Materials architects builders pdf

Under most conditions it disappears without deleterious effect within one year. The criteria for general use, damp-proof courses and engineering use are set out in Table 1. Water absorption and suction The level of water absorption is critical when bricks are to be used for damp-proof courses, or as engineering bricks. Appropriate limits are shown in Table 1.

Suction rates are now quoted by most brick manufacturers, as high values can adversely affect the bricklaying process. Generally low or medium suction rates 1. Subsequent moisture and thermal movements are largely reversible, and movement joints allowing for a 1 mm movement per 1 m of brickwork should be allowed, typically at 10—12 m centres and at a maximum of 15 m, in restrained walls.

Unrestrained or lightly restrained walls should have movement joints at 7—8 m centres. Horizontal movement joints should be at approximately 12 m intervals, as the vertical movement is of the same order as movement in the horizontal direction. In external unreinforced non-load-bearing walls a maximum spacing of 15 m between vertical movement joints is permitted NA to BS EN For many buildings the necessary movement joints can be made inconspicuous by careful detailing or featured as part of the design.

Appropriate locations for movement joints would be where differing structural forms adjoin, such as abutments between walls and columns or where the height or thickness of a wall changes; alternatively, at design details such as brickwork returns, re-entrant corners or the recesses for downpipes.

Using bricks with an average thermal conductivity of 0. Impact sound absorption by brickwork over the normal frequency range is fairly low and further decreased by the application of dense plaster or paint. However, the application of acoustic plasters or the addition of an independent panel of plasterboard backed by absorbent material improves impact sound insulation. These require manufacturers to document all their operational procedures and set out standards to which products must adhere.

Quality is controlled by a combination of an internal self-monitoring system and two to four independent spot-check reviews per year. Both the content of the technical literature and the products themselves are subjected to this scrutiny. Acoustic properties Good-quality brickwork is an effective barrier to airborne sound, provided that there are no voids through the mortar for the passage of sound.

Earth bricks require only low energy input for drying and have high potential recyclability. They have the advantage of inhibiting condensation and regulating the relative humidity of the internal environment. Compressive strengths are in the range 2. Reclaimed clay bricks Reclaimed bricks are often selected for aesthetic reasons, but their appearance is not a guarantee of durability.

However, the strength and water absorption properties of reclaimed bricks are usually appropriate for domestic-scale construction. Reclaimed paving bricks that have previously been exposed to frost will normally be durable, but walling bricks may not be durable when used as pavers. The overall effect can be to emphasise as a feature or reduce to a minimum the impact of the bonding mortar on the bricks. Additionally, the use of polychromatic brickwork with complementary or contrasting colours for quoins, reveals, banding and even graphic designs can have a dramatic effect on the appearance of a building.

The three-dimensional effects of decorative dentil courses and projecting corbelled features offer the designer further opportunities to exploit the effects of light and shade. Curved brickwork constructed in stretcher bond shows faceting and the overhang effect, which is particularly accentuated in oblique light.

With small-radii curvatures, the necessary change of bonding pattern to header bond can also be a visual feature, as an alternative to the use of curved-radius bricks.

The mortar, which matches the external coral-red brickwork, reduces the visual impact of the individual bricks, giving the effect of planes rather than walls.

This is relieved by the colour and shadow effects of the polychromatic and corbelled features, which are incorporated in the ventilation grilles and towers. The special bricks, cill details and banding are picked out in a deeper cadmium red and silver buff to contrast with the characteristic Leicestershire red-brick colouring.

Mortars The mortar in brickwork is required to give a bearing for the bricks and act as a sealant between them. Mortars should be weaker than the individual bricks, to ensure that any subsequent movement does not cause visible cracking of the bricks, although too weak a mix would adversely affect durability of the brickwork.

Suitable alternatives to Portland cement are listed in Table 1. When the mix is gauged by volume, an allowance has to be made for bulking of damp sand. A typical 1 : 1 : 6 cement : lime : sand mix M4—designation iii would generally be appropriate and durable for low-rise construction, but for calculated structural brickwork or for increased resistance to frost in exposed situations a greater-strength mortar may be Table 1. For prescribed mortars a combination of the constituent proportions and the day compressive strength is required.

