Carousel Next. What is Scribd? Explore Ebooks. Bestsellers Editors' Picks All Ebooks. Explore Audiobooks. Bestsellers Editors' Picks All audiobooks. Explore Magazines. Editors' Picks All magazines. Explore Podcasts All podcasts. Difficulty Beginner Intermediate Advanced. Explore Documents. BS 1. Uploaded by Winston Cky. Did you find this document useful? Is this content inappropriate? Report this Document.
BS , Specification for window sills of precast concrete, cast stone, clayware, slate and natural stone. BS , Specification for copings of precast concrete, cast stone, clayware, slate and natural stone. BS , Lintels. Method of assessment of load. BS , Code of practice for painting of buildings. BS , Selection of construction sealants Guide. BS , Specification for bitumen damp-proof courses for masonry. BS various parts , Ceramic floor and wall tiles.
BS , Installation of chimneys and flues for domestic appliances burning solid fuel including wood and peat Code of practice for masonry chimneys and flue pipes BS , Specification for steel windows, sills, window boards and doors. BS , Specification for polyethylene damp-proof courses for masonry.
BS , Specification for ground granulated blast furnace slag for use with Portland cement. BS , Specification for mastic asphalt for building and civil engineering limestone aggregate.
BS , Code of practice for stabilization and thermal insulation of cavity walls with masonry or concrete inner and outer leaves by filling with polyurethane PUR foam systems. BS , Specification for polyurethane PUR foam systems suitable for stabilization and thermal insulation of cavity walls with masonry or concrete inner and outer leaves.
BS , Specification for limestone fines for use with Portland cement. BS , Part 3: Code of practice for masonry. BS , Code of practice for foundations. BS , Code of practice for protection of structures against water from the ground. BS various parts , Structural design of low-rise buildings.
BS , Code of practice for assessing exposure of walls to wind-driven rain. BS , Code of practice for design and installation of damp-proof courses in masonry construction. BS EN , Technical conditions for inspection and delivery. BS EN , Mechanical properties. BS EN , Chemical composition. BS EN , Forms of products. BS EN , Specification for masonry units. BS EN , Clay masonry units. BS EN , Calcium silicate masonry units.
BS EN , Aggregate concrete masonry units dense and light-weight aggregates. BS EN , Autoclaved aerated concrete masonry units. BS EN , Manufactured stone masonry units. BS EN , Natural stone masonry units. BS EN , Specification for ancillary components for masonry. BS EN , Ties, tension straps, hangers and brackets. BS EN , Lintels. BS EN , Bed joint reinforcement of steel meshwork. BS EN , Admixtures for concrete, mortar and grout Admixtures for masonry mortar Definitions, requirements and conformity.
BS EN , Mixing water for concrete Specification for sampling, testing and assessing the suitability of water as mixing water for concrete. BS EN , Methods of test for mortar for masonry Determination of flexural and compressive strength of hardened mortar. Sealants Classification and requirements. BS EN , Aggregates for concrete.
BS EN , Lightweight aggregates for concrete, mortar and grout. BS EN , Aggregates for mortar. NOTE 2 Cladding may be continuous or in panels. Guidance on regulatory requirements and design options to avoid heavy units can be found in manufacturers literature or in [1]. Clay flue blocks should conform to BS EN NOTE Primary classification of building stones is ordered into the three major groups:. The use of high alumina cement is not permitted.
Aggregates from natural sources to be used for concrete should conform to BS EN For guidance on their use see 5. In practice, mains water or other potable supplies are satisfactory. However, in cases where water supplies are of doubtful quality, the methods of water sampling and testing should conform to BS EN For guidance on selection and use of wall ties see 5. Joist hangers required for both vertical and lateral support as shown in BS , Annex D should be purpose made.
Support should conform to BS EN Materials for other types of support and restraint components such as support angles, dowels and fixings should conform to one or other of the specifications listed in BS EN , 2 or 3. For guidance on the selection of materials see 5. NOTE 1 A variety of metal components is available to tie and provide restraint for masonry cladding.
NOTE 2 A variety of metal components is available to support masonry cladding panels and corbelled forms of masonry. Typical applications are illustrated in Figure 16 and Figure Reinforcement for non-structural use, e. Bed joint reinforcement of steel meshwork should conform to BS EN The suitability criteria for materials for d. Sealant selection should be in accordance with the recommendations given in BS Sealants should be installed in accordance with BS NOTE Guidance on the application of sealants and on back-up materials in sealed joints is given in 5.
