Basic Masonry Techniques

By: J. van Winden

CONTENTS

TECHNICAL TERMS

BONDING OF WALLS

General effect of bond / Half-block bond / Other types of bond

HANDLING THE TROWEL

Preparing the bed joint / Removing surplus mortar

THE FIRST WALL

Setting out / Organizing the work / Preventive measures / The first blocks / The first course / The second course / Toothed end / Stopped end / Marking and cutting blocks

QUOINS

Second course / Walling between quoins / Fixing the mason line / U3e of the tingle plate / Completing the course

BONDING PROBLEMS

CORNER BONDS

Corner bond for footings / Corner bond for a rising sandcrete wall / Corner bond for rising landcrete wall

T-JUNCTION BONDS

T-junction bond for footings / T-junction bond for rising sandcrete walls / T-junction bond for rising landcrete walls

CROSS JUNCTION BONDS

Cross junction bond for footings / Cross junction bond for rising sandcrete walls / Cross junction bond for rising landcrete walls / Footings - Plinth course - Rising landcrete wall

PIERS

Attached piers / Simple piers / Footings for piers / Bonds for sandcrete piers / Bonds for landcrete piers

TECHNICAL TERMS.

Before describing the methods used in bonding it is necessary to briefly define and exnlaln a few of the technical terms commonly used.

SUN-DRIED TRAINING BLOCKS: These blocks, as the name implies, are dried in the sun, because they do not contain cement (Fig. 1). They are often used by beginners during their first terms of in-centre training, as they are easy to make and to handle.

The dimensions of these blocks are approximately 29 cm x 14 cm x 11 cm, which allows us to construct complicated bonds with them. They can be used to make an excellent inside wall also, as the following chapters will describe.

LANDCRETE BLOCKS: These are blocks used for actual building (Fig. 2).

SANDCRETE TRAINING BLOCKS: These are specially made small sandcrete blocks with the approximate dimensions of 24 cm x 14 cm x 11,5 cm; so they can be used to teach the making of more complicated bonds (Fig. 3).

Like the sun-dried blocks, they are often used in training because they are easy to handle. As they are made with cement they can be used for a long time before they wear out.

SANDCRETE BLOCKS: This type of block is used for actual building (Fig. 4).

-3/4 - 1/2 - 1/4 - BLOCKS: These are parts of blocks obtained by cutting a block through either the centre line or the quarter line, less half the thickness of the joint {Fig. 5). The cut is made along the width, not along the length. A special block gauge may be used for marking off the different sizes.

HEADER: A block is known as a header when it is placed in a wall so that its smallest face is exposed (Fig. 1, below).

BED: The under-surface of a block, or the mortar on which the block is laid.

STRETCHER: If the biggest face of a block is exposed, the block is called a stretcher (Fig. 1, next page). This is the way most blocks are laid in Rural Building, and we say that the block is laid edgewise. If a block is laid flatwise, so ft is actually showing the top face, it is also called a stretcher (Fig. 1, below).

COURSE: This is the term applied to each layer or row of blocks, with the bed joint included (Fig. 1, below).

BED JOINT: This is the horizontal mortar joint between two courses (Fig. 1).

CROSS JOINT: The vertical joints between the blocks (Fig. 1).

QUOIN: The quoin is the outside corner of a wall or the external angle on the face side of the wall (Fig. 1).

ANGLE BLOCK: This is the block which actually forms the corner in each course (Fig. 1).

STOPPED END: A plain vertical surface which forms the end of a wall (see -------).

TOOTHED END OR TOOTHING: The form produced at the end of a wall by recessing every other course by half a block (Fig. 1) in order that the wall may be extended later using the same bond.

RACKING BACK: As an alternative to toothing, the end of a wall may be set back half a block at each course (Fig. 1). This is also done so that the wall may be extended later using the same bond.

BUILDING UNIT: This refers to the dimensions of a full block, plus one joint. For sandcrete blocks the building unit is 25 cm high by 48 cm long (2 cm joints).

FOUNDATION: The base, usually concrete, on which the building rests. It is usually set below ground level, and is the only part of the building in direct contact with the ground.

FOOTINGS: The courses laid directly on top of the foundations; usually three flatwise courses of sandcrete blocks (see page 35).

PLINTH COURSE: The edgewise course of sandcrete blocks laid on top of the footings (see page 35).

RISING WALL: The edgewise courses of sandcrete or landcrete blocks which build up the rest of the wall (see page 35).

BONDING OF WALLS

The practise of blocklaying requires a complete understanding of the correct arrangement of the blocks forming a wall. This correct arrangement of blocks, regardless of the method, is known as bonding.

The blocks are placed so that they overlap each other and care must be taken to ensure that as far as possible no vertical joint is immediately above another vertical joint in the course below.

GENERAL EFFECT OF BOND

Fig. 1 shows a wooden pole placed vertically on soft ground. If this pole has to carry a heavy load it will sink down into the soil, because the total area on which the pole rests on the ground is far too small to support it (Fig. 2).

A possible solution to the problem is shown in Fig. 3: a board is laid flat on the ground and It new carries the pole with the load. in this way the total load is distributed over a larger area of ground and it is Impossible for the pole to sink down.

If a wall is built up by simply placing blocks directly above each other, we say the wall is built without bond. If a heavy load is put on top of this wall (Fig. 4) the column of blocks immediately under the load tends to give way and sink down.

In order to make the wall stronger in itself and able to distribute loads properly, the builder applies the so-called half-block bond.