In the repointing of old brickwork it is particularly important to match the porosity of the brick to the water-retention characteristics of the mortar. This prevents excessive loss of water from the mortar before hydration occurs, which may then cause the pointing to crumble.

The recycling of bricks is not possible, except as rubble, when strong Portland cement mortar is used. The majority of the particle size distribution should lie between the stated limits. Designations to BS Ideally, brickwork should be designed to ensure the minimal cutting of bricks and built with a uniform joint width and vertical alignment of the joints perpends.

During construction, brickwork should be kept clean and protected from rain and frost. For repointing existing brickwork, it is necessary to match carefully the mortar sand and use lime mortar where it was used in the original construction. Bonding Figure 1. The stretcher bond is standard for cavity walls and normally a half-lap bond is used, but an increase in horizontal emphasis can be achieved by the less standard quarter or third bond.

In conservation work it may be necessary to use half bricks snap headers to match the appearance of bonding in solid brick walls. For one-brick-thick walls more variations are possible; most typical are the English and Flemish bonds. The equivalent English and Flemish garden wall bonds, which have more stretchers, are primarily used for one-brick-thick walls where the reduced number of headers makes it easier to build both sides fairfaced.

Panels of herringbone brickwork raking bond , or dog tooth and dentil courses as in Victorian brickwork, can generate interesting features.

In all cavity brickwork, wall ties manufactured from galvanised steel, stainless steel or polypropylene to BS EN should be incorporated Fig. Wall ties are categorised as Types 1 to 4 to BS according to their strength and appropriate use, and lengths are dependent on the cavity width Table 1.

The Building Regulations refer only to types A and B. An estimated minimum service life of 60 years is recommended by the publication DD Where mortar bed-joints do not co-ordinate between masonry leaves, slope-tolerant cavity wall ties must be used. In all cases the cavity, insulation and ties should be kept clear of mortar droppings and other residues by using a protective board.

Screw-in wall ties are available for tying new masonry to existing walls. Suitable for most masonry construction except where large differential movements are anticipated. Type 2—Masonry: General purpose. Suitable for construction up to 15 m above ground level, when built of double leaves of similar thicknesses in the range 90— mm.

Type 3—Masonry: Basic. Type 4 — Masonry: Light duty. Suitable for dwellings up to 10 m in height, when built of double leaves of similar stiffness and thicknesses in the range 90— mm. Suitable for most internal separating cavity walls. A minimum embedded length of 50 mm is required in each leaf. Wall ties in leaves of 90 mm or more should be placed at a minimum density of 2. Thinner walls require increased provision.

Occasionally, black mortars may bloom due to lime migration to the surface. Coloured mortars can be used creatively to enhance the visual impact of the brickwork and even create designs on sections of otherwise monochromatic brickwork. Through-body colours are generally more durable than surface applications.

It is important that the main criterion should be the shedding of water to prevent excessive saturation of the masonry, which could then deteriorate. Normally the brickwork is jointed as the construction proceeds. This is the cheapest and best method as it gives the least disturbance to the mortar bed.

This is only appropriate when the desired visual effect cannot be obtained directly by jointing; for example, when a complex pattern of coloured mortar joints is required for aesthetic reasons. The square recessed raked joints articulate the brickwork by featuring the joint, but these should only be used with durable, F2, S2 high-absorption bricks under sheltered conditions; furthermore, the recess should be limited to a maximum depth of 6 mm.

The struck or weathered joint also accentuates the light and shade of the brickwork, while, as a tooled joint, offering good weather resistance in all grades of exposure. Reinforced brickwork Reinforcement may be introduced vertically or horizontally into brickwork Fig.

Vertical reinforcement is possible in the cavity or in pocket-type walls, where the void spaces are formed in the brickwork, then reinforcement and concrete is introduced after the masonry is completed. Care should be taken in the use of vibrators to compact the concrete within new masonry. Decorative brickwork Tile-bricks replicate the visual effect of hung tiles. The bricks are laid in 10 mm mortar which is cut back 15 mm from the front face, using only a 1 mm vertical joint so that the tiles appear to butt joint.

The brickwork must be completed in courses ahead of the blockwork to ensure that internal vertical joints are sealed. The tile-bricks are typically used for gable-ends on housing. Plaques, motifs, murals and sophisticated sculptures Fig. For repetitive units, the clay is shaped in an appropriate wooden mould.

