Laying mud bricks

Laying the bricks is one part of the whole business of building a mudbrick house that many owner builders find most rewarding.
It's not a job that should be left to professionals. Why should they have all the fun?
It's also a very empowering experience to discover that you can build something as solid and permanent as a brick wall.

Before you begin

As with any job, it's best to check that you have everything needed before you get going. This will avoid disruptions and result in getting the most walling up for your day's work. Here are some things to check:

Bricks: You know you have them, but where are they? They should be in stacks around the job in quantities that reflect the area of brickwork to be built. Allow spaces between stacks to park a barrow load of mortar.

Leave space too for any scaffolding needed. The aim is always to make getting the bricks from the stack to the wall without too much walking. Are the bricks dry? Damp bricks are heavier to handle and may still be shrinking. In an exposed load-bearing situation, damp bricks seem to absorb more rain water quicker than bricks that have been thoroughly dry.

Dampcourse: Ground water can be drawn up footings, base brickwork, or floor slab edges and into the walls. The action is like grease being taken from a candle and drawn up the wick to feed a flame. Do not begin laying up your walls until you know that there is a moistureproof barrier in place to prevent this from happening. Apart from chemical barriers that can be added to base work, the most common dampcourse materials used are Alcor (a bitumen coated lightweight aluminium sheet) or heavy gauge embossed P.V.C. Both of these are available in several width rolls.

Levels: Check that the base you are beginning from is level. Knowing where any high or low spots occur will enable you to compensate in mortar thickness in the first couple of courses.

Frames on Hand: It's more than likely that the wall you are about to build will incorporate a door or window. Have these on hand along with timber braces and pegs to hold them in place while you build them in.

Services: Know where to make allowances for plumbing and electrical services in or through the walls. In practice, it's rare that piping would be built into mudbrick walls. This can be incorporated within kitchen, bathroom or laundry cupboards or in the odd timber framed wall.

Electrics are another matter though. Wires and fittings are frequently built into walls and some forward planning is needed. State electricity supply authorities have rules about wires running all over the place in unpredictable directions. Prepare a plan of where you want light and power outlets and discuss with your electrician how the wires will get to any points within the walls. More details on this later.

Ties and Reinforcement: Wherever brick walls and timber posts or frames meet you will need to tie the two together using galvanized steel masonry ties. These can be purchased or made up using hoop iron strapping cut into lengths of about 250mm. Horizontal wall reinforcing material should also be on hand together with 25mm. galvanised clouts for fixing. More on ties and reinforcing later.

Tools Required: We all develop our pet ways of doing things and hence The collection of tools we use. You are likely to need-

• Tape measure - to set the height of courses and locate frames.

• Straight edge - to use as a gauge rod.

• Stringline - to lay bricks to.

• Spirit level - for setting up profiles and making sure joinery frames are set in plumb

• Small hatchet - for cutting or shaping bricks.

• Concrete mixer - mortar can be mixed by hand in a barrow but it's much more efficient in a mixer.

• Spades - for loading mixer and laying mortar on the wall.

• Trowel - Well, some people use them but hands do get muddy still and trowels become hard to hold. Hands, with or without heavy rubber gloves, are good versatile tools on their own

• Hammer - for nailing in clouts which fix ties and reinforcement.

Setting out: If the building you are laying bricks for was designed and dimensioned by a properly programmed computer you will find that all dimensions, both horizontal and vertical take account of the size of bricks and the thickness of mortar joints used. There will be almost no cutting of bricks required.

Owner built mudbrick houses can be. but~ seldom are, dimensioned with the same precision. In any case, changes do occur which throw things out and adjustments need to be made on site - Instead of making your own bricks of one size you purchased bricks of a different size. That beautiful old window you've come by just has to be incorporated despite its odd size etc. etc.. By their very nature, mudbricks are far more accommodating of change than any other type of masonry. If all else fails a whack with the hatchet will create an odd size brick to fit a space exactly. Provided you are not into accentuating joints by raking them out, the adjustment will not even be noticed. Here are some pointers to setting out the brickwork before you start mixing the mortar.