A properly bonded wall which receives a heavy load will distribute the pressure over a large number of blocks and therefore over a much greater area (Fig. 5).

HALF-BLOCK BOND

The simplest form of bonding is that where all the blocks are laid down as stretchers, each block overlapping the one below by half its length (Fig. 1).

This form of bonding is only suitable where a one-block thickness of the wall is sufficient. in Rural Building the most common wall thickness is 14 cm when land-crete blocks are used and 15 cm when using sandcrete blocks; provided that they are laid edgewise.

If for some reason a thicker wall is required, the blocks may be laid flatwise. By doing this the wall thickness will be increased to 23 cm, 29 cm or even 46 cm depending on the type of block and the way the blocks are laid.

OTHER TYPES OF BOND

There are many types of bond in use, the two most common being the English Bond (Fig. 2) and the Flemish Bond (Fig. 3), both of which are used with bricks.

Bricks are smaller blocks with approximate dimensions of 24 cm x 11,5 cm x 7 cm.

ENGLISH BOND: This bond consists of alternate courses of headers and stretchers. The centre of any stretcher is in line with the centre of the header in the courses above and below.

FLEMISH BOND: This bond consists of alternate headers and stretchers in the same course. Again, the centre of any stretcher is in line with the centre of the header in the courses above and below.

HANDLING THE TROWEL

In the process of laying blocks, the brick trowel is used to perform a series of operations during which the trowel is seldom put down or changed from one hand to the other.

All operations require free and easy manipulation of the trowel from the wrist and it is therefore essential to master the correct handling of the trowel.

Fig. 1 illustrates ihe correct grip on the handle, with the thumb resting on the ferrule. The thumb must be in this position in order to manipulate the trowel skillfully.

The amount of mortar picked up from the headpan will depend on the nature of the job, but for the trainee it is advisable to pick up a sufficient amount to lay one training block, i.e. a heaped trowel. Later, when working with the common big blocks, it will become necessary to pick up two troweliuls of mortar.

PREPARING THE BED JOINT

Place the mortar in the middle of the wall or the marked position of the first course and spread it out by a pushing movement with the back of your trowel, into a layer about 3 cm thick (Fig. 2).

Next draw the point of your trowel through the centre of the layer, making a mortar bed suitable for the block (Fig. 3).

A block laid on a bed prepared in this way will at first rest on the two outer edges, but when it is pressed down to its correct position it will not only squeeze mortar from the front and back of the block but will also squeeze it into the valley in the centre. in this way a solid bed is formed (Figs. 3, 4, & 5).

- NOTE: All the tools mentioned in this section on masonry techniques are described in the Rural Building Reference Book, pages 3 to 15.

NOTES:

REMOVING SURPLUS MORTAR

Before and after the block is layed, a certain amount of mortar will project from both sides of the wall. This must be removed before it drops down, as one of the most important principles of the Rural Builder is to work as economically as possible. This means saving materials. Fig. 1 shows the position of the trowel for these operations.

The surplus mortar recovered on the trowel is usually taken to form the cross joint between the last laid block and the previous one, or it is returned to the headpan.

THE FIRST WALL

SETTING OUT

Before actual building operations are started, you must know the correct position and dimensions of all the parts of the building.

This information is given in the plan or drawing of the building, which of course must have been already prepared and at hand.

The positions of the walls, for instance, have to be marked on the ground according to the measurements given on the plan before any building operation starts.

This operation is called 'setting out" and we will deal with it repeatedly here, because it is one of the most Important preparatory steps in building.

ORGANIZING THE WORK

The workplace has to be well organized in order to operate smoothly and safely.

Building materials such as blocks and mortar should be neither too close nor too far away from the wall being erected. A working space of about 90 cm will usually be all right. The blocks should be neatly stacked, not just thrown in a heap; and there should always be an adequate supply available, so that work is not delayed by waits for materials.

Keep your tools together and near your workplace so they are within easy reach. When you use a tool, put it back Immediately afterwards so that it cannot fall off the wall etc. and injure you or other workers. Make a habit of putting your tools down in a way that prevents accidents.

- NOTE: You cannot expect to produce a good job with your tools and materials always scattered around. Neathess and orderliness show the professional.

Never throw, kick or drop tools as you might damage them.

Work on one side of the wall only. As the wall becomes higher, you won't be able to move from side to side anyway.

PREVENTIVE MEASURES

Almost all of the building in the Northern and Upper Regions of Ghana is done during the dry season, with its high temperatures and low humidity. These conditions are Important and our building procedures must take them into consideration to prevent problems with drying out.

Before you put the mortar down and spread!:, thoroughly wet the top of the foundation or the already laid course.

Do the same thing with the block that you are going to lay next. This is to prevent the block from absorbing too much moisture from the mortar. The porous landcrete or sandcrete blocks quickly suck in any moisture they come into contact with. This process is known as absorption. If the blocks absorb too much moisture from the mortar, it will not be able to set properly, and the joints will be weak. By sprinkling sufficient water onto the blocks, we ensure that there will be enough moisture left in the mortar to allow it to harden properly.

It is also important to never spread too much mortar at one time. Some masons prepare the mortar bed in advance for five , six or even more blocks in order to speed up the work. This is wrong.

While the first blocks are placed, lined-out, and levelled, the rest of the mortar is exposed for too long to the sun and air.

Due to the high temperatures and the low humidity, the mortar dries out very fast. As a result the mortar becomes too stiff, making it difficult to lay the last blocks and weakening the grip between the mortar and the block. The end result is a weak wall.

