Making mud bricks

The business of making mud bricks has the potential of satisfying the most devoted body punishing masochist.  It can be at least 90 per cent muscle power and 10 per cent brain power.  But it doesn't have to be like that!

If you do have masochistic tendencies don' t fret.  You will find that, even using your brain to make it easier, there is still plenty of opportunity to tire yourself out.  You may learn to make bricks almost without raising a sweat, but I don't know of any easy way out of picking them up and stacking them.
The process of making mud bricks is one involving a number of factors all of which are important.  Only after examining all of the factors will you be able to make the best choice of a brick making technique ideally suited to your circumstances.  There is no one or correct way to make mud bricks so before giving examples of brick making techniques I'll list factors you should consider.

Soil Types

OB 77 contains a detailed article on soil selection for mud bricks.
I'll not repeat myself but will give examples of how soil types will dictate the brick making technique.  Where is your soil coming from? If it is being imported to your site think carefully about where you want it tipped.

If blending soils (i.e. adding clay or sand to an otherwise deficient soil) think about how the blending is to be done.  Some techniques require soil to be stockpiled in heaps.  For others it's best to have the tip truck "run it out'' forming a long heap which is 150mm - 200mm deep by the width of the truck.
If a soil is high in clay a technique requiring mud to be sloppy enough to be poured into multiple moulds may not be a good idea.  There may be too much shrinkage and cracking.
A stiffer brew of high clay soil will be sticky and hard to get to empty out of some mixers.  A less clay rich soil which has more grit can be made wetter and will flow out of mixers and off a shovel.  It will shrink and crack less too.
In short, different soils require different mixing and moulding systems.

Site Conditions & Climate

If you are intending to make bricks on the side of a cliff during a tropical wet season, forget it.  Gentle slopes and well drained surfaces are good.  A short cut grass or sandy surface is very good.

Avoid making bricks on bare wet ground.  The bricks will weld themselves to such a surface and will be difficult to harvest when dry.  Fling a shovel or two of dry sand down first or roll out some plastic if available.
Do not make bricks on continuous plastic sheeting.  If it rains the underlay will collect water.
If making bricks in the rainy season it's hard to beat having a roof over your head.  A hay shed or the roof of your post and beam home could be used.  Walled sheds can be a problem unless good cross ventilation for drying is possible.
If you are making bricks in the open during wet weather think about how to cover them if required.
Laying out moulds in a neat line isn't being fussy.  It's making it easier to run out cover sheets quickly.  It will also make it easier later when lifting and stacking dry bricks .
Don't forget a water supply.  Carrying buckets of water up from a dam is not on.  It can take about five litres per brick made and that's a lot of buckets.  By using pumps or gravity it's a lot easier to bring water to soil than the other way around.
If rain can be a problem, hot sun can be too.  If bricks dry out too quickly they may tend to crack.  A shaded work site may also avoid brick makers cracking up.
Think about wind too.  Some brick making activities can create quite a bit of dust.  Don't choose a work site where this is a nuisance to yourself or your neighbours.
Finally, think about how you are going to get bricks from the stockpile to the wall.  Chances are you will load up a trailer or ute and drive them.  In that case, it may be more important to have a brick making area that's efficient than for it to be right at the building site.  If you are going to use a wheel barrow, a brick making area near to and preferably slightly up hill of the house would be best.

Brick Size

The size of the mud bricks you are intending to make can have a bearing on the technique you choose.  

For example, smaller bricks dry quicker and are less prone to cracking - even if the soil has a highish clay content.  These factors in turn are linked to the mixing and moulding options selected.  Smaller bricks, of course, are lighter to handle and open up the possibility of using less "macho'' labor.
In my opinion, the traditional 375 x 250 x 125mm "Victorian standard'' mud brick is too big.  Something like 350 x 250 x 90 or 100mm would be more in line with most other countries around the world.

Mixing

Probably the most important factor in making good bricks is to ensure that soils are mixed well.  Choose a mixing technique that will best allow mixing to the consistency and moulding method you require.  Mixing capacity needs to be in tune with moulding capacity.
A ready mix truck can mix a huge volume of pourable mud but if you only have moulds for three bricks you have a problem.
On the other hand, there's not much point having moulds for a thousand bricks if you only have a hoe and two gum booted feet to mix the mud.

Moulding

The type and number of moulds you require depends very much on the consistency of mud you are putting in them.