For large brickwork sculptures, the whole unit may be built in green bricks, with allowances made for the mortar joints and drying contraction. Thus the joint becomes only a shade line and the visual effect of the wall is totally determined by the colour and texture of the bricks.

Because the glue-mortar is stronger than traditional mortar and has tensile properties, the brickwork patterns are not constrained to standard stretcher bonding. The glue-mortar is applied in two lines to both the horizontal and vertical joints, and therefore solid or perforated bricks rather than frogged bricks are most appropriate.

Thin-bed masonry wall ties and special aramid bed-joint reinforcement are used as appropriate. Preassembled brickwork Fig. Photograph: Courtesy of Baggeridge Brick Plc. The use of preassembled brickwork supported on reinforced concrete or steel frames offers the builder a potentially higher level of quality control and increased speed of construction on site Fig.

It also offers the scope to create complex details and forms, such as long low arches, that would be expensive or impossible in traditional brick construction. Specialist manufacturers produce large complete brick-clad precast concrete panels with either whole bricks or brick slips. Photograph: Courtesy of Trent Concrete Ltd.

The brick slips are laid out with spacers within the panel mould, prior to the addition of steel reinforcement and concrete. Finally the brick slips are pointed up giving the appearance of normal brickwork. Factory-made brickwork panels of solid wall dimensions and single-storey height, incorporating openings and ducts for windows, doors and electrical installations, enable fast erection on site for domestic-scale construction.

One manufacturer supplies bay window units constructed on steel frames for easy installation on site. In one system, external walls are constructed with mm aerated concrete blockwork and faced with an extruded polystyrene insulation panel to which 16 mm brick slips are applied onto the pre-formed grid, giving the appearance of standard external leaf brickwork.

The polystyrene grid panels have an overlap to ensure horizontal joints are watertight and are tongued and grooved to interlock vertically. Adhesive is applied to the polystyrene and the brick slips are pushed into place with the appropriate horizontal spacing. With the use of highly insulating blocks, this type of construction can achieve U-values as low as 0. The specially shaped brick tiles then clip into the steel system with appropriate vertical joint spacing.

A range of special tiles is manufactured to produce dados, plinths, cills and external returns, giving the appearance of traditional brickwork. Because the brickwork is non-structural, a range of bond patterns including stack, quarter and diagonal is optional. The material offers a human scale to large areas of hard landscape, especially if creative use is made of pattern and colour. Typical patterns Fig. However, it should be noted that not all paver sizes co-ordinate for herringbone and basket-weave designs.

Edge restraint is necessary to prevent lateral spread of the units. Slip resistance for the unpolished pavers is categorised Table 1. Photographs: Courtesy of Baggeridge Brick Plc. Research into mix design and the development of improved manufacturing processes subsequently led to the production of a full range of load-bearing-strength classes and attractive facings. Actual tolerances are usually less than one millimetre.

Modular and bricks of Imperial thickness can be made to order. If quicklime is used, it is fully hydrated before the bricks are pressed, to prevent expansion under the steam treatment.

A mixture of sand, lime and water is used to manufacture the natural white sandlime brick. Subsequently the calcium silicates react slowly with carbon dioxide from the atmosphere to produce calcium carbonate, with a gradual increase in the strength of the bricks.

The colour range is extensive, from white and pastel shades through to deep reds, blues, browns, greens and yellows. The visual effect on the brickwork tends to be that of precision. The bricks tend to be more brittle than clay bricks and are therefore more susceptible to damage on their arrises. The bricks are themselves resistant to sulphate attack and can therefore be used below ground with a suitable sulphate-resisting cement mortar.

However, calcium silicate bricks should not be used as pavers where winter salting can be expected. The thermal conductivity of calcium silicate brick ranges from 0.

Weight Most standard calcium silicate bricks weigh between 2. Acoustic properties Acoustic properties are related to mass and are therefore the same as for clay bricks of equivalent density. This shrinkage is increased if the bricks become wet before use; therefore, site protection of brick stacks from saturation is essential.

Reversible moisture movement is greater for calcium silicate bricks than for clay bricks, so expansion joints must be provided at intervals between 7.