The builder should always keep in mind the climate and never spread more mortar than is actually needed.

THE FIRST BLOCKS

After you have wetted the block and the area where it is supposed to be set, spread the mortar according to the method described on page 12. Set the block immediately onto the mortar bed and press it down firmly and evenly (Fig. 1).

If the bed has been spread correctly, only a few taps with the handle of the trowel will be needed to adjust the height of the block. The height is checked by couii ar-ing the height of the block with the gauge marks on the straight edge (Fig, 2).

Next, plumb the block with the spirit level along the stretcher face and the header face as shown in Fig. 3, The pressure on the block will have squeezed out some of the mortar. Trim off this excess, collect it on the trowel end return it to the headpan.

If you don't use enough water to make the bed, the block will not come up to the required height; it will sit too low. If on the other haad too much mortar is used, the block will sit too high.

Do not try to correct problems like this by pushing some mortar from the edges towards the inside of the bed using your fingers; or by knocking hard on the top of the block to try and force it down. These are very poor practices. instead, simply remove the block and re-spread the mortar.

At the beginning of the training you will have to re-lay blocks quite often. As you gradually gain experience you will be able to spread just enough mortar to lay one block, without any of the problems mentioned above.

Lay the secciid block at a distance of four building units and one joint away from the first block (Fig. 4). Hold the straight edge against the stretcher faces of the twu blocks to make sure that they are in line.

REMEMBER: RETURN SURPLUS MORTAR TO THE HEADPAN

THE FIRST COURSE

Because the first two blocks are in line and at the same height, we can complete the course without using the spirit level, only using the straight edge. Starting from either block (but still working on only one side of the wall) more blocks are inserted between the first two (Fig. 1).

Their height is adjusted by placing the straight edge on top and pressing the blocks down until the top surfaces of all the blocks touch the straight edge equally, along their whole length.

Line out the course (make it perfectly straight) by holding the straight edge against the stretcher faces and moving the blocks until they touch it along their Ml length.

During these operations take care to maintain the proper distances between the blocks. The next step is to fill the remaining open gaps between the blocks with mortar, thus forming the cross joints. This job is done by closing the back of the gap with the aid of a small wood float while carefully pushing the mortar down into the joint with the trowel (Fig. 2).

All cross joints must be completely filled up with mortar so that no holes are left, which would reduce the strength of tht course and the whole wall.

All the excess mortar which has dropped down or was squeezed out of the bed must now be collected and returned to the headpan to be mixed with the rest of the mortar.

THE SECOND COURSE

Lay the first block of the second course with its centre exactly above the first cross joint so that it overlaps both blocks below equally.

No matter what sort of wall-ending is desired, the first block of the second course is always a full block laid above the first cross joint between two stretchers. This is known as the 1-2-1 rule. By doing this you maintain the half-block bond throughout the wall (Fig. 1)

After you check the height of this block, you must plumb its face. Hold the spirit level vertically along the face of the lower block with one hand, while with the other hand you move the upper block until its face is also in full contact with the spirit level, and the bubble is in the centre of the tube.

Follow the same operation with the second block, laying it above the last cross joint in the lower course. insert the remaining blocks between them according to the method used for the first course.

The construction of any subsequent course is merely a repetition of the above operations and will result in a wall with racking back at both ends (Fig. 2).

- NOTE; If the builder has a choice between racking back and toothing, racking back should be the preferred method. This is because the joints used in toothing are difficult to fill properly when completing the wall, which often results in a weak grip all along the joints.

TOOTHED END

The construction of a wall with a toothed end starts with the same operations used for a wall with a racking back. After you lay the first block of the third course, the next block you lay forms the toothed end. As this block projects past the one below by more than half its own length, it should normally tip over on its projecting end.

To prevent this, a temporary support must be provided until the block is overlapped by the first block of the fourth course and the mortar has set hard. This temporary support is preferably a short piece of board cut to the height of the block plus two bed joints. The upper and lower ends of the supporting board may be chamfered slightly to keep it from wedging between the blocks when it is removed (Fig. 1).

This block must be exactly above the first block of the first course. To ensure this, hold the spirit level against both header faces and make any necessary corrections. It is not necessary to level the top face if the stretcher and header faces have been plumbed.

The construction of further courses is again only a repetition of these operations.

STOPPED END

The construction of a wall with a stopped end is very similar to that with a toothed end. The sequence of operations is exactly the same except that instead of the supporting board, half a block is added at the end of the second course before the third course is laid (Fig. 2).

This means that there are no gaps left as in the toothed end, so it is called a stopped end,

MARKING AND CUTTING BLOCKS

It is usually not possible to construct walls using only full blocks. in most cases 1/4, 1/2, and 3/4 blocks or intermediate sizes are also required. The previous description of the stopped end, for example, has shown the need for 1/2 blocks.

This does not mean that 1/2 blocks are obtained by simply cutting a full block into two identical halves. This is because the cross joint and its thickness must be considered.

Therefore, the 1/4, 1/2, and 3/4 blocks are actually that part of a full block minus half the thickness of the cross joint (Fig. 1).

Before cutting a block, mark the required size around all the faces. To prevent mistakes and to speed up the work, use a block gauge (see Rural Building Reference Book, Tools, page 12). Position the appropriate setting of the gauge against the block, then mark off the measurements on the block face using a pencil or a nail.

Set the marked block on a small heap of sand and then cut it with the block scutch by repeatedly and carefully knocking along the mark, making a groove in the surface. Direct the blows close to each other all around the four faces and continue unfil the block breaks apart along the groove (Fig. 2).

