brick masonry construction

8/18/2019 Brick Masonry Construction

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Brick Masonry Construction1.3


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The following information relates to the construction of brick walls to meet AS3700, the design and aesthetic

requirements.

Mortar

AS3700: 2001, Table 10.1 gives the options for mortar mixes classified as M1 to M4. M1 mortars are for

restoration applications. M2 mortars are for use in interior walls above dampcourse or in exterior walls above

dampcourse if more than one km from a body of salt water and 10 km from a surf coast and the wall has

protection from water ingress above. M3 and M4 mortars are those most commonly used in construction. Table

11 gives the proportions of the most commonly used mortars. Other deemed-to-satisfy compositions are given in

AS3700. Special mortars that are tested and shown to meet requirements are allowed with verification on site.

Note: Proportions are by volume and should be measured with a bucket or gauge box, NOT A SHOVEL.

Table 11. Typical Mortar Mixes

Bricks & Pavers Technical Manual

Section 1.3. Brick Masonry Construction 1.301

ADV03783

Refer to page 1.104 for description of Durability Class. *Methylcellulose type, not air entrainers such as detergent.

Where masonry strength is crucial, trial walls should be constructed with the bricks and mortar to be used on

the job, then tested before construction commences. Masonry bond strength is related to the suction of the

bricks, the particle size distribution of the sand, cement content, additive contents, etc. For many jobs these

panels can also be used as physical samples of the required quality of the bricklaying and cleaning.

Note: AS 3700 allows the use of:

• Cements complying with AS 3972 or AS 1316

• Lime complying with AS 1672.1

• Sand that is free of any deleterious materials

• Water that is free from deleterious materials and

• Admixtures including plasticisers, air entraining agents and set retarders complying with AS1478.1,

cellulose-type water thickeners, colouring pigments complying with BS EN 12878 and bonding polymers.t

Mortar DurabilityMix proportions by volume

Type Class Portland or Hydrated WaterBlended Cement Lime Sand Thickener*

M1 PRO 0 1 3 No

M2 PRO 1 2 9 No

M3 GP 1 1 6 No

M3 GP 1 0 5 Yes

M4 EXP 1 1 ⁄ 2 41 ⁄ 2 No

M4 EXP 1 0 4 Yes


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Mortar (continued)

No other material may be used until tests on masonry constructed with the mortar, made with the material or

admixture shows the masonry complies with the standard’s requirements for compressive strength, flexural

strength and durability.

Deleterious materials are those reducing the strength or durability of the masonry and including anything that

attacks the built-in components. This means the use of fire clay, detergent, sugar, soft drink, etc., are banned.

Most of these materials severely reduce mortar strength and durability. Water thickener must be used only

according to the manufacturer’s directions because overuse severely reduces mortar strength.

Mortar Estimator

Table 12. Estimated Material Requirements to Lay 1,000 Standard Bricks



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Mix Composition 40 kg bags 25 kg bags Cubic metres Tonnes of

(C:L:S) of cement of lime of sand damp sand

M3 1 : 1 : 6 4 2.4 0.64 1.2

M3 1 : 0 : 5 4 0 0.64 1.2

M4 1 : 0 : 4 6.5 0 0.64 1.2

M4 1 : 1 ⁄ 2 : 41 ⁄ 2 5.3 1.6 0.64 1.2

This table assumes partial filling of cores and typical site wastage.

Only make sufficient mortar for immediate use. If mortar starts to set, it may be re-tempered once only.

Where bricklaying is interrupted, the mortar should be covered to prevent evaporation and mixed with the trowel

before continuing. t


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Mortar (continued)

Mortar Colour

The mortar colour can dramatically affect the overall look. The colour of mortar is influenced by the colour of the

cement and the aggregates (sand). Many pigments are also available ranging in colour through red, yellow,

brown, green, blue and black (mainly oxides but carbon black can be used to give black mortar). The cheapest

way of colouring mortar is to use coloured sand. White and yellow sands are commonly available but red and

brown sands are also available. Sands are normally natural materials which vary considerably even in the one

deposit. To ensure colour consistency, sufficient sand from the one batch should be set aside for the whole job.

Where colour is crucial to the look of the masonry, before accepting the sand, a trial wall should be built (4 bricks

x 10 courses). After the mortar dries assess the colour. Where oxides or carbon black are used as colours never

use more than 10% by weight of the cement content.

