41 • SOLID MASONRY CONSTRUCTION Solid masonry construction includes the methods of construction used to erect buildings that use brick, block and natural stone as primary load bearing components in the form of walls. Mud brick (adobe), rammed earth (pise) and concrete could also be considered to fit this description, but this book will not attempt to deal with these relatively specialised low volume building methods, which are well catered for in specialised text books. The use of solid masonry construction in Australia dates back to the early days of European settlement, when the good qual ity Sydney sandstone and locally made sand stock bricks were used to build build ings closely modelled on those being built in Europe, particularly England. Bricks are one of the most durable build ing materials used by man and are suffi ciently flexible to meet the demands of strength and aesthetics required for house construction. Over the generations in Australia, however, the cost to build an all brick house has escalated until timber frame, or more especially brick veneer houses are so much cheaper except in a couple of localities notably Western Australia and to a slightly lesser extent South Australia and Tasmania. There are many people who strongly believe there is no alternative to a solid masonry house, as they feel the mass of the structure gives a greater sense of secu rity and well being, less noise transmission and white ant proof. All this is true, but they are generally more expensive to build than alternative timber framed houses, and are often less flexible in layout, harder to insu late and prone to cracking in reactive foun dation areas.
Masonry materials Bricks, blocks and natural stone have been covered under brick veneer construction. Traditionally, bricks used for structural walls have been of the pressed type as they are generally stronger and easier to cut than extruded-wire cut bricks. In residential con struction, the ultimate strength of the bricks is seldom tested and many extruded bricks are used in load bearing applications, as are silica-lime bricks and concrete blocks. Few houses are built of solid natural stone today, but there are still a considerable number of homes which combine a load bearing brick substructure with a natural brick facing to the outside of the house. Limestone and sandstone are easily cut and dressed to form well finished blocks, and good deposits of these stones are still being worked in NSW and South Australia. Blue stone, a form of basalt, is used in Victoria, and is a very hard stone that is dif ficult to dress and mould. In the country, bush or field rocks have been used to build houses. Although the rocks are cheap the mortar to fill the irregu lar joints between them can be excessive both in cost and in spoiling the appearance
128
of the walls. Bush rock is generally suitable as a facing only and the substructure should be of brick or post and beam, so that there is no imposed load on the bush rock wall.
Building with masonry The most important part of any masonry wall is to establish a stable and adequate foundation/footing system, because masonry walls are only as strong as the foundation/footing system that supports them. Once an adequate foundation/footing is achieved then the next step is to bring the masonry up in a uniform manner. It is gen erally poor practice to build sections of a building higher than other sections. When laying masonry, bond the individual units solidly one to the other by the prescribed method of overlapping the bricks. Most masonry work used in Australian houses consists of either a single thickness brick wall or walls that are a combination of two single brick thick skins, the latter com monly referred to as a cavity wall. This use of mainly single brick skins means the com mon or stretcher bond is the most suitable. Special complex bonding methods have been developed for brick walls that are two or more bricks thick. These are seldom used in residential construction-even when thicker walls are required, simplified meth ods of skin bonding are used, such as brick course reinforcing or galvanised steel ties. Windows and doors need lintel beams over them, except in the case of the out side skin of a cavity wall used in a brick sin gle storey cottage. In most cavity walls, only the inside skin is structural, the exter nal skin acts as a cladding to keep the weather out. Lintel beams can be steel or concrete, or structural arches can be used to bridge openings. Steel lintels are commonly cut from rolled steel bar, angle or channel, and in most instances galvanising is applied to the lintel to inhibit corrosion and eventual failure. Concrete lintels were very popular for a time before WW2 but are little used today except in special applications. The correct installation of damp proof courses in solid masonry buildings is essential. It is the protection against rising damp and other moisture induced building deterioration.
ral stone quoins or anything your imagina tion, and a sneak look at some history of architecture texts, can conjure up. Polychrome A number of colours of brick generally in a pattern. An engaged pier, often Pilaster decorated. The base of the building. Plinth The brick, block or stone Quoin that shows its face and head at the outside corner of a masonry wall.
1 . Extruded wire cut brick
2. Pressed brick
3. Queen closer brick or_ brick .,,,,,,--
f-, I
�
'1I _,,,
l._,
---�
4. Half batt
For something a little different Modern brickwork is identified with bland, single colour, dead flat stretcher bond walls. For those of you who think this is boring, take yourself off to one of the brickworks, there is at least one in most of Australia's capitals-excluding Canberra-that still produce squint, bull nose, cant, plinth and other assorted shaped bricks. You may be able to design into the walls of your solid masonry house polychrome bricks, engaged pilasters, projecting plinths, natu-
6. Bevelled closer
7. Mitred closer
SOLID MASONRY CONSTRUCTION • 41 DETAIL-COMPONENT ASSEMBLY OF AN ALL BRICK CAVITY WALL COTTAGE
Flooring within each room
Reinfarced concrete strip footings under all brick walls Crawl space and ventilation opening between 'rooms' at below floor level
Internal walls 1n some localities use 'brick on edge' for internal skin of cavity wall and for internal walls
Cavity filled with weak concrete to ground line
Reinforced concrete strip footing
DETAIL-CAVITY BRICK BASE CONSTRUCTION
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41 • SOLID MASONRY CONSTRUCTION COMMON BRICK JOINTS
-- ceding Joist top plate (pitching plate)
�:,3\. Recessed
wall cavity tie weep hole Note: Plasterboard sheeting can be fixed to internal brick skin with adhesive - this el1m1nates rendering
,,____ Door frame
terrazzo threshold
t:�
._�..... ...-:... ... Rough raked -=
·:-��-... : ,-�'):.'. -':
/',-,: ;: ' . :. : Keyed ;·.:., .