Trim the resultant rough header faces, if necessary, with the edge of your trowel blade (for landcrete blocks). When cutting sandcrete blocks, you should use the block scutch for trimming (Fig. 3).

- NOTE: Avoid cutting blocks on hard ground: they can easily break into Irregular pieces and be wasted.

Never cut blocks on a scaffold for the same reason, also because they might fall and injure someone below.

It is always better to prepare in advance the number of blocks that you think will be needed that day.

Do not use blocks which are cracked; these must be replaced by good blocks or the wall will be weakened.

QUOINS

When external walls are constructed the corners or quoins are built first, to a height of several courses. Usually it is best to build six courses as this will reach to about 1,5 m high, the so-called scaffold height; and in most cases this will be half of the total height of the wall. The walling between the courses is completed later, course by course. The accuracy of the whole wall is determined by the corners, so great care must be taken to build them properly.

At the beginning of training, the positions of the quoins are determi'ied by marking them out on the floor using the mason square.

A quoin is constructed in the following manner:

Blocks are sometimes not correctly shaped, so the first block or angle block must be chosen carefully so that all its faces are square to each other.

As you lay the angle block, stand close to the foundation with your head vertically over the block. You should be able to see that both outer faces of the block are aligned with the mark below (Fig. 1). After this the block has to be accurately levelled and plumbed.

Use the straight edge with gauge marks to ensure that the block is laid at the correct height. Hold the straight edge vertically against the block; the top edge of the block should correspond to the gauge mark (Fig. 2).

Now you have to make certain that the header face and the stretcher face are truly vertical. To do this hold the spirit level against one face about 5 cm from the corner, keeping it in this position while with your other hand you move the block until the bubble in the tube is centered. This operation must be repeated with the other face of the block (Figs. 3 & 4).

Now lay several blocks in each direction according to the method described before. On the quoin stretcher side three more blocks should be laid; followed by four on the header side of the quoin. This will be a sufficient base for building up a height of six courses with either a toothed end or racking back (Fig. 1 below).

Use the mason square to make sure that the quoin has an angle of 90 degrees. Hold it against the quoin so that both of the blades fully touch the faces of the blocks. Repeat this operation after turning the square around, so that the direction of the blades is reversed.

SECOND COURSE

Following the 1-2-1 rule, the first block of the second course will not be the angle block; but the one covering the cross joint between the quoin stretcher and the adjoining stretcher. If the angle block were laid first it could get pushed out of position when the other blocks are laid. The correct method fixes the angle block in position by the cross joint between it and the first block. A further reason for this procedure is that the cross joint between the quoin headers and the adjoining stretchers has a different thickness than the other cross joints. This problem will be explained later when we come to bonding problems.

To complete the second course use the same method as described for the construction of the first course.

- NOTE: The arrangement in any course is repeated in the courses two above or two below it. Therefore only two alternating block arrangements are used.

WALLING BETWEEN QUOINS

When both corners of a wall have been built up to a height of six courses, it is necessary to fill in the blockwork between them. This is done with the aid of the mason line and either nails, pins, or line bobbins.

FIXING THE MASON LINE

If nails or pins are used, insert one of them in the bed joint at one corner so that the line will be level with the upper edge of the course. Fix the mason line to the nail or pin without using a knot, as shown in Fig. 2. This is so that later it can be easily removed.

Stretch the line taut to prevent any sagging, and push the second nail or pin into the corresponding bed joint in the opposite quoin. The line should now be level with the top of the course to be built; and about 2 mm or the thickness of a trowel blade away from the blockwork. Put a wedge of paper between the wall and the line to keep the distance of 2 mm. The line should be horizontal.

If you use line bobbins instead of pins, take one with the line fastened around the screws and engaged in the saw cut; and position it with the notch against the corner of the quoin so that the line is level with the top edge of the course to be built. At the opposite quoin insert the line in the saw-cut of the second bobbin and set it at the correct height against the corner. Stretch the line taut and secure it by winding around the screws (Fig. 1 below).

The tight mason line holds the bobbins against the corners, keeping them in position. Once the line has been fixed in this manner no further adjustment is needed, unless the line starts to sag and needs tightening.

After one course is completed, simply slide the bobbins up the corners to the level of the next course.

USE OF THE TINGLE PLATE

If the line is stretched over a longer distance, it will tend to sag and will no longer provide a straight guide. in the case of a long wall where the distance between the bobbins exceeds 6 m, it becomes necessary to use one or more tingle plates (Fig. 2 below). This is done to keep the line from sagging.

The tingle plate must be set on a so-called tingle block. Lay this block plumb, in position and at the correct height in the course to be built. This block keeps the tingle plate at the required height to support the mason line. Place the plate flat on the block, and weight it down with a half-block. Tne taut line is passed under the outer nibs and over the centre nib (Fig. 2).

COMPLETING THE COURSE

Now lay the blocks to complete the course. Take care that the outer top face edge of each block is level with the line.

At the same time be sure to keep the lower stretcher face edge in line with the edge of the course below. Avoid the tendency to lay the blocks coo close to the line; the 2 mm distance must be maintained and checked from time to time by sliding the trowel blade between the line and block.

If the blocks are laid correctly, plumbing and levelling are not necessary. It is advisable however to check the face of the wall for a possible overhang, using the straight edge.

BONDING PROBLEMS & CORNER BONDS.

After you have filled the cross joints, carefully rake out all the joints of the freshly laid courses to provide an additional grip for the plaster.