Colours are additive in their effect and it is possible to get different shades and tones of mortar using different

combinations of cement, sands and oxides.

Table 13: Typical Coloured Mortar Components

Note: The colour of mortar can be severely degraded by incorrect or poor brick cleaning. ■



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Mortar Colour Cement Sand Oxide

Red Grey White or Yellow or Red Red

Yellow Off-white or Grey Yellow Yellow & Brown

Cream Off-white Yellow None

Tan Grey White or Yellow Brown

Black Grey Yellow Black


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Joint Types

The type of joint can dramatically affect the overall look of brick masonry. Joints can be used to create a casual,

rustic or formal look to brickwork. There are many different joints; the most common ones used in Australia are

shown below.

Terminology and joint preference differs in different countries and within Australia. Where there is any

confusion, always use a drawing or physical sample to avoid misunderstandings.

Shallow ironed joints are recommended in areas requiring exposure grade bricks and mortar. Tooling the joint to

produce ironed and struck joints is equivalent to steel trowelling concrete and produces a dense smooth surface

which sheds water and dirt better than other types of joint. Ironed and struck joints should always be used for

bricks with straight sharp edges such as Smooth Face and Velour bricks.

Raked joints may be used with any type of brick but they tend to retain dirt and may lead to streaks down the

masonry in dirty environments. Raking must not come closer than 5 mm to any core. This usually limits raking to

less than 10 mm, however it is best to check the bricks that are being used before raking. AS3700 specifies that

joints in walls in marine, severe marine or aggressive environments or on aggressive soils must be tooled to a

dense smooth surface. This precludes raking and in practice ironed joints are the only ones that consistently

meet the requirement.

Flush joints may be used with any type of brick. However, flush joints are particularly effective with rumbled

bricks as flush joints make the joints look to be of variable thickness that gives a pleasing rustic look. ■



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Flush Joint Raked Joint Ironed Joint Weathered JointStruck Joint


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Joint Sizes

Mortar bed joints are required to be less than 10 mm unless the design specifies another thickness. A different

thickness may only be specified after the designer considers the effect on compressive and flexural strength of

the masonry. During construction mortar bed joints are allowed to deviate by ± 3mm. Because of poor practice

or lack of proper direction some slabs and footings are finished at the wrong height. Mortar joints up to 50 mm

thick have been used to get the correct coursing, however, this is not allowed under AS3700.

Perpends are to have a minimum design thickness of 5 mm. In structural brickwork perpends may be up to 10 mm

thicker than the specified thickness but no thinner. In face brickwork perpends may deviate by ± 5 mm from the

average width but in any one wall the maximum difference allowable between any two perpends is 8 mm.

The preceding tolerances do not apply in the case of thin bed mortars and perpend tolerances do not apply where

perpends are not filled with mortar. ■

Weepholes

Weepholes are to allow moisture that collects in the cavity to escape. Weepholes should be spaced at less than

1200 mm centres wherever flashing is built into the masonry to shed water from the cavity. Weepholes are

usually empty perpends (10 mm wide) but proprietary products are available to prevent the entry of insects. In

high wind areas it has been known for water to be blown up the cavity onto the inner wall and as this is very

undesirable, more, narrower weepholes are usually built into the wall. It is essential that weepholes remain open

and render and other applied coatings, where used, must be raked out of the joint. ■



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Brick Estimator

Brickwork is based on the 600 mm unit, (seven courses high and two and a half bricks long). This unit fits in with

doors, windows and other building materials. The number of bricks required for a wall can be determined from

the Brick Coursing Height and Brick Gauge tables on pages 1.310-1.312 of this manual. Select the height of the

wall and from the following page for the brick height chosen determine the number of courses. From the next

page for 230 mm long bricks or the one after for 290 mm bricks, determine the number of bricks for the length of

your wall. A half brick should be calculated as 1 whole brick, due to site wastage. Multiply the number of bricks

by the number of courses to give the number of bricks for the wall. Saw cutting bricks may mean getting two

halves from a brick but this is not usual practice because of the cost of cutting. ■



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Brick bonds and other decorative effects

A bond is the pattern in which bricks are laid. The most common bond is Stretcher Bond which consists of courses

of full bricks where every course is offset half a brick from the course below. When following the mortar joint,

stretcher bond has the longest vertical pathway and therefore the best bend strength.