ant capping engaged pier
corbel course weep hole
EXAMPLES OF BRICKWORK TIES �y duty galvanised 1 � - �t::rcavity tie
concrete filled cavity (to ground level)
•
___ Reinforced concrete strip footing
2. Frame (window and door) tie, with or without twist
•
DETAIL SECTION-TRADITIONAL CAVITY BRICK WALL cavity tie
Welded mesh
Expanded metal mesh
� vanised wire veneer tie
Woven wire mesh
BRICKWORK BED REINFORCING 130
�lvanised wire cavity tie
SOLID MASONRY CONSTRUCTION • 41 SPECIAL BRICKS LIMITED AVAILABILITY
DETAIL-ELEVATION OF STEEL ANGLE LINTEL
STEEL LINTELS
DETAIL-OPENING HEAD
Single bullnose stop
Steel angle, galvan1sea 1f possible
DETAIL-LINTEL FOR BRICKWORK
Plinth (corner splay)
Bullnose return
end
Precast beams incorporating self flashing are sometimes available 131
41 • SOLID MASONRY CONSTRUCTION Arches Arches have been used by masons to span _:_�..u.u.1-- --'-� openings from prehistoric times and are \\ I . thought of by many people as the applicable \ . 1 )\I/ head to openings in masonry walls today. Arches use gravity, the force that acts downwards to lock together the units of the arch. The arch will remain supporting until the ability of the walls on each side of the arch to withstand the outward pressure, exerted by the force of . I \ \ ·1 / gravity trying to flatten the arch, is exceeded. \ I Therefore the rules of thumb which allow /\i.l/ _j_�, arches to remain structurally sound are: the greater the curve the stronger the arch; the more solid the opening of the supporting wall the more stable the arch. Arches are built on a removable form or 'cen tre'. That is, the bricklayer or mason builds the arch onto a supporting structure the same shape as the arch will be when completed. Brick and block arches have one, two or three rings generally of the standard masonry unit. Sometimes specially-made tapered brick or block units are manufactured, but this practice is seldom applied these days. Stone arches, because of the larger size of unit being used, generally only have one ring and each unit is cut COMMON ARCH TYPES to a tapered voussoir. Flat arch In brick and concrete block walls it is advis Segmental arch able to build brick course reinforcing into the Semi-circular or Roman arch courses immediately above the arch. 1·
/
CQMMON CONCRETE BLOCK BOUNDS
4
COMMON BRICK BONDS
i
390
1111(
1 90
Stretcher
t
1111(
390
)lr
190
Stack
1111(
1 90
..
Vertical staggered
390 •
•
i
0 4
t 190 Mixed full and half height blocks-stretcher
Stretcher bond-cavity brick wall
English bond-230 brick wall
t
1111(
390
190
Ribbed blocks-stretcher
1 90
1111(
Modified Flemish bond (garden wall) -230 brick wall
132
American brick-stretcher
..
•
SOLID MASONRY CONSTRUCTION • 41
Steel lintels. Lintel may be articulated with a soldier course or concealed
J___l_Ll._-L-,LJ_
Concrete lintels. Lintel exposed
L-
waII or roof load above wall load area
Arching action of masonry above opening supports weight of wall outside of wall load triangle
Lintel carries less wall load than normal wall load triangle
Horizontal thrust resulting from any arching action must be resisted by the wall mass on either side of the opening
Lintel must carry additional loads 1f concentrated loads and floor or roof loads fall within normal wall load triangle
LOADED BRICKWORK
J
UNDERSTANDING BRICKWORK LINTELS
J
l �
-�
'-.
GLASS BLOCKS 133
41 • SOLID MASONRY CONSTRUCTION DETAIL SECTION-CONCRETE BLOCK COTTAGE WALL
------
-----------.
�----
metal cleat fixed to rafter/plate for high wind conditions
COMMON CONCRETE BLOCKS CONSTRUCTION DETAIL
Bond beam, special hollow concrete blocks for top course, have reinforcing steel and concrete fill to bond wall and act as a lintel
This single skin form 1s not approved in some regions, particularly where there are wet winters
plywood flooring
floor J01st
/
bearer/
ant cap and strip
,--,..+--�'monsoon' tie (optional) for high wind areas
special corner block 90 X 90 X 190
engaged pier
reinforced concrete strip footing
0
a
90 140 190 240 290 390
b
C
90 190 290 390
40 90 190
Plus I 0mm for mortar JOlnt
STANDARD METRIC BLOCK SIZES 134
SOLID MASONRY CONSTRUCTION • 41 COMMON STONE WALLS
Random rubble
courses
mortar fill
Coursed rubble
galvanised steel angle to allow resistance to overturn1ng, but allow vertical movement
to allow bonding but to accommodate
Coursed ashlar
mast1
brick reinforcing mesh
Random ashlar
135