For the selection of a sealant for use with a particular type of natural stone, the sealant manufacturer should be consulted to avoid problems such as migration staining. Some silicone sealants liberate acidic by-products during curing and are therefore unsuitable for use with calcareous stones. Flues should follow the recommendations given in BS or BS , as appropriate. Unless satisfactory local experience exists, clay products should not be used in limestone masonry nor concrete products used in sandstone masonry.
These restrictions avoid the risk of attack by run-off from limestone and concrete, respectively. Sill materials should conform to the British Standards given in Table 3. NOTE For guidance on d. Concrete and masonry lintels should be selected to have adequate concrete quality and cover to protect the reinforcement in their conditions of exposure. Autoclaved aerated concrete Cast concrete Reinforced concrete Prestressed concrete Pressed steel Rolled low carbon steel.
NOTE 1 For guidance on the design of, and the need for, d. NOTE 2 Table 13 provides information regarding the durability of masonry in finished construction. NOTE For guidance on the use of flashings and weatherings, see 5. NOTE Insulation products may be installed in the cavity of a cavity wall partially or fully to fill it see 5.
Insulation products are produced in different forms to suit the various installation methods used seeTable 8 and A. A For installation during construction of masonry to fill the cavity partially Mineral wool slabs glass or rock fibre. B For installation during construction of masonry to fill the cavity fully Mineral wool insulation slabs glass or rock fibre BS EN C For installation by blowing or injection into cavity walling to fill the cavity fully Loose mineral wool glass or rock fibre. For: choice of masonry unit materials, see 4.
Consideration should be given to the interaction of the whole structure, of which the masonry forms a part.
Connections of other elements with the walls should be sufficient so as to transmit all vertical and lateral loads safely to the foundations. If necessary during construction, temporary support for masonry should be used, e. The structural design of masonry should be in accordance with the recommendations of BS and -2, and for low-rise buildings should be in accordance with the recommendations of BS The effect of introducing openings, movement joints or slip planes should be carefully considered.
The need for robust construction, including the effect of accidental loading, should always be taken into account in the design. Where necessary, suitable bearing plates, spreader beams, padstones, piers or columns should be provided for lintels or beam bearings see 5. Certain types of cellular, frogged or hollow unit which are otherwise suitable for the construction of the wall may not provide sufficient bearing strength at points of concentrated load and may need to be filled.
NOTE Empirical guidance on maximum height and minimum foundation width of brick or block masonry free-standing walls is given in [2]. Similar guidance on reinforced, diaphragm and wide plan e. However, certain rectangular walls and gables in buildings up to and including four storeys high may be proportioned as in Table 8, subject to the following conditions.
Three- or four-sided support should be assumed as appropriate. A fixed support may be assumed in a single-leaf, collar joint or grouted-cavity wall in the cases shown in Figure 3a and Figure 4 or where the wall abuts, and is adequately tied to, a column capable of resisting horizontal forces applied to it without excessive deflection.
Dimensions in millimetres. Figure 4 Fixed support assumed in a single-leaf, collar joint or grouted-cavity wall A fixed support may be assumed in a cavity wall in the cases shown in Figure 5. A simple support may be assumed where the wall is permitted to rotate but is restrained against lateral movement. The design should contain provisions for any chases cut in the wall see 5. The length or height of the wall in relation to its thickness should be within the limits given in Figure 6.
The following factors, which affect stability, should be provided for in the design: a accommodation for movement see 5. When an internal wall or partition is to be plastered, a thickness of not more than 13 mm of plaster to one or both sides of the partition should be included when determining the thickness of the wall for design in accordance with Figure 6.
Dry lining should not be considered as contributing to the thickness of the wall. NOTE 1 Until the wall has been plastered it will not have its final strength. NOTE 2 Figure 6 is derived from the following empirical formulae. Figure 6 Limiting dimensions of walls for stability 5. Where the design relies on flexural strength and no guidance is given in BS on the adhesion characteristics of the particular masonry units and mortar strength class, the adhesion should pass the preliminary tests described in BS , A.
In the particular case of low-rise buildings, reference should be made to BS In Figure 7, the encircled numbers labelling a feature refer to the figure showing the feature in more detail. Where more than one type of restraint system is given at an element intersection, only one of the options should be used.
Figure 7 Location and types of connection necessary between elements of a typical building 5. Where floors are required to provide lateral restraint, the recommendations of BS , Annex D, or BS should be followed. Where practicable, suspended timber floors near to the ground should be supported independently of the main structure by sleeper walls.