Stretcher bond is used in walls one brick wide. Where walls are two or more bricks wide then stretcher bond

needs ties to hold the leaves together to give it a monolithic action. To avoid the use of ties traditional practice

has been to lay some of the bricks sideways. This has usually been either full courses of headers with full

courses of stretcher (English) or courses of alternating header and stretcher (Flemish). A variation of Flemish

Bond is Garden Wall Bond where courses are made of a header and three stretchers alternating.

Corner treatment can be different in these bonds. English corners end in full stretchers or full headers, and any

part brick required to make up the course is set inside the corner. Dutch corners end in the part bricks.

Variations on these bonds are common in particular a header course every three or six courses with stretcher

courses between.

Although these bonds have traditionally been developed for thick walls, they can be used in single leaf walls as

a decorative effect using cut bricks for the headers. Such walls are usually non-load bearing. Cutting costs are

high but not excessive as the headers have the cut side turned in and the bricks can be bolstered.

Other decorative bonds may be used in non-load bearing applications, particularly in the form of panels. The

limitations are strengths lower than Stretcher Bond and the cost of cutting and slower brick laying. The

decorative effect of bonds is highlighted by using a mortar in a contrasting colour to the brick.

Other bonds include:

• Stack Bond – Bricks laid horizontally in vertical columns so all vertical joints align.

• Soldier Stack Bond – Bricks laid vertically in vertical columns so all vertical joints align.

• 1/3 Bond – Every course is offset by 1/3 of a brick.

• Zigzag Bond, Vertical Zigzag Bond, 45˚ Stretcher Bond, Chevron Bond, Basket Weave Bond, 45˚ Basket

Weave Bond and virtually any pattern that tessellates.t



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Brick bonds and other decorative effects (continued)

Other decorative effects are available such as:

• Laying bands of bricks of the same colour with different textures eg smooth faced and rock faced;

• Laying bands of bricks with different (contrasting or complimentary) colours;

• Corbelling (bricks set out from the wall);

• Racking (bricks set back into the wall);

• Quoining (corner bricks in different colours or set out from the wall);

• Soldiers above openings or as a single course;

• Copings on piers and parapet walls;

• Sills in different colours or textures, using sill bricks, etc.; or,

In the late 1800’s bricks of contrasting colours were laid in patterns such as diamonds or crosses. A more subtle

effect can be made by laying bricks with different textures or corbelling the bricks in these patterns.

Combinations of the above effects can be used. Eg. An American Architect specified a corbelled course with the

course below to be laid in the darkest bricks selected from the packs delivered. The darker band accentuated the

shadowing effect from the corbelled course. t



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Brick bonds and other decorative effects (continued)

Stack Bond Soldier Course (With Stretcher Bond)

Stretcher Bond Common Bond (Full Headers every 6th Course)

Flemish Bond Common Bond (Flemish every 6th Course)

