STAGE 3 – Bagging and Beyond!

Bagging from the floor level to the beam is more technical because it it includes doors and windows. -Its at this point that door and window openings are inserted and these can be in any desirable shape for instance round, square or even an arch. The principle of laying the earth bags continues the same way as outlined in Stage 2 (above).

A tip we learnt was spending time pre-bagging as a gang and then focusing on laying the bags and tamping them down properly.

Square windows are the most straightforward to construct, and don’t really require formwork if the tamping is done properly.

Round windows are more complex, and should be planned ahead of time. We learned this when we tried to turn a square window into a round window (but it still worked – earthbag construction is very forgiving!).

A WORD ON TAMPING…

Next to getting the volume exactly the same for each bag, tamping is perhaps the most important activity that ensures structural integrity.

We used two types of tampers, vertical tamper that is thrust down flat on the bags and a cricket bat shaped tamper for the sides – the latter being an innovation of the labourers.

STAGE 2 – Bagging up to grade…and beyond

We felt that the plinth wall (i.e. this is the wall below the ground level) was probably a lot more important than a lot of the reading/literature suggests, especially if it’s in a tropical area prone to heavy rainfall. These first two or three courses act as a barrier to water which may up-rise and destroy the wall, and thus the structure.

The first two courses of the plinth were laid with gravel packed in the bag. We double-bagged so as to give plinth wall additional strength. After these two courses, we used one course of sand-filled bags to where the floor level would be. From this point we switched to predominantly earth bags. It’s important to remember that when laying the bag, barbed wire should be used by placing it on the first course laid down; this is laid in two rows/lines with a spacing of approximately 150mm. The barbed wire is laid in order to provide a bond between alternate courses.

The courses up to 500mm above grade were encased chicken mesh in order to provide proper bonding of plaster for the cement stucco splashback.

It is ABSOLUTELY CRITICAL that a system is used to make sure that all bags have the same volume. We achieved this by knocking the bottom out of a 15-litre bucket and filling it up twice for each and every bag.

When laying the bag over a barbed wire section, one has to use a metal slider to enable the bag be placed in a proper position. Bags should be tightly placed with minimal gaps between the bags (NB. this is more difficult with a round wall). The bag is then tamped with the tamping rod and then the slider is swiftly removed.

STAGE 1 – Laying a foundation

This stage is the most important. If this is not done properly, the risks are subsidence, structural defects emerging post-construction, and erosion.

We dug a 800mm deep trench approximately 500mm wide (NB. the hand-drawn diagrams mention 6ft, but this is completely over the top). This trench should be slightly wider than a bag in order to give enough work space. The depth of the trench depends on the soil structure, which in our case was clayey soil; we probably went a bit overboard, but we wanted to lay gravel for drainage and be able to comfortably fit three bags up to grade (i.e. ground level).

We neglected to take any photographs of this stage, but it’s hardly rocket science (and the hand-drawn pictures are pretty self-explanatory anyway). Just dig a ditch, make sure it’s level, and ensure you have adequate drainage by using lots gravel.

Getting Started - Late March 2011

In Uganda, a meeting hall with open windows and doors is known by many names and dialects; tukulu (Ngakarimojong), and ot aperu (Luo) to name a few. This is an ancient, iconic structure, usually constructed in a round shape, but it can be shaped differently. The purpose and ambience of the building is more important than its shape.

In Uganda, the International Organization for Migration came up with the idea of using environmentally-friendly construction methods that use locally available materials.

(Kindly note most translated terms are in Luo)

The materials we allowed ourselves to use included as follows:

Earth (lobo);

Polypropylene bags (kicaa), exactly the same type used for packaging food-aid in Uganda - 26KG type - they're locally available (!);

Clay soil (lobo agulu);

Gravel (kotokoto);

Sand (kweyo);

Grass (lum);

Poles (kwori);

Sisal cord (tol);

Bamboo strip (tadi); and

Dung (cyet dyang).

Other materials not locally available included as follows:

Barbed wire (chengenge);

Cement (cementi);

Lime;

Timber (bao);

Twisted rebar (adit);

Chicken mesh;

Stirrups;

Binding wire; and

Nylon cord.

Equipment / tools required include as follows:

Hammers (nyono);

Wheelbarrow (gadi gadi);

Tampers;

Metal sliders;

Nails (cumaa);

Saw;

Snips;

Pliers;

Pail/bucket (baket);

Pick axe;

Hoes (kweri);

Spade (atok);

Needles (libira lakwo kicaa); and

Axe (lato).

Doing a simple test of the methods and tools is a really handy way of avoiding high costs later on when you are constructing something more ambitious. We gained invaluable lessons through the construction of a rudimentary fuel bunker. Partly because this  bunker was constructed in haste, it was what we in the aid industry call a ‘lesson learned’. The bunker had two key flaws. Foremost of these was the fact that the bags were not filled with exactly the same volume of earth; this led to lumpy, uneven walls and in a larger structure would probably lead to structural defects. The second and lesser problem, was the roof design, which we constructed from reinforced  concrete; this caused irreparable sagging rendering access difficult. At any rate, we would recommend people building a small structure before embarking on something larger and more resource-intensive.

Last but not least: READ UP!

There’s quite a few good sites online with resources on earthbag construction references. The ones we relied on include as follows:

“Earthbags!" by Madhavi Kapur Foundation's  available at http://www.mkf.in/pdfs/earthbags-english.pdf

and

"Earthbag Building in the Humid Tropics: Simple Structures" by Patti Stouter available at http://www.earthbagbuilding.com/resources.htm

NEXT: The Foundation...