BONDING PROBLEMS

Problems arise when we use different types of blocks in the same wall. Usually in Rural Building we use sandcrete blocks for the lower courses of a wall to avoid problems with dampness, and landcrete blocks for the higher courses. Unfortunately the dimensions of sandcrete blocks and landcrete blocks do not match up well to each other. This means that it is not as easy to maintain a half-block bond as it is in a wall made up of only one kind of block.

For example, a sandcrete block has dimensions of 46 x 23 x 15 cm. A sandcrete half-block has the dimensions 22 x 23 x 15 cm. Even when the sandcrete blocks are cut in half they still will not match up exactly to the landcrete blocks (see the table below).

	Full block	Half block
Sandcrete	46 x 23 x 15	22 x 23 x 15
Landcrete	29 x 22 x 14	13, 5 x 22 x 14

The dimensions of the 1/4 and 1/3 blocks also do not correspond, so in order to maintain the half-block bond between the sandcrete and landcrete courses we would have to make quite an adjustment.

Practically this means that although it would be better, we cannot maintain exactly a half-block bond between the sandcrete and landcrete. They must be considered as separate parts of the wall, properly bonded In themselves but not necessarily showing a half-block bond between them.

CORNER BONDS

CORNER BOND FOR FOOTINGS

The materials used for footings are sandcrete blocks which must be laid flatwise, giving a wall thickness of 23 cm. Since this measurement exceeds the length of a half-block by 1 cm, the first cross joints following the quoin stretchers must be 3 cm wide instead of the normal 2 cm. All the other joints are still 2 cm thick. By doing this the half-block bond is maintained (Fig. 1 below).

There are of course two other ways to maintain the half-block bond:

All the cross joints directly following the quoin header could be reduced to a thickness of only 1 cm. The effect would be the same but these joints would be difficult to fill properly, which could result in a weak quoin.

All stretchers following the quoin headers could be cut to a length of 45 cm. This takes time and may damage the blocks.

In general, it is best not to use these last two methods.

CORNER BOND FOR A RISING SANDCRETE WALL

So-called wet rooms such as kitchens, showers and toilets must be built with sandcrete blocks. This is to avoid any damage to the walls caused by moisture.

If landcrete blocks are exposed to moisture for a long time the blocks will start to expand. This pushes the plaster off the walls and makes them weaker and weaker until finally they collapse under their own weight.

Rising walls in Rural Building are generally built by laying the blocks edgewise. When sandcrete blocks are used the wall has a thickness of 15 cm.

In order to avoid making too many cross joints within the quoin area, each quoin header as well as each quoin stretcher is followed by a full block.

To maintain the required half-block bond, a 7 cm lack of overlap has to be made up. This is done by inserting a 5 cm block between the first two stretchers that follow the quoin headers (5 cm plus 2 cm joint equals 7 cm). Almost every building project uses thin blocks for **pings or rain gutters etc., and these specially made blocks can be simply cut in half and used to fill the gaps (Fig. 1 below).

CORNER BOND FOR RISING LANDCRETE WALL

As far as bonding is concerned, the footings, the plinth course and the rising land-crete wall are all regarded separately. They are properly bonded in themselves but don't necessarily show a half-block bond, especially between the plinth course and the landcrete wall.

As Fig. 1 illustrates, a half-block bond between footings and plinth course (both sandcrete) is possible despite the 4 cm setting back (c) and should be maintained.

PLINTH COURSE:

Since the rising wall is erected exactly in the middle of the footings, the plinth course has to be cet back 4 cm from both faces: 23 cm (thickness of footings) minus 15 em (thickness of plinth course) divided by 2 equals 4 cm (at both sides).

The angle block (A) has to be shortened by 3 cm because of the setting back, thus we automatically make the correct half-block bond on the quoin stretcher side. The first two cross joints (a & b) following the quoin header must be widened to 4 cm each to overcome a lack of 4 cm in overlap. By doing this we distribute the lack of 4 cm over two joints equally.

RISING LANDCRETE WALL:

As already stated, the rising landcrete wall is regarded separately from the plinth course. This is because the dimensions of the landcrete and sandcrete blocks prevent the construction of a half-block bond between them.

However, one important rule must be observed: No matter what part of the construction or what material it consists of, each quoin header must be overlapped by a quoin stretcher; each quoin stretcher is automatically followed by a quoin header (Fig. 1).

To maintain the half bock head within the landcrete wall, all the cross joints directly following the quoin stretchers must be widened to 3 cm. All other joints remain the same.

T-JUNCTION BONDS

The term T-junction is given to connections between walls which form a T shape, although it is not essential that the angles be right angles. This situation occurs most often where outside walls are met by inside walls.

T-JUNCTION BOND FOR FOOTINGS

Like quoins, the T-junctions are built first or at the same time as the quoins, and the walling between them is completed later.

The first block to be laid is the first block (A) of the inside wall: it will be seen as a header in the face of the outside wall (Figs. 1 & 2). This followed by a 1/4 block (B) at one side of it in the direction of the outside wall, and by a full block (C) on the other side (Fig. 2). This is followed by laying full blocks in all three directions.

The second course, and all the alternate courses, go through in the direction of the outside wall, that is, they do not share a block with the inside wall. Thus the inside wall is bonded to the outside wall only at alternating courses: at the 1st, 3rd, 5th etc. courses (Figs. 1 &2).

The second courj e starts with a 3/4 block overlapping the header below by 10 cm but from the side opposite from the 1/4 block below. This is followed by full blocks in all three directions (Figs. 1 & 2).