English Cross or Dutch Bond Garden Wall Bond


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1.310


Section 1.3. Brick Masonry Construction

76mm 119mm 162mm 50mm 90mm

3000

2700

2400

2100

1800

1500

1200

900

600

300

3000mm

2700mm

2400mm

2100mm

1800mm

1500mm

1200mm

900mm

600mm

300mm

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

50

49

48

47

46

45

44

43

42

41

40

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

Brick Coursing Height


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1 230 250

11 ⁄ 2 350 370

2 470 490

21 ⁄ 2 590 610

3 710 730

31 ⁄ 2 830 850

4 950 970

41 ⁄ 2 1070 1090

5 1190 1210

51 ⁄ 2 1310 1330

6 1430 1450

61 ⁄ 2 1550 1570

7 1670 1690

71 ⁄ 2 1790 1810

8 1910 1930

81 ⁄ 2 2030 2050

9 2150 2170

91 ⁄ 2 2270 2290

10 2390 2410

101 ⁄ 2 2510 2530

11 2630 2650

111 ⁄ 2 2750 2770

12 2870 2890

12

1

⁄ 2 2990 3010

13 3110 3130

26 6230 6250

261 ⁄ 2 6350 6370

27 6470 6490

271 ⁄ 2 6590 6610

28 6710 6730

281 ⁄ 2 6830 6850

29 6950 6970

291 ⁄ 2 7070 7090

30 7190 7210

301 ⁄ 2 7310 7330

31 7430 7450

311 ⁄ 2 7550 7570

32 7670 7690

321 ⁄ 2 7790 7810

33 7910 7930

331 ⁄ 2 8030 8050

34 8150 8170

341 ⁄ 2 8270 8290

35 8390 8410

351 ⁄ 2 8510 8530

36 8630 8650

361 ⁄ 2 8750 8770

37 8870 8890

37

1

⁄ 2 8990 9010

38 9110 9130

381 ⁄ 2 9230

39 9350

391 ⁄ 2 9470

40 9590

401 ⁄ 2 9710

41 9830

411 ⁄ 2 9950

42 10070

421 ⁄ 2 10190

43 10310

431 ⁄ 2 10430

44 10550

441 ⁄ 2 10670

45 10790

451 ⁄ 2 10910

46 11030

461 ⁄ 2 11150

47 11270

471 ⁄ 2 11390

48 11510

481 ⁄ 2 11630

49 11750

491 ⁄ 2 11870

50 11990

100 23990

No. of Length OpeningBricks (mm) (mm)



No. of LengthBricks (mm)