Where this is not practicable, offsets or corbels from external walls may be used. Suspended timber floors at other levels should be built into the walls or supported by offsets, corbels or joist hangers. Timber wall plates should not be built into any wall. Unreinforced concrete floors laid on the ground, or on fill, should not also bear on walls as this can give rise to cracking as a result of differential movement. The bearing of all types of floor and support fittings should be not less than 75 mm.
Concrete floors should have a bearing of not less than 90 mm, however, this bearing may be reduced at the discretion of the designer provided relevant factors such as loading, span, tolerances, height of support and the provision of continuity reinforcement should be taken into account.
NOTE The tension strap should be carried over at least three joists and be secured with four fixings of which at least one should be in the third joist, or in a nogging beyond the third joint. Otherwise, strap as shown; on top of the joist with the strap turned up or on one side of joist with strap turned sideways alternative positions are shown in BS , Figure D. Figure 9 Alternative methods of supporting floor joists and providing restraint concluded.
Figure 10 Alternative methods of connecting concrete slab floors 5. Typical ways of connecting roofs with walls are shown in Figure 11, Figure 12 and Figure The bearing on walls of timber joists and joist hangers should be not less than 75 mm.
Frogs of bricks should be filled to provide an even bearing. It may be desirable to provide a wall plate in certain cases. Concrete roofs should have a bearing of not less than 90 mm; however, this bearing may be reduced at the discretion of the designer provided that relevant factors such as loading, span, tolerances, height of support and the provision of continuity reinforcement are taken into account. NOTE 1 Binders or other beams giving rise to concentrated loads on the wall may need to be provided with a padstone or spreader beam see 5.
NOTE 2 When detailing the bearings of flat roofs upon walls, the danger of displacement of the top courses of masonry as a result of thermal movements in the roof and deflection of the structure should be taken into account. Temperature variations can be reduced by providing external insulation or reflective coatings to the roof.
NOTE 2 The soffit board should be securely fixed to the ladder bracket and should also be a close fit to the wall. Figure 13 Restraining roofs against displacement 5.
Where lintels are used, these should have bearings commensurate with the solidity of the support see 5. Lintels should not bear on a short length of cut block. Where possible, the masonry should be set out to provide a full length, whole depth unit under a bearing. The assessment of load on lintels may be in accordance with BS Pressed steel lintels should have a bearing of not less than mm in length and may need stiffening over the bearing length to resist the total load.
Protective measures for steel lintels, including provision of d. Where composite lintels, e. Installation should follow the recommendations of the manufacturers. The design compressive and tensile resistance of the wall ties relevant to the nominal cavity width should exceed the design lateral loads to which they will be subjected.
The choice of the type of wall tie and spacing depends on the cavity width and the lateral load to be transmitted between the two leaves BS , Table 1 gives recommendations for the selection of wall ties with regard to material specifications and situation. Ties are available with suitable retaining devices for retaining insulation products against one masonry face. Wall ties are also available for masonry cladding of timber, steel or concrete frame constructions. Wall ties should be evenly distributed over the wall area, except around openings, and preferably should be staggered.
At the vertical edges of openings and at vertical unreturned or unbonded edges e. Unless specified otherwise for structural reasons, the length of the tie should be sufficient to give a depth of embedment of at least Suitable minimum lengths for ties are given in Table 9. Where wall ties with an embedment length other than 50 mm are required, site practice should be such as to ensure that the embedment length is achieved.
Table 9 Selection and spacing of wall ties A Spacing of wall ties Least leaf thickness one or both. B Selection of wall ties: types and lengths Permissible type of wall tie Least leaf thickness one or both. Types 1, 2, 3 or 4 selected on the basis of the design loading and design cavity width. Where face insulated blocks are used the cavity width should be measured from the face of the concrete. This column gives the tie lengths, in 25 mm increments, that best meet the performance requirement that the embedment length will be not less than 50 mm in both leaves after taking into account all building and materials tolerances but that the ties should also not protrude from the face.
For cavities wider than mm calculate the length as the structural cavity width plus mm and select the nearest stock length. The designer may vary the length in particular circumstances, provided that the design requirements continue to be met.
Corbelled feature work may be built with restraint fixings subject to structural engineering design. Figure 14 Extent of corbelling 5. See 5. The design should contain provision for the effects of chasing on stability, particularly where walls or leaves are constructed of hollow units, and the recommendations set out in BS considered. In walls or leaves constructed of solid units, the depth of horizontal chases should be no greater than one-sixth of the thickness of the single-leaf at any point, and the depth of vertical chases should be no greater than one-third of the thickness of the single-leaf at any point.