Such movement joints should not be bridged by rigid materials. Generally a weak mortar mix should be used e. The use of complementary coloured mortars enhances the aesthetic effect when using strongly coloured bricks. Their dimensional accuracy gives some advantage in the bricklaying process, and cost is comparable to that of the equivalent clay bricks. Incorporated within the ivory Flemish-bond brickwork are restrained bands of polychromatic features and robust articulation of obtuse-angle quoins.

Due to their manufacturing process, concrete bricks can be made to close tolerances, so accurate alignment is easy to achieve on site. Half-brick walls can readily be built fairfaced on both sides. The use of coloured aggregates also increases the colour range. The accurate manufacturing process produces bricks that have clean arrises. Surfaces range from smooth to simulated natural stone, including those characteristic of handmade and textured clay bricks.

Because of the wide range of pigments used in the manufacturing process, it is possible to match effectively new concrete bricks to old and weathered clay bricks for the refurbishment or extension of old buildings. Compressive strengths and densities are manufactured to client requirements. A normal range of specials to BS is produced, although as with clay and calcium silicate bricks, a longer delivery time must be anticipated. Like all concrete products, they harden and increase in strength with age.

Acoustic properties Dense concrete bricks are suitable for the reduction of airborne sound transmission. On a weight basis, they are equivalent to clay and calcium silicate bricks. Moisture and thermal movements are greater than those for calcium silicate bricks and movement joints should be at 5—6 m centres. Because of their moisture movement, prior to laying, concrete bricks should not be wetted to overcome excessive suction, but the water retentivity of the mortar should be adjusted accordingly.

Brick stacks should be protected on site from rain, frost and snow. The visual effects of using coloured mortars and various jointing details are as for clay bricks, but for exposed situations the use of raked joints is not recommended. Thermal conductivity The thermal conductivities of concrete bricks are equivalent to those of clay and calcium silicate bricks of similar densities.

The thermal conductivity of concrete bricks ranges between 1. An appropriate level of thermal insulation for external walls can be achieved using concrete brickwork. The visual effect is that of standard brickwork without the mortar joints.

The system is suitable for cladding steel or timber frame buildings up to 18 m in height. It may also be used on conventional masonry or insulated concrete formwork ICF construction. The system has resistance to moisture penetration but is not airtight. A range of colours from buff, beige and brown through to red is available. The horizontal joints are slightly chamfered to give an impression of standard brickwork coursing.

Properties of bricks and mortar generally, No. Windsor: BDA. Brick Development Association. London: Butterworth Heinemann. British Cement Association. Camberley: British Cement Association. Campbell, J. London: Thames and Hudson. Hammett, M. Windsor: Brick Development Association. Marlborough: Crowood.

Hendry, A. London: E. Institution of Structural Engineers. London: ISE. Knight, T. London: Arnold. Kreh, D. Nantwich: Delmar. McKenzie, W. London: Palgrave. Mortar Industry Association. Data Sheet 8. London: Mortar Industry Association. Sovinski, R. Bognor Regis: John Wiley and Sons. Weston, R. London: Laurence King Publishing. BS Clay and calcium silicate bricks of special shapes and sizes. BS Code of practice for use of masonry: Part 1: Structural use of unreinforced masonry.

Part 3: Materials and components, design and workmanship. BS Precast concrete masonry units: Part 2: Guide for specifying precast concrete masonry units. BS Building and civil engineering vocabulary: Part 0: Introduction. Part 6: Construction parts. BS Pavements constructed of clay, natural stone or concrete pavers. BS Workmanship on building sites: Part 3: Code of practice for masonry.

BS Structural design of low rise buildings: Part 2: Code of practice for masonry walls for housing. BS Code of practice for design and installation of damp-proof courses in masonry construction. Part 2: Calcium silicate masonry units. Part 3: Aggregate concrete masonry units.

Part 4: Autoclaved aerated concrete masonry units. Part 2: Lintels. Part 3: Bed-joint reinforcement of steel meshwork. BS EN Admixtures for masonry mortar.

Masonry mortar. BS EN Methods of test for mortar for masonry. BS EN Methods of test of masonry. BS EN Clay pavers. Requirements and test methods. Part 1. Part 2: Design considerations, selection of materials and execution of masonry. Design considerations, selection of materials and execution of masonry.