Sloppy mud has to sit in the mould for up to a day before it is firm enough for the mould to be removed.  To use the technique of pouring mud into moulds, you'll need to make a lot of moulds.
On the other hand pushing stiffer mud into a mould and removing the mould immediately will mean you get by with a single mould.

Equipment & People

There's not much sense in digging and spreading soil by hand if you have a front end loader sitting in the shed.
There's not much sense in making super big bricks that weigh half a tonne if you are the only member of the building team who has to lift them.
In other words, look at the equipment and people you have available and plan accordingly.  Remember, money is not your only asset.  Wise use of your other resources will save money and time.
If you are going to have earth moving machinery on site doing things like levelling footings or drains, see if you can make use of it in the brick making process while it's there.

Making good puddle mud bricks is basically about finding the right soil, mixing it well to produce mud, then moulding it to a brick shape before allowing it to dry in the sun.   From there on it is largely a question of scale.
I've seen people in India using nothing more than a hoe, two bare feet and a small wooden mould.  They make a few hundred small bricks each day.
I've also seen people like Chris Howe in South Australia use a 4 WD front end loader, concrete agitator and multiple moulds to make up to a few thousand bricks in a day.
There has been a tendency even for owner builders to become a bit more mechanised over recent years.  Given that most of us have to keep generating a livelihood while building, our time becomes too valuable to dig up virgin ground by hand and puddle it with hand held hoe and feet.
I'll endeavour to outline a few different brickmaking techniques suited to owner builders.  You may gain a bit from each and invent a method all of your own.  If it works for you that's all that matters.

1. Basic Manual Operation

Begin with a heap of suitable soil.
Drag soil from the side out at the bottom to make a small dam.
A long hoe is good for this.
Fill with water and pull more into it.
Work the mix into a stiff mud consistency with hoe and/or gum boots.
Preparing a brew ahead of time to let it soak overnight or over a lunch break is a good idea.  It helps ensure consistent moisture content.
Shovel mud from the dam into the brick mould(s) making sure corners are filled and trowel off with a swipe with the back of the shovel or spade.  Keeping both mould and shovel wet helps to avoid sticking.
Lift the mould immediately, dunk it in a trough of water, set it down and repeat the operation.
After a day or so the brick will be firm enough to turn on edge to expose a greater surface area for sun drying.
Once the bricks are dry to handle, stack them on edge three or four bricks high.
Lift the bottom layer off the ground by first laying down strips of timber.

2. Rotary Hoe Mixing

A one horsepower gardening type rotary hoe, or even a more powerful and wider tractor mounted one, can take a lot of labour out of mixing mud.

When we made bricks for our house 20 years ago we hoed up virgin ground into strips about 1200 wide.
If using imported soil for this method, it should be tipped out like a long garden bed on top of the ground.
If the hoeing strip gets too wide too much walking with shovels of heavy mud will be involved.
Work your way through the dry soil first to pound up any clods.
Wet the soil and continue to hoe it up into a stiff mix consistency.
Leaving to soak overnight is a good idea, before moulding.

Working from one end, make bricks each side of the mud bed.
Begin by taking mud from the edges and work inward.
If you have to walk around in the mud looking for a bit that's just right for moulding your soil is not mixed well enough.
You'll soon learn how far out to make the first brick to avoid either walking too far or having mud left over as you work your way along.
If blessed with plenty of helpers, don't work on top of one another.  Begin each person at a different point along the mud bed.
Where a tractor is available but not a rotary hoe, driving up and down can mix the mud.
A blade would be handy to keep the mud in a tidy row.

3. Puddling Hole Method

When soil is collected in a depression in the ground or in a steel car trailer it can be converted into mud largely by the action of soaking with water.  I often refer to this as allowing the brew to "marinate''.
In the case of a hole in the ground, the action can be speeded up by driving a small tractor around in it or by use of a rotary hoe.  If the hole is too deep however, the rotary hoe may become bogged or at least too heavy to handle.
One Melbourne brick maker used a small front end loader to puddle then to drop a bucket of mud on a sheet of flat tin from where it was shovelled into individual moulds.  The tin enabled the shovel to slide under the mud without picking up dry virgin soil.
The metal in the bottom of a trailer acts in the same way.  Mixing in this case will probably be mainly by soaking (time) and some stomping or use of gardening implements.
One would need to question the work involved in loading the soil into the trailer in the first place.
At least the trailer can be towed to various work areas and with the tailgate down, shovelling would be from about knee level down with little lifting of wet mud.

Russell Andrews