The cutting of holes up to approximately mm2 square i. The design should contain provision regarding the effect on the stability of the masonry where heavy fittings are to be fixed to a wall. After construction, buildings are subject to small dimensional changes, which can be caused by one or more of the following factors: a change in temperature see B. It should not be confused with absorption, which refers to the entry of water molecules into the pores of the masonry.
To guard against dimensional changes occurring as a result of sulfate attack, the recommendations set out in 5. Masonry is not completely free to expand or contract because restraints are often present, and thus compressive or tensile forces can develop and these can lead to bowing or cracking. Where the compressive forces are applied eccentrically, e. Where there are stress concentrations, for example, at openings or at changes in height, thickness or direction of walls, and where stronger mortars than those recommended in 5.
All materials expand and contract in response to thermal changes. In addition, clay materials undergo an irreversible expansion after their manufacture as moisture is adsorbed from the atmosphere. Other masonry materials shrink following manufacture to reach the equilibrium state. Units made from different types of material should not be bonded together in masonry in a manner that would cause stress to develop as a result of dissimilar characteristic movement, e.
Where anticipated movements are different in magnitude and nature, parts of masonry of different material type should be effectively separated, e. Alternatively, they should be suitably reinforced see Annex B and 5. The causes of cracking in buildings, including movements, and guidance for a broader understanding of the factors and mechanisms involved are reviewed in [4]. However, for brick masonry of certain clay bricks in applications where restraint is low e. In such cases the manufacturer should be consulted.
Joints should be built-in as work proceeds. When designing movement joints in separating walls, party walls or compartment walls, the reduction in the efficiency of the wall as an insulator of sound, or as a fire barrier see 5.
Where necessary, slip ties or dowels strong enough to provide lateral stability should be incorporated. They are usually of metal rod or flat strip and one end is anchored, or otherwise fixed, into masonry on one side of a movement joint. The other end is built-in but debonded to allow the joint to open and close while preventing movement in any other direction.
The design and positioning of movement joints and slip planes should be carefully considered, to ensure that in addition to accommodating movements, such joints or planes do not impair the stability of the wall or any of its functions. In external wails, movement joints and slip planes should be sealed, protected or otherwise designed to prevent water penetration see 5.
Fixings and services should not interfere with the performance of the joints or slip planes, e. Finishes should be discontinuous at movement joints and slip planes, and fixings and fittings should not tie across joints. It is not necessary to provide movement joints where the length of internal walls or the inner leaves of cavity walls in dwellings is relatively short. The spacing of the first movement joint from an external or internal angle should be not more than half the general spacing, and preferably less, where the masonry is continuous at the angle, due to the effect of end restraint of the wall panel.
When more detailed information is needed on basic data and design to accommodate movement, see Annex B. The material manufacturers should also be consulted. The spacing and width of movement joints to control expansion in such walls is governed by the compressibility of fillers and the performance of appropriate sealants see 5.
For example, movement joints at 12 m centres should be about 16 mm wide. However, to avoid cracking due to thermal contraction, the spacing between movement joints should never exceed 15 m in unreinforced walls. Closer spacing may be necessary for walls that are less well restrained, e. Where bed joint reinforcement is used, spacings greater than 15 m can be satisfactory, but expert advice should be sought. Present evidence suggests that vertical movement of unrestrained walls is of the same order as horizontal movement.
The brick manufacturers should be consulted. This can be effected by the introduction of a vertical, compressible joint or a slide-by detail. Returns of mm or more should be regarded as having sufficient inherent flexibility to accommodate the stress caused by the opposing forces see Figure Figure 15 Short returns in clay masonry 5.
The ratio of length to height of the panels should generally not exceed As a rule, vertical joints to accommodate horizontal movement should be provided at intervals of between 7. Movement joints need not generally exceed 10 mm in width.
They should be sealed where necessary. In external walls containing openings, movement joints may be needed at more frequent intervals or the masonry above and below the opening may need to be reinforced in order to restrain movement see 5. The design should pay particular attention to long low horizontal panels of masonry, e. External walls of calcium silicate masonry should have a compressible joint to allow for thermal expansion at not more than 30 m intervals.
The degree of movement is dependent upon unit type and, as a rule, vertical joints. In external walls containing openings, movement joints may need to be provided at more frequent intervals, or the masonry above and below the opening may need to be reinforced to restrain movement see 5.
Particular attention should be paid to long low horizontal panels of masonry, e. External walls of concrete masonry should have a compressible joint to allow for thermal expansion at not more than 30 m intervals. Areas above doors and above or below windows may benefit from being reinforced to distribute tensile stresses see 5. Flexible cellular polyurethane, cellular polyethylene or foam rubbers are satisfactory materials.