The cross joints between the headers of the inside wall (a) are 3 cm thick and must be exactly in line with the centre of the headers (Fig. 1). The cross joints directly following the blocks which are bonded to the outside wall are also 3 cm thick (Fig. 2). All the other joints are 2 cm thick.

- NOTE: All courses with odd numbers (1st, 3rd, 5th etc.) share one block with the inside wall; these blocks are seen as headers in the face of the outside wall, each one next to a 1/4 block

All courses with an even number (2nd, 4th, 6th, etc.) go through in the direction of the outside wall and contain a 3/4 block at the opposite side of the 1/4 block below and above.

The illustrations below show three other possible constructions for T-junctions in footings, all of which maintain the half-block bond (Figs. 1, 2, & 3)

Which method is used depends on factors such as the distance between the junction and the next quoin, or the next junction.

One way to find out the best choice is to lay out the first course of blocks without mortar, and try different arrangements. in tills way the builder can decide what will be the best final arrangement.

If two or more constructions are possible the Rural Builder should chose the most efficient method. This is the method that wastes the least time and materials.

Specifically, the more blocks that have to be cut the more time will be needed; and if for example only 3/4 blocks are needed, the remaining 1/4 blocks are wasted unless there is a need for them somewhere else.

By comparing the four possible constructions (Figs. 1 & 2 on page 37, and Figs. 1, 2 & 3 at left) we see that the first three can be carried out without any waste of blocks while in the last case (Fig. 3) all the 1/4 blocks are left-over.

As far as efficient work is concerned, we see that for the first method (page 37) only one cut needs to be made for two courses as both parts of the block are used. The alternatives shown in Figs. 1, 2 and 3 need two cuts for two courses.

By considering carefully the advantages and disadvantages of the four, we see that the first construction is the best, the 2nd and 3rd constructions are less good and the 4th construction is the worst. Therefore the first type should be used whenever possible.

T - JUNCTION BOND FOR RISING SANDCRETE WALLS

Since the footings are normally 3 courses high, the third course of the footings contains the block which bonds the inside wall. Thus the first course of the rising sandcrete wall must go through in the direction of the outside wall to cover the header of the footings (see previous pages).

The first block of the rising wall is placed so that it extends past the header below by 12 cm on one side (Fig. 2, block A). Don't forget to set this block back from the face of the footings by 4 cm. This block is followed by full blocks on either side (Fig. 2, blocks B). The inside wall starts with a 1/4 block (Fig. 1, block C), this too is followed by full blocks.

The second course of the T-junction begins with the full block of the inside wall that is bonded into the outside wall (Figs. 1 & 2, block D). This is followed by a 3/4 block (Fig. 2, block E) on the same side of the header where the stretcher (block A) below projects by 12 cm. Continue with full blocks in all three directions.

The odd-numbered courses of the outside wall contain widened cross joints to catch up with the half-block bond. The first two cross joints opposite the 12 cm project-ton (Fig. 2, a & b) are 4 cm thick , followed by one more joint which is 3 cm thick (not shown). in this way the half-block bond is maintained.

The same must be done with the first three cross joints following the bonded block of the inside wall (Fig. 1).

T-JUNCTION BOND FOR RISING LANDCRETE WALLS

PLINTH COURSE: Except that the blocks are laid edgewise rather than flat, the plinth course is simply a repetition of the footing course two courses below (Fig. 1, blocks A & B).

The only difference is that the first two cross joints in the inside wall are widened to 4 cm each, in order to maintain the half-block bond in relation to the footings.

Do not forget to set the plinth course back from the face of the footings by 4 cm,

RISING LANDCRETE WALL:

Since the landcrete wall is 1 cm thinner than the plinth course, It is essential to continue the "good" face of the plinth by setting the landcrete blocks flush with the outside face of the plinth. The Rural Builder should choose one face of the inside wall to be the "good" face; where the surface of the plinth course is flush to that of the rising wall. This is the face from which the plumbing and levelling are done; the Rural Builder should alway work from this face. On outside walls the "good" face is normally the outside face.

The first block of the landcrete wall is the one which is shared by the inside and outside walls and covers two cross joints (Fig. 1, block C). It is followed in all three directions by full blocks.

The second course of the rising landcrete wall begins with a full block centred exactly over the header below, with 1/4 blocks on either side (block D). All of the other courses in the rising wall are repetitions of these two courses.

CROSS JUNCTION BONDS

A cross junction, also called an intersection, consists of two continuous walls which intersect, or cross each other.

The following are only a few examples out of many methods for bonding at a cross junction. in actual practice the dimensions of the building will not always permit the use of these particular bonds. in such cases some adjustments must be made.

The essential requirements for a cross junction always remain the same:

avoid making continuous cross joints; and

try to use a minimum number of cut blocks.

CROSS JUNCTION BOND FOR FOOTINGS

The first course consists entirely of full blocks (Fig. 1). The through-going block (A) projects equally from both sides of the crossing wall. This block has cross joints of 2,5 cm on each end, but all the other joints are still 2 cm thick (Fig. 1).

The second course starts with a full block centred over the through-going block below. This block is followed by 1/4 blocks on either end. The 1/4 blocks each have one cross joint which is 2,5 cm think. All other joints are still 2 cm thick.

The second course of the crossing wall continues with 3/4 blocks on both sides. This is followed by full blocks in all four directions.

The second possible construction is where the crossing walls enclose a cross joint (Fig. 1, a). in this case two 3/4 blocks are used in the first course while the remaining 1/4 blocks are kept aside for the second course (Fig. 1).