Horizontal Setout: The length of brickwork panels should always represent a number of full bricks or full bricks plus a half to a third of a brick. This is so that alternate layers or co urses can be laid in an overlapping pattern or bond. It's a good idea to loose lay some bricks on the base to see how they will fit.

Remember, if brickwork is to run over the top of door and window openings, the bond will need to continue. The space between bricks (that will become vertical mortar joints) can be adjusted as can the length of the half to a third infill brick at the end. Joints of 10 - 25mm. are common.

The longer the panel, the easier it will be to arrange the bricks. Wall panels shorter than a couple of bricks should be avoided. Short lengths of brickwork are prone to cracking and are time consuming given the amount of cutting often involved.

If unavoidable they should be seen as being supported by posts or joinery frames each end rather than providing any support themselves. Figures. 1 and 2 show aspects of horizontal set out.

Vertical Setout: It's a lot easier to cut bricks lengthwise than to split them in height. It is best therefore to plan your bricklaying job so that all vertical dimensions coincide with a whole number of courses. The most obvious height is from bottom to top of the wall. Other important heights include changes in floor level, window/door head and lintel level sill heights etc. All of this information can be calculated mathematically and noted on the building plans. To make use of it on the job what you need is a gauge rod

Making a Gauge Rod: Take a piece of straight timber. Something like a 75 x 25mm will do. Measuring from one end (bottom of wall) mark out the required overall height of the wall. Next, divide this height into a whole number of brick courses as per the following example: Height of wall (say) 2700mm. Average brick height 125mm. Allow for mortar Nominal course height 140mm. Now divide 140 into 2700 = 19.28 courses. .28 of a course is not acceptable. Divide 19 into 2700 = 142.10mm. We can now mark out 19 courses of 142.10mm each and totalling 2700mm on the rod.

Note: The greater the variation in brick height, the more mortar that will be needed to accommodate the differences hence the greater the course dimension. The gauge rod can be moved around the job and course marks transferred to posts or temporary profiles used for fixing the string line.

Profiles and Stringlines: As with any other type of brickwork, mud bricks are laid to a string line which runs between two vertical members. In the case of a post and beam frame using straight vertical posts, course marks can be transferred from the gauge rod onto the posts and the string line run between them.

Where round bush poles are used which are not particularly straight, or in the case of a loadbearing job where there are no posts, temporary uprights or profiles need to be erected.

The mortar: Theoretically, the mortar used to lay bricks should be of the same soil that went into making the bricks.

In practice, this often means that the mortar would have a higher clay content and tendency to crack then is ideal. It will also tend to stick too much to hands and tools.

Brick soil is sometimes mixed with sand to overcome these problems or a slightly different soil is selected. As with making the bricks themselves, it is important that mortar soil not contain grasses and other vegetable matter that will, in time, rot and decompose causing black mouldy marks on the walls.

Some people advocate laying mud bricks in sand and cement mortar but I fail to see the value in most cases of buying cement. Mud mortar has stood the test of time all over the world and the cement would appear an unnecessary expense in most cases.

Sieving Mortar Soil: Trying to thump a brick down to the string line only to find it is see-sawing on a rock in the mortar is a frustration easy to do without.

For this reason it's a good idea to throw the soil through a sieve before mixing the mortar. An old wire bed base is the traditional muddie's friend for this task.

Mixing: Shovel sieved soil into a rotating concrete mixer which already contains some water. (It is always easier to mix soil into water than the other way around).

Mix the soil and water until you have a creamy mixture about the consistency of the fruit cake you have seen your mother putting into the oven to bake.

Once your bricklaying experience has shown you what a workable mix is, take note of the soil/water quantities and stick to them for each mixer load.

The laying action: With dampcourse and string line in place, and an idea of the setout, it's time to start laying bricks. A small garden spade is handy for transferring mud mortar from the barrow to the wall.

Put out enough for 6 - 8 bricks at a time and run your fingers through it to spread it in a bed about 30mm. deep and about 200mm. wide (assuming the brick to be 250 wide).

