Upload
luis
View
242
Download
1
Embed Size (px)
Citation preview
8/18/2019 Brick Masonry Construction
1/21
Brick Masonry Construction1.3
8/18/2019 Brick Masonry Construction
2/21
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
8/18/2019 Brick Masonry Construction
3/21
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
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.302
ADV03784
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
8/18/2019 Brick Masonry Construction
4/21
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.303
ADV03785
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
8/18/2019 Brick Masonry Construction
5/21
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.304
ADV03786
Flush Joint Raked Joint Ironed Joint Weathered JointStruck Joint
8/18/2019 Brick Masonry Construction
6/21
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.305
ADV03787
8/18/2019 Brick Masonry Construction
7/21
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.306
ADV03788
8/18/2019 Brick Masonry Construction
8/21
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
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.307
ADV03789
8/18/2019 Brick Masonry Construction
9/21
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
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.308
ADV03790
8/18/2019 Brick Masonry Construction
10/21
ADV03791
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.309
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
8/18/2019 Brick Masonry Construction
11/21
ADV03792
1.310
Bricks & Pavers Technical Manual
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
8/18/2019 Brick Masonry Construction
12/21
ADV03793
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.311
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 Length OpeningBricks (mm) (mm)
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
8/18/2019 Brick Masonry Construction
13/21
ADV03794
1.312
Bricks & Pavers Technical Manual
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
No. of Length OpeningBricks (mm) (mm)
No. of Length OpeningBricks (mm) (mm)
No. of LengthBricks (mm)
No. of LengthBricks (mm)
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
8/18/2019 Brick Masonry Construction
14/21
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.313
ADV03795
8/18/2019 Brick Masonry Construction
15/21
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.314
ADV03796
8/18/2019 Brick Masonry Construction
16/21
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.315
ADV03797
8/18/2019 Brick Masonry Construction
17/21
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
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.316
ADV03798
8/18/2019 Brick Masonry Construction
18/21
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
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.317
ADV03799
8/18/2019 Brick Masonry Construction
19/21
Cleaning of Clay Masonry (continued)
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
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.318
ADV03800
8/18/2019 Brick Masonry Construction
20/21
Cleaning of Clay Masonry (continued)
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
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.319
ADV03801
8/18/2019 Brick Masonry Construction
21/21
Cleaning of Clay Masonry (continued)
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. ■
Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction 1.320