The two 3/4 blocks of the first course are arranged so that they are at right angles to each other. One of the 3/4 blocks always starts from the middle of the crossing wall while the other is placed on either the right or left side of it. This is followed in all four directions by full blocks (Fig. 1 below).

The second course begins with a full block crossing the through-going wall below and overlapping equally at both sides. This block covers three cross joints at once instead of two as in the last method. The first block is followed by the 1/4 blocks placed on opposite sides from the 3/4 blocks below. The second course is continued with full blocks in all four directions (Fig. 2).

Each 1/4 block must have one cross joint of 2, 5 cm; all other joints remain the same, 2 cm thick.

Try to figure out more possible ways to do a cross junction bond, and discuss the results with your fellow trainees, your instructors, and your foreman on the building site.

CROSS JUNCTION BOND FOR RISING SANDCRETE WALLS

The smaller wall thickness in relation to the block length makes it necessary that all cross junction bonds for rising sandcrete walls contain a block that is 5 cm thick (compare with corner bonds for rising sandcrete walls, above).

The opposite illustrations show the most economical method for constructing a cross junction. Apart from the one 1/2 block and one 5 cm block, both the first and second courses contain only full blocks.

Fig. 1 shows the first course. The through wall consists of only full blocks, while the crossed wall starts on one side with a 1/2 block combined with a 5 cm block. This is continued in all four directions with full blocks. The through-going block (A) must extend past the crossed wall by 24 cm, which is the length of a 1/2 block plus the joint.

In the second course, the wall which was crossed in the course below now goes through. The through block (B) again extends past the crossed wall by 24 cm, but on the side opposite from the 1/2 block in the course below. Block B is followed on its left-hand side by a 1/2 block (C) combined with a 5 cm block. This is continued in all four directions with full blocks (Fig. 2).

In the first course the crossing block and the 1/2 block form a corner. This is also true in the second course but the corner is diagonally opposite from the one in the first course below.

- REMEMBER: All through courses in either wall consist of full blocks only. Ail crossed courses in either wall contain one 1/2 block combined with a 5 cm block.

The second method of making a cross junction in a sandcrete wall is different from the first method because 3/4 and 1/4 blocks are used instead of 1/2 blocks.

Because of this the rules for this bonding method are also different:

All through blocks (Figs. 1 & 2, blocks A & B) project from the crossed wall by 12 cm at one end (12 cm is 1/4 block plus the joint). These blocks are followed by 1/4 blocks at the other end (Figs. 1 & 2).

All crossed walls contain a 3/4 block (Figs. 1 & 2, blocks C & D) set directly against the through-going block. This 3/4 block is on the opposite side from the 1/4 blocks in the course below (Fig. 1). The crossed wall continues with a full block (Figs. 1 & 2, blocks E & F) and a 5 cm block, on the other side from the 3/4 block.

NOTE: The above method involves a lot of block-cutting, which makes it less efficient than the other method.

Try to figure out more possibilities and discuss them with your fellow trainees, your instructors and your foreman on the building site.

CROSS JUNCTION BOND FOR RISING LANDCRETE WALLS

The arrangement of blocks to construct a cross junction with landcrete blocks is almost the same as for the footings (see previous pages).

Fig. 1 shows the bond for all courses with an odd number (1st, 3rd, 5th, etc.). These consist of full blocks only. The through block (A) is set exactly in the middle of the crossed wall.

The arrangement for courses with an even number (2nd, 4th, 6th, etc.) is shown in Fig. 2. These courses also start with a full block (B) set exactly across the middle of the through-going block below. This block is followed by 1/4 blocks on Its ends and 3/4 blocks on its stretcher sides. This is continued in all four directions with full blocks.

Another method of bonding uses the cut blocks in alternate courses, unlike the last method which used all cut blocks in the same course. There is no waste in either method.

The first crossing (Fig. 1) is formed by two 3/4 blocks which project equally from the crossed wall, meaning that the joint between them is exactly in the centre of the crossed wall. The course is continued in all four directions with full blocks.

The second course begins with a through-going block (Fig. 2, block A) set exactly in the middle of the crossed wall. in this way, three cross joints are covered by the block, instead of two as in the last method (Fig. 2).

The through-going block is followed by 1/4 blocks on its ends but then the course continues in all directions with full blocks.

Try to develop more possibilities but do not forget the requirements mentioned on page **.

FOOTINGS - PLINTH COURSE - RISING LANDCRETE WALL

The illustration opposite shows what a cross junction will look like during the construction (Fig. 1).

Again, It is possible to maintain the half-block bond between the footings and the plinth course in wall I, as described on the previous pages. The bonding of the plinth course is a repetition of the bonding of the second footing course.

However, it can be seen that the half-block bond between the footings and the plinth course is not perfectly maintained in wall II. This is because of the 4 cm setting back on both sides as well as the reduced wall thickness.

The bond of the rising landcrete walls is the same as described on the previous pages. Only two courses are shown because the rest of the courses are repetitions of these two.

If you compare the bond of the rising landcrete wall with the plinth course, you will see that the half-block bond is not maintained between them. The only way it could be maintained is by cutting more blocks and changing the thicknesses of some of the joints. This would weaken the entire wall as well as wasting materials, so the Rural Builder should consider this bonding all right as it is shown here.

- REMEMBER: The rising landcrete wall is 1 cm thinner than the plinth course. Do not forget to maintain the "good" faces of the walls by laying the landcrete blocks flush with the plumbed faces of the plinth courses below.