131 ⁄ 2 3230 3250

14 3350 3370

141 ⁄ 2 3470 3490

15 3590 3610

151 ⁄ 2 3710 3730

16 3830 3850

161 ⁄ 2 3950 3970

17 4070 4090

171 ⁄ 2 4190 4210

18 4310 4330

181 ⁄ 2 4430 4450

19 4550 4570

191 ⁄ 2 4670 4690

20 4790 4810

201 ⁄ 2 4910 4930

21 5030 5050

211 ⁄ 2 5150 5170

22 5270 5290

221 ⁄ 2 5390 5410

23 5510 5530

231 ⁄ 2 5630 5650

24 5750 5770

241 ⁄ 2 5870 5890

25 5990 6010

251 ⁄ 2 6110 6130

Brick Gauge

230 mm Long Bricks


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1.312


Section 1.3. Brick Masonry Construction

1 290 310

11 ⁄ 3 390 410

12 ⁄ 3 490 510

2 590 610

21 ⁄ 3 690 710

22 ⁄ 3 790 810

3 890 910

31 ⁄ 3 990 1010

32 ⁄ 3 1 090 1110

4 1190 1210

41 ⁄ 3 1 290 1310

42 ⁄ 3 1 390 1410

5 1490 1510

51 ⁄ 3 1 590 1610

52 ⁄ 3 1 690 1710

6 1790 1810

61 ⁄ 3 1 890 1910

62 ⁄ 3 1 990 2010

7 2090 2 110

71 ⁄ 3 2 190 2210

72 ⁄ 3 2 290 2310

8 2390 2410

81 ⁄ 3 2 490 2510

82 ⁄ 3 2 590 2610

9 2690 2710

91 ⁄ 3 2 790 2810

92 ⁄ 3 2 890 2910

10 2990 3010

101 ⁄ 3 3090 3110

102 ⁄ 3 3190 3210

11 3290 3310

111 ⁄ 3 3390 3410

112 ⁄ 3 3490 3510

12 3590 3610

121 ⁄ 3 3690 3710

122 ⁄ 3 3790 3810

13 3890 3910

131 ⁄ 3 3990 4010

261 ⁄ 3 7890

262 ⁄ 3 7990

27 8090

271 ⁄ 3 8190

272 ⁄ 3 8290

28 8390

281 ⁄ 3 8490

282 ⁄ 3 8590

29 8690

291 ⁄ 3 8790

292 ⁄ 3 8890

30 8990

301 ⁄ 3 9090

302 ⁄ 3 9190

31 9290

311 ⁄ 3 9390

312 ⁄ 3 9490

32 9590

321 ⁄ 3 9690

322 ⁄ 3 9790

33 9890

331 ⁄ 3 9990

332 ⁄ 3 10090

34 10190

341 ⁄ 3 10290

342 ⁄ 3 10390

35 10490

351 ⁄ 3 10590

352 ⁄ 3 10690

36 10790

361 ⁄ 3 10890

362 ⁄ 3 10990

37 11090

371 ⁄ 3 11190

372 ⁄ 3 11290

38 11390

38

1

⁄ 3 11490

382 ⁄ 3 11590

39 11690

391 ⁄ 3 11790

392 ⁄ 3 11890

40 11990

401 ⁄ 3 12090

402 ⁄ 3 12190

41 12290

411 ⁄ 3 12390

412 ⁄ 3 12490

42 12590

421 ⁄ 3 12690

422 ⁄ 3 12790

43 12890

431 ⁄ 3 12990

432 ⁄ 3 13090

44 13190

441 ⁄ 3 13290

442 ⁄ 3 13390

45 13490

451 ⁄ 3 13590

452 ⁄ 3 13690

46 13790

461 ⁄ 3 13890

462 ⁄ 3 13990

47 14090

471 ⁄ 3 14190

472 ⁄ 3 14290

48 14390

481 ⁄ 3 14490

482 ⁄ 3 14590

49 14690

491 ⁄ 3 14790

492 ⁄ 3 14890

50 14990

100 29990





132 ⁄ 3 4090 4110

14 4190 4210

141 ⁄ 3 4290 4310

142 ⁄ 3 4390 4410

15 4490 4510

151 ⁄ 3 4590 4610

152 ⁄ 3 4690 4710

16 4790 4810

161 ⁄ 3 4890 4910

162 ⁄ 3 4990 5010

17 5090 5110

171 ⁄ 3 5190 5210

172 ⁄ 3 5290 5310

18 5390 5410

181 ⁄ 3 5490 5510

182 ⁄ 3 5590 5610

19 5690 5710

191 ⁄ 3 5790 5810

192 ⁄ 3 5890 5910

20 5990 6010

201 ⁄ 3 6090 6110

202 ⁄ 3 6190 6210

21 6290 6310

211 ⁄ 3 6390 6410

212 ⁄ 3 6490 6510

22 6590 6610

221 ⁄ 3 6690 6710

222 ⁄ 3 6790 6810

23 6890 6910

231 ⁄ 3 6990 7010

232 ⁄ 3 7090 7110

24 7190 7210

241 ⁄ 3 7290 7310

242 ⁄ 3 7390 7410

25 7490 7510

251 ⁄ 3 7590 7610

25

2

⁄ 3 7690 7710

26 7790 7810

Brick Gauge

290 mm Long Bricks


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Blending

Raw materials for brick making are from natural sources and these vary in colour within any one deposit. Brick

makers blend materials to moderate the colour variation but it still occurs. Colour variation may be caused by

different conditions across the kiln. No matter how well made, bricks delivered to site will have some degree of

colour variation.

Poorly blended bricks may show unwanted patches, streaks and bands of colour in the finished masonry.

To avoid this:

• All bricks required for the project, or as many packs as will fit, should be delivered at one time and stored

on site; and,

• Bricks should be drawn from at least four packs simultaneously, working down from the corners of each

pack. ■

Brick Storage

Bricks stored on site should be covered and kept off the ground. Bricks may absorb ground water containing salts

or coloured minerals creating subsequent problems with staining. Bricks when laid saturated usually produce

excessive efflorescence as the masonry dries. Saturated bricks may also adversely affect the mortar bond

strength.

Moving bricks around the site may cause chipping and excessive movement of packs should be avoided. ■



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Laying Practices

The following practices are recommended:

• Mortar, extruded from tapping the brick down to the string line, should be cut off with an upward stroke of

the trowel. In this manner, a clean cut is made, without smearing the face of the brick.

• Joints should be tooled progressively as the bricks are laid, when the mortar is firm to thumb pressure. High

suction bricks require joints to be tooled more frequently than low suction bricks. Tooling too late produces

a ‘burned’ joint, where the surface may not be smooth and dense.

• After allowing the mortar to undergo initial set, within a day, dry brush mortar smears, to remove any dags,

and then wet brush any remaining mortar stains. Mortar that is allowed to set on the masonry face may

require high-pressure water jet cleaning or more costly, risky methods of cleaning.

• Cavities should be kept as clear as possible from mortar droppings. Flushing out the cavity removes

inadvertently dropped mortar and ensures ties are clean and flashing and damp proof courses are not

bridged. It is poor practice and usually ineffective to flush large quantities of dropped mortar from cavities.

Usual practice is for the bricklayer to leave out one or more bricks at the base of the wall above a flashing

or the damp proof course for the washings to come out. Washings can cause serious staining where they

run down over lower brickwork and should be rinsed off thoroughly each day.

• Scaffolding should be kept at least 150 mm from the face of the brickwork to prevent a build up of mortar

droppings against the masonry.

• When bricklaying is interrupted by rain or rain is expected overnight, masonry should be protected by

covering it. Saturated masonry will produce excessive efflorescence and may lead to staining with some

bricks.