BS EN Aggregates for mortar. PAS HD clay bricks. Guide to appearance and site measured dimensions and tolerance. DD Wall ties. Recommendations for design of wall ties. BRE Digest Corrosion of metal components in walls. Masonry Part 3. BRE Digest Principles of masonry conservation management.

U-values and building regulations. A decade of development. Measurement procedure. Hammett and R. DN Improved standards of insulation in cavity walls with outer leaf of facing brickwork. Ford and W. DN The design of curved brickwork. Hammett and J. DN The use of bricks of special shape. DN Brick cladding to timber frame construction. Building note BN 1: Brickwork. Good site practice. Technical information paper TIP Brickwork dimension tables.

Technical paper Lilley, A. Where visual blockwork is required, either internally or externally, fairfaced blocks offer a selection of textures and colours at a different visual scale compared to that associated with traditional brickwork.

Externally, visual concrete blockwork weathers well, provided adequate attention is given to the quality of the material and rainwater run-off detailing. Blockwork has considerable economic advantages over brickwork in respect of speed of construction, particularly as the lightweight blocks can be lifted in one hand.

Whilst clay blocks are used extensively for masonry construction on the continent of Europe, until recently there had been little demand from the building industry within the UK. Gypsum blocks may be used for internal non-load-bearing partitions and the internal insulation of walls.

Concrete paving blocks, which offer opportunities for creative hard landscaping with their diversity of form and colour, are widely used for town pedestrian precincts and individual house driveways. Concrete interlocking blocks with planting are used to create environmental walls.

Concrete blocks are manufactured to various work face dimensions in an extensive range of widths, offering a wide choice of load-bearing capacity and level of insulation. Manufacturers work size dimensions should be indicated as length, width and height, in that order, to BS EN and BS The use of thinjoint masonry offers speedier construction, especially when using large format blocks Fig. However, blocks heavier than 20 kg should not be lifted by a single person as this potentially can lead to injury.

Under the European Standard, the minimum Fig. Widths quoted by certain manufacturers include: 50, 70, 75, , , , , , , , , , , , , and mm. Common crushing strengths to BS are 2. Table 2. Therefore, most units used within the UK conform to tolerance categories D1 and D2. Closer tolerances may be declared by the manufacturer.

Medium and lightweight concrete blocks are manufactured incorporating a wide range of aggregates including expanded clay, expanded blastfurnace slag, sintered ash and pumice. Concrete is cast into moulds, vibrated and cured. The hydrogen gas generated by the dissolution of the metal powder produces a non-interconnecting cellular structure. The process is accelerated by pressure steam curing in an autoclave Fig.

Standard blocks, typically natural grey or buff in colour, are usually shrinkwrapped for delivery. However, the majority of concrete blocks fall in the range from 2. Drying shrinkages are typically in the range 0. However, some lightweight concrete blocks, with less than 7 MPa crushing strength should not be used below DPC level, except for the inner skin of cavity construction.

Individual U-values for elements are therefore not set, except for extensions on existing dwellings Part L1B and other existing buildings Part L2B where an indicative Uvalue of 0. The limiting area-weighted U-value standard for wall elements in new buildings is 0. The following material combinations achieve a U-value of 0. Similarly, a U-value of 0. The thin-joint mortar system for inner leaf blockwork gives slightly enhanced U-values compared to the equivalent standard 10 mm joint blockwork construction.

Rendered solid wall construction can also achieve a U-value of 0. Phase change material blocks Phase change materials PCMs incorporated into aerated concrete blocks offer some additional thermal stability to the internal environment by absorbing excessive summer heat, which is then released during the cooler periods.

The phase change material is described in Chapter 12 page For domestic construction the appropriate Robust Details should be used to ensure compliance with thermal and sound requirements of the Building Regulations. Sound insulation The Building Regulations Approved Document E recognises the need to provide adequate sound insulation both between and within dwellings also between rooms in hostels, hotels and residential accommodation.

The regulations require minimum airborne sound insulation of 45Rw dB for separating walls and 40Rw dB for internal bedroom or WC walls. The passage of airborne sound depends on the density and porosity of the material. The following alternative systems should perform to the required airborne insulation standard for separating walls of new build dwellings.

Vertical chases should, in any case, not be deeper than one third of the block thickness. Horizontal chases should be restricted to not more than one sixth of the block thickness, due to the potential loss of structural strength.

