2009

(For a list of all of the Rammed Earth Construction blog entries, go to the Index Page.)

The foundation construction that Martin and Anna developed is the key to durability of the mud structures. A concrete and brick foundation with a vapor barrier prevents the moisture from the ground from seeping into the mud walls, weakening them from the bottom. Traditional Bangladeshi mud structures build the mud walls directly on the ground. The monsoon rains and annual flooding severely weaken the lower portions of the walls making them susceptible to cracking, collapse, and pest penetration. The brick foundation, however, goes two feet down into the ground and two feet above the ground, raising the walls above the flood plain. A vapor barrier keeps the lower portion of the walls dry. There are mud buildings in Europe that are still standing after over a hundred years.

To create the foundation:
  • Dig a foundation hole
  • Build a four foot high course of bricks with cement mortar. The walls should be approximately two feet thick.
  • Plaster the walls with a layer of cement
  • Put a vapor barrier down on top of the brick foundation.
  • On top of the vapor barrier you need to put a thin (half cm) layer of clay plastering; this helps the rammed earth stick better to the foundation. (See Part II - Mixing the Mud for clay plaster recipe.)
Vapor barriers can be made from:
  • Polythene sheet (use a double layer and make sure there are no holes in it),
  • Coat of bitumen,
  • Layer of ferro cement (steel mesh with a coating of cement over it; this is what we used on our project)

Building Foundation
The foundation had been prepared for us when we arrived. It is constructed of bricks with cement mortar and a thin plastering of cement on the outside. The top has a layer of ferro cement.


Detail of Ferro Cement
In this photo you can see the steel mesh of the ferro cement. The craftsmanship of the foundation was quite poor; if the foundation was properly constructed you should not be able to see the mesh! Exposed mesh like this will eventually rust and create many problems down the road.


Illustration of the Foundation Construction
An illustration I did of the different parts of the foundation.


This is Part 1 in a 6 part blog series. For a list of all blog entries on rammed earth construction, please see the index page.

1 Comments:

At Thursday, October 29, 2009 7:17:00 PM, Blogger Ingrid Lyndon said...

Very interesting!

 

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