• Face bricks are supplied with one face and one header suitable for exposing (i.e. to be seen after laying).

Face bricks with unwanted marks, chips or cracks on a header should be laid with that header inside a

mortared joint. Face bricks with unwanted marks, chips or cracks on the face should be set aside by the

bricklayer (or labourer) for use as commons. Boral will not be responsible for replacing bricks with unwanted

marks, chips or cracks that have been laid. ■



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Control Joints

Control joints must not be bridged by mortar or render. After laying the bricks or rendering, the joint must be

cleaned. Lumps of mortar or render can transfer forces across the closing joint and will cause the bricks to crack

(or spall). Control joints are usually constructed with a highly compressible material (in the form of a sheet or

rod) inserted to keep dirt and moisture from penetrating to the cavity. For aesthetic reasons a compressible

caulking material, matched to the mortar colour, is usually applied on the outside. As the joint closes,

compressible caulking compounds may be extruded from the joint but incompressible ones may damage the

bricks. If extruded caulking compound is considered unsightly, it can be cut out and replaced or the compound

can be recessed during construction. Care must be taken when choosing a caulking compound to ensure it is a

highly compressible type that will survive for the design life of the building and not discolour significantly. There

are numerous suitable materials available and manufacturer’s recommendations should be sought.

Where a control joint has flexible masonry ties built in, a piece of the compressible material must be removed to

accommodate the tie. ■

Damp Courses and Flashing

Membrane type damp proof courses (DPC) must be laid across the full width of the wall or leaf and must project

through the mortar on either side and be completely visible after laying and cleaning is complete. Recessing DPC

below the edge of the brickwork so that the mortar bridges the DPC invalidates its use and is therefore entirely

unacceptable. Bridged DPC may lead to rising damp, salt attack and or accelerated corrosion of the built-in

components that may lead to structural failure. Recessing flashing below the mortar although common is not

good practice as it allows the water that should be shed to soak into the wall below the flashing.

DPC and flashing at the base of a wall may be combined. Lengths should be as long as possible but where not

continuous, two adjacent pieces should overlap by at least 150 mm and if possible be sealed together. If a

termite shield is used in the same joint as the DPC, the DPC material must be compatible with the termite shield

or corrosion may destroy the DPC.

General practice has been to recommend that flashings and DPCs be sandwiched between the mortar. There is

some evidence that the common practice of laying flashings and DPC directly on the lower course of bricks and

placing the mortar on top may be superior in some instances. ■



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Cleaning of Clay Masonry

The Basics of Brick Cleaning

The cleaner the bricklayer leaves the wall, the easier will be the cleaning task. The majority of the mortar

residues and smears should be cleaned before they set hard. However, in most cases some additional cleaning

will be required to completely remove the mortar residue.

Cleaning techniques may involve high-pressure water jet equipment or hand methods. Whatever technique is

used, the following requirements must be observed to ensure additional staining problems are avoided.

Test Areas

Testing in one or more small areas is the safest way to determine the correct technique and chemical solution to

remove mortar residues. This must occur well before final cleaning, as it will usually not be possible to assess

the effectiveness of the test clean until the masonry dries.

Clean Soluble Salt Deposits First

Efflorescence, a white ‘fluffy’ deposit, cannot be removed by water or acid. Dry brushing to remove the

efflorescence before washing is recommended. If efflorescence is wetted, the salts go into solution and are

drawn back into the brickwork and will reappear as the masonry dries. Efflorescence will eventually disappear

through natural weathering.

Vanadium salts produce a green or yellow efflorescence or stain (mainly seen on cream and light coloured clay

bricks). Hydrochloric acid will make these stains much worse and may make them impossible to clean. Mild

vanadium stains may be treated with sodium hypochlorite (household bleach). Spray or brush on dry brickwork

and leave until the stain disappears, then rinse off. Proprietary mould cleaners containing sodium hypochlorite

and sodium hydroxide can be used as above and have been found very effective. Proprietary brick cleaners may

also be effective and should be used only according to the manufacturer’s instructions. Proprietary cleaners

usually contain acids that must be neutralised after use with a solution of 15 grams of washing soda

per litre of water.