Acoustic absorbing concrete blocks are manufactured with a slot on the exposed face which admits sound into the central cavity Fig. Acoustic control blocks in fairfaced concrete are suitable for use in swimming pools, sports halls, industrial buildings and auditoria.

The use of specials in fairfaced blockwork can greatly enhance visual qualities. Matching full-length lintels may incorporate dummy joints and should bear on to full, not cut, blocks. Frequently the colour is all through, although some blocks have an applied surface colour. Textures range from polished, smooth and weathered sand- or shot-blasted to striated and split face Fig. The glazed blocks are available in an extensive range of durable bright colours and are suitable for interior or exterior use.

Most manufacturers produce a range of specials to co-ordinate with their standard fairfaced blocks, although, as with special bricks, they may be manufactured from a different batch of mix, and this may give rise to slight variations. Photographs: Courtesy of Lignacite Ltd.

For internal walls, blocks are mm long and range in widths from to and mm. Horizontal joints require 10 mm of a lightweight mortar, but the vertical joint edges, if tongued and grooved, remain dry. The LD units may be vertically or horizontally perforated, with butt jointing, mortar pockets or a tongue and groove system Fig.

Special blocks are available for corners, lintels, door and window openings, but individual blocks can also be cut. A standard 10 mm mor- tar joint is appropriate, which may match or contrast with the block colour.

The maximum thickness to BS EN is mm. The preferred face dimensions are mm in length and mm in height, with a maximum length of mm. Gypsum blocks may be used as non-load-bearing partitions and internal insulation of walls. Whilst blocks can be cut with a masonry cutter, the addition of small pieces of block, or the widening of perpends over the 10 mm standard, is unacceptable. Curved blockwork may be constructed from standard blocks, the permissible curvature being dependent on the block size.

The oversail between alternate courses should not normally exceed 4 mm in fairfaced work. If the internal radius is exposed, then the perpends can be maintained at 10 mm with uncut blocks, but if the external radius is exposed, the blocks will require cutting on a splay. For tighter curves specials will be required. Heavier blocks require mechanical lifting or two-person handling. The mortar is applied manually with a serrated scoop of the appropriate width or through a pumped system to achieve uniformity.

Architect: IDP. The special rapid-setting mortar sets typically within 60 minutes and the full bond strength is achieved after only 2 hours, allowing more courses to be laid each day. Bed joints in thin-layer mortar blockwork do not necessarily co-ordinate with those of the brickwork, so conventional cavity wall ties can only be used if they are slope-tolerant.

The acoustic properties of thin-joint mortar walls differ slightly from those of walls constructed with 10 mm mortar joints. Resistance to low-frequency noise is slightly enhanced, whilst resistance to highfrequency sound is slightly reduced. Completed thin-joint blockwork acts as a monolithic slab, which, if unrestrained, may crack at the weaker points, such as near openings.

To avoid this, the block units should be laid dry to avoid shrinkage and bed joint reinforcement 1. Larger structures require movement joints at 6 m centres. Certain extruded multi-perforated clay and calcium silicate blocks are designed for use with thin mortar bed joints and dry interlocking vertical joints.

Whilst this reduces the initial construction time, exposed sides of the units subsequently require plaster or cement render to minimise heat loss by air leakage. Bed-joint reinforcement would be inserted into two bed joints above and below such openings Fig.

Cover to bed reinforcement should be at least 25 mm on the external faces and 13 mm on the internal faces. Combined vertical and horizontal reinforcement may be incorporated into hollow blockwork in accordance with BS , where demanded by the calculated stresses.

Blockwork may incorporate banding of concrete bricks, but because of differences in thermal and moisture movement, it is inadvisable to mix clay bricks with concrete blocks. Such panels will require reinforcement Concrete blockwork is subject to greater movements than equivalent brickwork masonry. Therefore, the location and form of the movement joints requires greater design-detail consideration, to ensure that inevitable movements are directed to the required locations and do not cause unsightly stepped cracking or fracture of individual blocks.

Ideally, such movement joints should be located at intersecting walls, or other points of structural discontinuity, such as columns.

