6. Soil Testing
A. Grading test—the soil must have a range of particle sizes from fine silts to gravel. This ensures bonding between the particles can occur giving you a strong mudbrick. If only one particle size exists it is unsuitable.

 1. Fill a straight sided bottle to one-third full of soil.
 2. Add water to two-thirds full.
 3. Cover the end of the bottle and shake vigorously until all the soil  turns to mud.
 4. Set the bottle down and allow the soil particles to settle.

B. Dispersive Clay—Place a 12 mrn diameter ball of clay into a glass of water and leave overnight. If the water is milky the clay is dispersive which will cause excessive weathering and erosion problems with the mudbricks.

C. The Wash Test—Washing your hands after you have been working the soil can reveal a lot about the soil. High clay content soils will feel soapy and are hard to wash away often leaving a stain. Silty soils feel powdery like flour but wash fairly easily Sandy soil is gritty and very easy to wash off.

D.The ShineTest—Take a sample of the soil and rub it with something hard like a piece of steel, knife or fingernail. If it has a high clay content it will shine, and is generally unsuitable for mudbrick.

7. Low Water Consumption
One advantage of a Dalrac Mud Brick press is that a lot less water is used in its operation. This means less water has to be carried or stored and further the mud bricks are less likely to crack.

 8, Pressed Mudbrick Making and Storage
The material should be left in a heap after the excavators have been around, and covered by plastic to stop the weather 'hardening' the pile again.

While it is not essential, it is often a good idea to sieve the material through a bed spring of a 1/4 inch screen, to remove the larger lumps which can cause weaknesses in the mudbricks.

You may add cement or lime, bearing in mind it will be more expensive although will produce stronger bricks, just to cover up any errors in your judgement about the suitability of the material, and now is the time to do it. Here a concrete mixer makes life very easy. But costs will be higher.

The raw soil is added to the mixer, along with the measured amount of cement (up to 5%), say a small tin, depending on your quantities, and rumbled. If you want to use lime, use up to 10%.

The moisture content should be such that a handful of material, when squeezed, should hold its shape not ooze through your fingers like toothpaste or crumble like dry sand.

The machine is loaded and the brick pressed and stacked if not being used immediately. If the brick breaks when you lift it from the press, you have made a mistake, but don't worry; break it up and do it again.

Because of their inherent ability to be removed immediately, it is easier to store pressed bricks. If stacked, it is best to stack them loosely to allow an airflow around them for improved and quicker drying. They can be built directly into a wall if no more than four layers are placed each time, allowing adequate drying time between levels.

9. Foundations
It is worth considering the use of strip footings alone as foundations rather than a concrete slab. It saves a lot of money in the early stages of construction and allows the use of bricks, timber, earth or even a thinner concrete paving as the floor. If you use concrete it will need to be fully carpeted or painted before you move in. Services can be laid more conveniently and leisurely and even a cellar, basement can be included before the floor is finished. Whereas a slab stops all that and everything must be ready when the floor goes down.

It is best to lay the first one or two courses with fired clay bricks with flashing (moisture barrier) below the first mudbrick, as it reduces water damage to the mudbricks and provides a skirting board inside so the mudbricks will not be damaged when you sweep and bang the wall.

Mudbricks should not be used in positions where they could be subject to excessive moisture and not in locations which require backfilling.

10. How to use the DALRAC MUDBRICK PRESS
The press should be bolted to a heavy plank of timber, steel
plate or channel section or an existing concrete slab or
foundation. Try and get as close to the soil heap as possible.

Open the press as shown in fig. 1 and load the soil loosely until it is full.
 

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