More than one chemical application may be required and the walls should be rinsed thoroughly after each

treatment.t



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Cleaning of Clay Masonry (continued)

High Pressure Cleaning

High-pressure water washing is now common for cleaning brickwork. If used the pressure must be kept below

1000 psi (7000 kPa), the nozzle must be kept 500 mm from the brick face and the nozzle must be a wide fan jet

type with an angle of 15 degrees.

The following practices must be observed:

• Cleaning should not start until the mortar has hardened.

• Hard lumps or persistent smears should be removed by hand.

• Mask adjacent materials.

• Do not apply the acid with the high-pressure sprayer. Use a low-pressure spray or broom it on.

• Clean from top to bottom in small sections.

• Work in the shade, ahead of the sun, if possible.

• DO NOT USE EXCESSIVE PRESSURE OR GET TOO CLOSE, as this will damage the face of the brick and the

mortar joint. Mortar joints that are no longer smooth with sharp edges is a clear sign of excessive pressure.

Excessive pressure is used to make cleaning faster; it does not do a better job of cleaning. t



ADV03799


19/21


Saturate the Wall Surface

Failure to completely saturate the surface of the wall is in itself a major cause of cleaning stains. Cleaning

solutions containing dissolved mortar particles and acids will be drawn into a dry masonry wall, causing staining.

Furthermore, saturating the surface of the wall keeps the acid solution on the face of the masonry where the

mortar smears are present. It is not true that face saturation weakens the acid and slows the cleaning.

Water should be trained on the wall until the brick suction is exhausted. The area to be cleaned must be

saturated as well as all brickwork areas below. If the wall appears to be drying on the surface, reapply water

until ready to apply the cleaning solution.

Recommended acid strengths are based on application to a surface saturated wall.

Note: This point must be strictly adhered to for bricks manufactured in Queensland. Their raw materials contain

large amounts of iron oxide and failure to saturate the surface of the wall allows acid solutions to react

with the iron oxide and create severe iron oxide staining. Failure to saturate the surface of the bricks

manufactured in other parts of Australia can also lead to the acid reacting with iron oxide but to a much

lesser degree. This form of staining is known as acid burn and is particularly visible on light coloured

bricks. Acid absorption into bricks can also lead to vanadium and manganese staining. t



ADV03800


20/21


Acids – The Basics

The traditional masonry-cleaning chemical is hydrochloric acid, (also known as muriatic acid or spirits of salts).

Its main function is to dissolve the cement in the mortar mix. It has few other uses and in many stain situations

should not be used.

Hydrochloric acid is a corrosive S6 poison and care must be taken when using it. If acid is splashed onto the skin

it should be immediately swabbed with clean water, or more effectively, with a solution of bicarbonate of soda

in water, which will neutralise the acid.

The recommended acid strength for light coloured clay bricks is 1 part acid to 20 parts water and for other bricks

is 1 part acid to 10 parts water. Acid takes time to dissolve the cement and should be left on for 4-6 minutes (or

longer if needed) before washing off. After washing a solution of 15 g per litre of washing soda or 24 g per litre

of sodium bicarbonate should be sprayed on to neutralise any remaining acid. Excess hydrochloric acid will

eventually evaporate from the brickwork, however, it is likely to cause staining of the bricks and damage to

built-in components. Other acids such as sulfuric acid or nitric acid will not evaporate and are not used in

brick cleaning.

Note: The recommended strength must be strictly adhered to. Bricks manufactured in Queensland may contain

large amounts of iron oxide and the use of acid solutions stronger than 1 part acid to 20 parts water can

dissolve these particles and create iron oxide staining. For light coloured bricks manufactured elsewhere

the use of solutions stronger than 1 part acid to 20 parts water can lead to acid burn.

Proprietary masonry cleaning solutions containing a mixture of acids are available. If used, the manufacturer’s

recommendations must be strictly adhered to. Excessive and incorrect use of some proprietary cleaning solutions

has in the past, produced very bad staining.t



ADV03801


21/21


Safety Precautions

All masonry-cleaning acids are dangerous. Acids that do not dissolve cement as quickly as hydrochloric acid are

not necessarily safer and can be very much more dangerous to human health. To avoid personal injury:

• Wear goggles, gloves and protective clothing.

• Always pour acids into water – this avoids splashes of highly concentrated acid onto the operator.

• If splashed onto the body, wash with clean water and if possible, neutralise with a mixture of bicarbonate

of soda and water.

• The manufacturer’s instructions and safety precautions must be strictly adhered to if proprietary cleaning

products are used. ■



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