Cool Earth Project: Hinterland House

Formwork Shapes

Most formwork used, whether horizontal or vertical, is designed on the principle of straightened panels which yeild flat surfaces. Research work has been carried out to find ways of getting away from the limitations this imposes.

Plane and perpendicular surfaces

This is the most used set-up, being used as often in traditional rammed earth construction as in modern rammed earth buildings regardless of the type of formwork used. The principle is simple and does not give rise to any complex problems.

Batter

This formwork can be used to produce plane perpendicular or plane inclined surfaces otherwise known as the butter of the wall. The slope is toward the centre of the wall and progresses as the wall rises. Only the outer face or both faces of the wall can be battered, and simple wooden packing pieces or wedges known as 'batter fixes' can be used to effect the design. The batter lightens the mass of the wall in proportion to its rise.

Curved Surfaces

With certain types of formwork it is possible to make curved surfaces. This can be a matter of curving walls at corners or the construction of buildings with curved walls.

Composite face design

A formwork system using modular panels makes it possible to fashion surfaces composed of small vertical faces. The concept is suited to the production of diverse shapes including posts of geometrically variable cross-section.

Moving Formwork

Gantry formwork

This technique is best suited to the construction of piers or wall sections.the formwork is light, consisting of simple planks, plywood panels or even billets which are kept in position by wooden supports driven into the ground and secured at the top.

Formwork with rollers
the concept of a mobile travelling form, based on the use of rollers is suitable for the construction of straight walls, but requires stationary formwork for bays, corners and partition walls

Sliding formwork

various attempts have been made to adapt the sliding forms used in concrete construction. up to the present time, the various realisations are laborious affairs, though they work quite well

Pulverization

rammed eart must be pulverized. this also applies to clay-like earth composed of hard lumps, to which a sandy fraction must be added. to improve this clay-like soil condition with sand, alternating the processing of the clay component with the sand in the pulverizer will result in greater quality. it is recommended to group the pulverizing, grating and mixing operations together. the mixture undergoes the following sequence of operations: transport, elevation and distribution within the formwork. the pulverizer must be a sturdy machine, able to withstand stone and sand-like soil. it must also be able to project the earth a certain distance, in order to ensure good aeration and proper premixing.

Mixing

This process is recommended when the soil requires homogenization, or when a stabilizer needs to be added. The most suitable piece of equipment for this is a concrete mixer. A motor cultivator is also known to yield good results.  

Transport

This is one of the major problems in rammed earth technology. Large quantities of earth are required in the construction process. The material must be transported horizontally from the borrowon the construction site, and must be transported vertically as well to the required level.Traditionally, workers who build with rammed earth use manual labour to carry the soil in receptacles from the borrw to the construction site. The material is then raised by ladder or scaffold to where it will be used.The same task can also be achieved in an efficient manner by means of hoists.  



Keeping the formwork in Position

Once the formwork has been set up and put in position, it must be securely fastened.

There are various ways of doing this.

Big clamps and Large holes

The clamps are solid cross-pieces as thick as a rafter and provide a support for the boards of the formwork. With this type of clamp large holes appear in the rammed earth when the forms are removed. The clamps should ideally be slightly conical so that they can easily be removed without damaging the rammed earth. Planks can be used as scaffolding if the clamps project from the boards of the formwork.

Small clamps and small holes 

This system is based on concrete formwork technology. Threaded steel rods, concrete bars or flat iron bars can be used as clamps. Only small holes will appear when the forms are removed. The bars should be thick enough so that they can support the forms and avoid shearing the rammed earth.

Without clamps or holes

Independently gripping formwork - The boards are kept in place by a tensioning device or screw-locking system or locking hydraulic jacks.

Formwork on posts - To eliminate the risk of bulging walls, care must be taken that the distance between the posts is not too great.

Formwork

There are numerous factors to be considered when dealing with formwork; the construction site, amount of labour available, excecution times, the desired result, architectural plans and the type of finish desired.

Formwork made up of small parts

Horizontally sliding formwork - This type of formwork system was developed by craftsmen and has a wide range of variations. It essentially utilises typical fastening systems such as clamps. Its advantages are; its lightness, manoeuvrability of the equipment and its adaptability.

Vertical sliding formwork - This system is perfectly suited for constructing rammed earth walls in piers. It allows for greatly accelerated erection of a structure if the formwork is carefully designed.

Integral formwork

Previous attempts at using concrete formwork technology have not been very successful. This method is graetly dependant on the architectural design, essentially on whether it features modular dimensions, full walls with independant bays and very simplistic drawings.

Integral horizontal formwork - This is in a case where a ring of formwork is moved vertically. For this system to be successful, the elements must be light and should be assembled and disassembled easily and quickly. Difficulties rise from the joints between the boards and horizontal alignment.

Integral vertical formwork - This type of formwork is mainly used in the construction of large piers, contained in formwork for their entire height. In order to facilitate ramming, only one side of the formwork is completely erected. The second is erected as the wall is constructed.

Integral - integral formwork - This is a case where the formwork for the building is set up at a single go. Projects using this type of formwork should be small and offer easy access inside the formwork.

Cool Earth Project: St. Bartholomew's Chapel

Rammed Earth is not only for domestic buildings but it can also be used in bigger community buildings.
 http://www.eartharchitecture.org/index.php?/archives/1144-Saint-Bartholomews-Chapel.html

Excavation & Extraction

Excavation can be done manually or mechanically.

Manual

The tools used here are the same tools used in agriculture, mining or road construction, so they are easily accessible. These include, picks, spades, mattocks, shovels, crowbars, rakes, etc. Manual excavation requires a lot of labour thus creating employment in the area. Another advantage is thayt since there is no carbon-dioxide emitting machinery involved, less harm is done to the eco-system.

Mechanical 

Theres is a wide range of machinery that can be used. Most of these can be easily modified to suite the conditions or even the kind of work being done. An example would be the mechanical shovel which can be fitted to be used as a loader, excavator, grab, or clamshell excavator.

Screening

It is quite important to frequently screen the earth which is going to be used in the construction. This can be done by manually removing the larger stones and for smaller stones a vibrating screen can be used. This is done until a finer, powdery grain of earth is attained.



Techniques

In the  tradition of earth construction, we can recognize several building methods, which reflect certain identities and cultures, indigenous to particular regions. There are 7 main classes of technique which are most commonly used today, including: rammed earth, adobe, straw-clay, wattle and daub, direct shaping, compressed earth blocks, and cob. The main focus of this blog, however, is on rammed earth construction.

Rammed Earth

This method of earth construction involves the compaction of earth in a formwork. In many countries, wooden forms and rammers are used. The technique makes it possible to build monolithic walls in compacted earth.

Introduction

What on earth is a blog inspired by the growing needs of the rural community. With South Africa's increasing population, the demand for basic housing and services has increased considerably. It is the government's responsibility to ensure that these basic services are provided for the poor, in the most energy efficient and cost effective way.Earth construction has been one of the most widely-used construction materials in the world. Nowadays, more than a third of all humanity lives in a home built of earth.