Additionally, movement joints are required at changes in thickness, height or loading of walls, above and below wall openings, and adjacent to movement joints in the adjoining structure Fig. External unreinforced non-load-bearing concrete masonry walls with a length to height ratio of 3 : 1 or less must be separated into a series of panels with vertical movement-control joints at approximately 9 m centres or more frequently for masonry walls with a length to height ratio of more than 3 : 1 NA to BS EN Wall ties should allow for differential movement between the leaves in cavity construction and should be spaced at mm horizontally and mm vertically, for 50—75 mm cavities.

Bucket handle and weathered or struck joints are suitable for external use, but recessed joints should only be used internally. Coloured mortars should be ready mixed or carefully gauged to prevent colour variations. Where blockwork is to be rendered, the mortar should be raked back to a depth of 10 mm for additional key. Interlocking foundation blocks, with a tongue and groove vertical joint, slot together with only bed-joint mortar being required.

A handhold makes manipulating these blocks on site much easier than lifting standard rectangular blocks. Thicknesses within the range — mm are standard. Blocks intended for plastering have a textured surface to give a good key.

Fairfaced blockwork may be left plain or painted. Where standard blocks are to be painted, the appropriate grade should be used. Beams may be inverted T or I in form, alternatively incorporate partially exposed lattice girder reinforcement to be covered within a concrete topping.

Insulation will be required to achieve a U-value between 0. The render should terminate at damp-proof course level with a drip or similar weathering detail. Portland cement blocks Fig. Photographs: Courtesy of Marshalls Plc. The following material combination achieves a U-value of 0.

Alternative designs include tumbled blocks, which emulate granite setts, and various interlocking forms giving designs based on polygonal and curvilinear forms. For most designs, a range of kerb blocks, drainage channels, edging and other accessory units are available. Concrete paving blocks are usually laid on a compacted sub-base with 50 mm of sharp sand.

For the wider joints that occur between the simulated stone setts a coarser grit can be used to prevent loss by wind erosion. Guidance on the design and construction of pavements for a range of applications is given in BS Parts 1—13 inclusive. Sustainable urban drainage systems SUDS are designed to reduce the environmental impact of impermeable hard landscaping surfaces which create rapid rainwater run-off. With permeable surfaces, including nibbed blocks, the rainwater permeates through the spacing and is dispersed by natural drainage into the underlying soil, or may be collected through rainwater harvesting systems for further use.

Sulphate-resisting blocks are available if dictated by the soil conditions. Soil is placed in the pockets of each successive course to allow for planting. The size of the block determines the maximum construction height, but over 20 m can be achieved with very deep units. Limited wall curvature is possible without cutting the standard blocks. The systems are used both for earth retention and to form acoustic barriers. Camberley: BCA. Concrete Block Association.

Part L. Thermal insulation from April Guidance for designers and users. Leicester: CBA. Aggregate block sustainability. Data Sheet Concrete Society. Technical Report No. Camberley: The Concrete Society. Hugues, T. Details, products, built examples. Robust Details. Milton Keynes: Robust Details Ltd. Part 2: Structural use of reinforced and prestressed masonry. BS Glossary of building and civil engineering terms: Part 0: Introduction.

Part 1: General terms. Part 6: Code of practice for laying natural stone, precast concrete and clay kerb units. BS Structural design of low-rise buildings: Part 2: Code of practice for masonry walls for housing. BS EN Masonry cement. Part 5: Manufactured stone masonry units.

Part 3: Bed joint reinforcement of steel meshwork. Part 2: Concrete admixtures. BS EN Concrete paving blocks. BS EN Masonry and masonry products. Methods for determining design thermal values. BS EN Chimneys. BS EN Gypsum blocks. BS EN Gypsum based adhesives for gypsum blocks. Linear thermal transmittance. Plastic and rubber damp proof courses. BS EN Precast concrete products. Part 2: Concrete blocks. Part 3: Clay blocks.

Nonloadbearing walls: Part 2: Masonry and gypsum blocks. BS EN Design and application of gypsum blocks. Normal weight and lightweight concrete shuttering blocks. Product properties and performance. Part 4. Materials behaviour: Masonry. Part 2. Structural performance when using AAC blockwork.

However, in this context, its use is restricted to that of a binding agent for sand, stone and other aggregates within the manufacture of mortar and concrete. Hydraulic cements and limes set and harden by internal chemical reactions when mixed with water. Non-hydraulic materials will harden slowly by absorption of carbon dioxide from the air.