PIERS

ATTACHED PIERS

Attached piers; also called engaged piers, wall piers, blind piers or pilasters, are piers partly sunk into a wall and properly bonded into it.

Normally the visible part of a pier projects only slightly from the wall, but in Rural Building the projection may be as much as the thickness of the wall or even more,

Formerly, attached piers were most often used as decorative elements. The Rural Builder, however, uses attached piers chiefly to strengthen walls. At the same time he saves valuable materials such as cement, reinforcement bars and timber for formwork that would be needed for a reinforced concrete pillar.

The construction of an attached pier is very similiar to that of a T-junction. The only difference is that the wall which joins the front wall is very short, and with a stopped end, thus forming an attached pier (Fig. 1).

The illustration shows that the bonds used to construct this pier are the same as those introduced in the chapter on T-junction bonds. Compare it with the text and illustrations there.

- NOTE: The plinth course is set back everywhere from the footings by 4 cm, except on the back side of the attached pier where it is set back only 3 cm (Fig. 1).

Do not forgot to build the landcrete blocks flush with the plumbed (good) face of the plinth course. This means that on the other face of the wall there will be a 1 cm set-back caused by the 1 cm difference in size between the sandcrete blocks in the plinth course and the landcrete blocks in the rising wall (Fig. 1, point A).

SIMPLE PIERS

A pier is a pillar-shape of brickwork, blockwork or stone which usually has a square or rectangular section, and supports a load. in Rural Building its mass also helps to anchor the roof structure.

The easiest way to construct a pier is by simply laying full blocks flatwise one above another (Figs. 1 & 2). This will be sufficient in situations where the pier does not have to carry a very heavy load.

The disadvantage of this construction is that any roof anchorage must be fixed to the sides of the pier.

The best way to anchor a member of the structure to a pier is through the centre of the pier.

So-called perforated blocks can be made by using a specially made wooden mould (Fig. 3). in contrast to the common type of perforated block which has many smaller holes, this type has only one large hole through its centre. It is also called an open block.

Open blocks are made by casting mortar between two frames (Fig, 4). The bigger frame is made similarly to the wooden mould described in the Reference Book, Tools section. The smaller frame is tapered and has a handle to make it easier to remove from the block.

After the pier is built, the anchoring bar is inserted in the hole and the remaining space is filled up with mortar or concrete.

FOOTINGS FOR PIERS

There are situations where piers are needed which not only have to carry heavy loads but also have to be very heavy in themselves. This is to anchor the roof against the suction of strong winds.

In order to save valuable building materials such as cement, reinforcement bars and timber, as well as to reduce the construction time, blockwork piers are often built.

There are several possible bonding arrangements. The bonds introduced in this chapter represent only a few types, but they will meet the requirements of the Rural Builder.

The type of bond which is used depends largely on which materials are available and on the size of pier which is desired.

The opposite illustrations show a bond for footings with sandcrete blocks laid flatwise. Refer to below for another footing method. Both bonds can also be used to build up an entire pier, in case a heavy duty pier is desired.

All the courses in the illustration on the left consist of a pair of blocks which are set 2 cm out of line with each other at the header sides. You can see this 2 cm difference at points A, B, C, D in Figs. 1 and 2.

This is done to maintain a square shape of 48 cm by 48 cm, since the width of the two blocks plus a joint is 48 cm, while the length of each block is only 46 cm. Since the courses cross each other, a reinforcement bar for anchorage could be built-in between the cross joints (Fig. 2, E).

BONDS FOR SANDCRETE PIERS

The following two bonds are also square-shaped but have shorter dimensions than the footing bonds: 34 cm by 34 cm.

Fig. 1 shows the best bond for a pier with the above measurements. This is because each course uses a total of lg blocks, which means that there is no waste.

The through-going cross joints in each course must be widened (Fig. 1, a & b) to 4 cm in order to obtain a width of 34 cm across the two blocks; 34 cm is the length of the 3/4 blocks.

The 3/4 block in each course is set over the 1/4 block below, and across the 4 cm joint, making an alternating arrangement as shown (Fig. 1).

Fig. 2 shows another bond for a sandcrete pier. The pier is built entirely of 3/4 blocks. The cross joints all go through and all have a 4 cm thickness.

It is obvious that this type of pier should be built only if there are a lot of 3/4 blocks left-over from another construction, because otherwise all the 1/4 blocks are left-over and wasted.

BONDS FOR LANDCRETE PIERS

The examples of bonds for landcrete piers shown on below are similar to some of the bonds already explained. Fig. 1 shows a bond which is basically the same as the footing bond on above, except the blocks are laid edgewise.

Each course consists of two full blocks laid edgewise and across the course below. in order to maintain a square shape of 30 cm by 30 cm, the blocks are set 1 cm out of line with each other at their header sides (see points A, B, C, & D).

The bonding method seen in Fig. 2 requires cutting two blocks per course and results in a rather weak bond. The builder should avoid making this type of pier except when he needs to use up some part-blocks left over from another construction .

Fig. 1 below shows another bonding method for landcrete piers with the blocks laid edgewise. This method has the advantage that an iron rod can be set into the centre of the blocks, either to reinforce the pier or to act as an anchor, or both.

- NOTE: Landcrete piers should not carry heavy loads such as a truss or a concrete beam, because they are too weak. They may be used to support and anchor overhanging rafters of a roof above a verandah.

If a landcrete pier has to carry heavy loads, its dimensions should be increased to a minimum of 55 cm by 55 cm.