Place the first brick on the mortar and up against the profile or post. As you push it down to the level of the string line the mortar will squash down to fill the entire brick thickness.

Some may ooze out and this is collected with the ball of the hand and thrown on to the end of the brick. This becomes part of the vertical joint between bricks. From then on it's a matter of repeating that process many times taking note of your original setting out and remembering to overlap or bond each successive course.

If you strike a batch of thicker bricks or are just having trouble pushing the courses down to the stringline level, try mixing a little more water with the mortar. Conversely, if the courses are consistently falling below the stringline, make up some stiffer mortar which will better support the bricks and gradually get back up to the line over a couple of courses.

One or two bricks above or below the line in a course is neither here nor there and should not worry you.

One thing to watch out for is to see that the bricks are laid flat and level across their width. Many people have a tendency to lay them with a tilt. Reinforcement: The main purpose for reinforcement in mud brick walls is to provide greater lateral stability.

Most people would be aware of all the vertical loads taken by walls in buildings. Traditionally walls have taken the weight of roof and ceiling, point loadings of beams and in some cases,upper floors. Walls which are loaded vertically are less likely to blow over.

A simple analogy would be the pile of matchboxes which can be pushed over with a little finger.

The same pile, when pressed down on with the hand, becomes quite stable. It is not a coincidence that the ancient mud brick buildings that have survived after centuries are all loadbearing and gain great stability from self weight and imposed loads.

In more recent times, Australian mud brick buildings have tended to adopt the post and beam or non load-bearing construction technique. Walls in such buildings usually require some form of reinforcement to enhance their lateral strength. The nature of reinforcing used can vary. Some masochists use a couple of strands of barbed wire spaced 75mm. apart and usually suffer ripped fingers when they forget that it's there when spreading the mortar.

Bricktor, a brand name brick work reinforcing mesh can also be used. A third alternative can be created by cutting a medium weight (say F42) fabric into single strands which leave cross pieces every 200mm.

In each case the reinforcement is stretched full length of the brick panel, turned up and firmly stapled to posts or joinery frames. Walls should be reinforced every four courses in height. See sketches.

Reinforcement details: Make sure that all courses below a layer of reinforcement have dried enough for all shrinkage to have taken place. In extreme cases you could imagine the wall to have shrunk in height as it dries leaving every fourth course hung up on the wires.

Ties: Wherever mud brick walls come into contact with built-in joinery, timber fran walls, posts etc. a galvanised metal ties should be used.

There will often be some fine cracks where wood and earth meet due simply to differing rates of expansion a contraction with changes in atmospheric moisture level. Ties do little to avoid this type of movement but do help avoid cracking due to the flexing of the building structure.
A good example of where ties are valuable would be in tieing a door frame to the mud brick wall. Generations of door banging could eventually create quite a bit of movement. I tend to go for door frame ties every second course for good measure.

Ties can be purchased or home made by cutting galvanized hoop iron straps into about 300mm. pieces and bending to shape as shown. For the avid scrounger, ties can be made up using strips cut from a variety of scrap iron. I've also used left over tray roofing clips.

Note: Ties become solidly gripped by the mud mortar and are securely fixed to the timber frame. If this connection is made before all preceding brickwork is dry you have a recipe for tearing f'rames apart as the wall dries and shrinks in height. The sketches show examples of wall ties in use.

Draft Strips: Even a small amount of shrinkage (either of timber, mud, or both) can cause a gap through which you will see daylight and through which drafts can occur.

To avoid this problem a timber or metal strip is fixed to the timber posts or frame and bricks are cut around the strip with enough space left to accommodate some mortar.

Once again, all of this can best be seen by reference to the sketches. In fixing draft strips make sure that they are very well secured by scew nails or screws.

I have seen examples where strips have parted company f'rom the post or frame. As shrinkage took place, the mud gripped the strip and a gap oecurred between it and the post.

Shrinkage, Shrinkage & Shrinkage: I've emphasised the matter of shrinkage but not without good reason.

The art of producing a good quality final product when laying and finishing mud bricks is largely the art of allowing for shrinkage that will occur.

Russell Andrews
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