Lime was used as a binding agent for brick and stone by the ancient civilisations throughout the world. Outside Britain, the Romans frequently mixed lime with volcanic ashes, such as pozzolana from Pozzuoli in Italy, to convert non-hydraulic lime into a hydraulic cement suitable for use in constructing aqueducts, baths and other buildings.

In the eighteenth century, so-called Roman cement was manufactured by burning the cement stone argillaceous or clayey limestone , collected from the coast around Sheppey and Essex.

In , Joseph Aspdin was granted his famous patent for the manufacture of Portland cement from limestone and clay. Limestone powder and clay were mixed into a water slurry which was then evaporated by heat in slip pans.

The name Portland was used to enhance the prestige of the new concrete material by relating it to Portland stone which, in some degree, it resembled. Early manufacture of Portland cement was by intermittent processes within bottle, and later chamber, kilns.

The introduction of the rotating furnace in offered a continuous burning process with consequent reductions in fuel and labour costs. The early rotating kilns formed the basis for the development of the various production systems that exist now.

Year was the peak of production when 18 million tonnes of cement was manufactured within the UK. About half of this was required by the readymixed concrete industry; the remainder was divided roughly equally between concrete-product factories and bagged cement for general use. The mineral is quarried, crushed, ground, washed and screened to the required size range. Subsequent treatments produce the product range given in Fig. Generally, the addition of lime to cement mortar, render or plaster increases its water-retention properties, thus retaining workability, particularly when the material is applied to absorbent substrates such as porous brick.

Lime also increases the cohesion of mortar mixes allowing them to spread more easily. Hydrated lime absorbs moisture and carbon dioxide from the air, and should therefore be stored in a cool, draught-free building and used whilst still fresh. Alternatively, it can be made by stirring hydrated lime into water, followed by conditioning for at least 24 hours.

Lime putty may be blended with Portland cement in mortars where its water-retention properties are greater than that afforded by hydrated lime. Additionally, lime putty, often mixed with sand to form coarse stuff, is used directly as a pure lime mortar, particularly in restoration and conservation work.

It sets, not by reaction with sand and water, but only by carbonation, and is therefore described as non-hydraulic. Carbonation Lime hardens by the absorption of carbon dioxide from the air, which gradually reconverts calcium oxide back to calcium carbonate. The controlled addition of water to quicklime produces hydrated lime S mainly calcium hydroxide as a dry powder. The maximum size of aggregate mixed into lime mortars should not exceed half the mortar-joint width. The materials produced have some of the properties of Portland cement, and partially harden through hydration processes, rather than solely through carbonation, as happens with non-hydraulic pure calcium oxide lime.

Hydraulic limes rich in clay impurities are more hydraulic and set more rapidly than those with only a low silica and alumina content. These traditional grades equate approximately to the 28 day compressive strengths of 2, 3. Eminently hydraulic lime mortar is used for masonry in exposed situations, moderately hydraulic lime mortar is used for most normal masonry applications and feebly hydraulic lime mortar is appropriate for conservation work and solid wall construction.

Materials for Architects and Builders is written as an introductory text to inform students at undergraduate degree and national diploma level of the relevant visual and physical properties of the widest range of building materials.

The fourth edition has been significantly enhanced by the addition of more colour images, illustrating the materials and, in many cases, their use in buildings of architectural merit. The text embraces the broad environmental issueswith sections on energy saving and recycled materials. An additional chapter on sustainability reflects the current debate on climate change and governmental action to reduce carbon emissions and ameliorate global warming. There are eighteen chapters covering the wide range of materials under standard headings.

Each chapter describes the manufacture, salient properties and typical uses of the various materials, with the aim of ensuring their appropriate application within awareness of their ecological impact. European Standards are taking over from the previous British Standards, and for most key materials, the European Norms have now been published. Generally, this has led to an increase in the number of relevant standards for building materials.

However, in some cases, both the British and European Standards are current and are therefore included in the text and references. New and rediscovered old materials, where they are becoming well integrated into standard building processes, are described, together with innovative products yet to receive general acceptance. Other materials no longer in use are generally disregarded, except where increased concern for environmental issues has created renewed interest.