Hemp, fibreboard, cork and similar materials should not be used for expansion joints in clay brick masonry, but may be used for contraction joints in calcium silicate and concrete masonry.
The width of the joint should be sufficient to accommodate both reversible and irreversible movements, without damage to the seal. Hence the width of the joints should be related to their spacing and to the ability of the sealant to accommodate movement.
Guidance on the selection of sealants is given in BS Certain single-part, moisture cured sealants are best used in joints of small cross-section due to their excessive curing time in thick sections. Optimum performance in butt joints is obtained when the width to depth ratio of the sealant bead lies within the range to for elastoplastic sealants including one- and two-part polysulfides , or the range to for plastoelastic sealants.
Movement joints in masonry walls are generally deep in relation to their width. In order to fill the inner portion of the joint, filler material should be positioned to leave the correct depth to accommodate the sealant.
The sealant should be applied against a firm backing so that it is forced against the sides of the joint under sufficient pressure to ensure good adhesion. The filler material should not react with or adhere to the sealant. If a bond breaker is necessary, it should be positioned between the filler material and the sealant. A crosslinked, closed-cell polyethylene foam provides a suitable combined filler and bond breaker.
The foam should. The reinforcement should be long enough to distribute the stress to a position where the vertical cross-sectional area of the wall is able to accommodate it. Reinforcement should be adequately protected against corrosion see 5. Consideration should be given to the need for slip planes under the bearing of lintels or beams to separate the wall from structural members that can produce a horizontal movement, e. Consideration should be given to the need for lateral restraint, and fire integrity should be maintained.
Cladding, irrespective of the type of masonry units from which it is built, should be provided with adequate lateral edge restraint see 5. Some particular cases of design to limit the effect of differential movement and yet to provide stability of the panel are described in 5. This movement will be in opposition to thermal expansion of the cladding. In addition, in the case of cladding of clay units, there will also be irreversible moisture expansion.
If masonry cladding is built-in tightly between horizontal beams or floor slabs, these opposing movements can cause excessive stresses in the masonry, particularly if there is eccentricity, e. To prevent excessive stress occurring, horizontal compressible joints should be provided to accommodate the differential movement. Such a compressible joint should be provided at the top of any masonry cladding built up to the underside of any horizontal element of the structure or any supporting component fixed to it, see Figure Figure 16 An example of a support system showing provision for movement With cladding of calcium silicate or concrete masonry the differential movement between the cladding and the concrete structure is less.
This is because the long term moisture movement of both cladding and structure involves shrinkage, and thermal expansion of the cladding is the only opposing movement. Provision for differential movement by the inclusion of a compressible horizontal joint eliminates the stabilizing effect of a mortared joint or simple restraint fixings see 5.
Sliding anchor restraint fittings are available see Figure 17 for a typical example. Where wall ties and restraint fixings are fitted between cladding and frame they should be designed to permit appropriate movement. Steel frame structures are not subject to shrinkage movement and so vertical differential movement is due only to thermal and moisture movements of the cladding. For internal walls, if eccentric loading and short returns see 5. Concrete and calcium silicate masonry should not be tied rigidly to the frame, but adequate lateral restraint should be provided.
Movement of the timber frame and movements of masonry in response to thermal and moisture changes are dissimilar. Building details should accommodate the vertical movement between frame and cladding.
For example by: a use of timber frame wall ties that tolerate relative vertical movement between the frame and the cladding; b provision of a gap between the top of the cladding and oversailing frame members such as eaves ladders and the feet of trussed rafters. Window and door frames are usually fixed to the timber structure and project across the cavity and into an opening in the masonry cladding. Building details should accommodate any tendency for joints between the cladding and the underside of sills to close and between cladding and the heads to open as a result of differential movement between the structural frame and cladding see Figure NOTE When a timber platform ground floor is used add 3 mm to the differential movement allowances quoted.
Figure 18 Recommended allowances for differential movement between the timber frame structure and brick cladding. The masonry may be tied to the frame and designed to move with it by permitting limited rotation at the d. Alternatively, the masonry may be designed as a structurally self-supporting wall.
Any connection to the frame should not be fixed in a manner that restricts the anticipated movement. The masonry should be designed not only to resist the stresses due to the imposed load, but also the stresses that can arise from differential movement between the masonry and the frame.
Where their use is unavoidable, panels of slips should be isolated from movement and stresses in adjoining masonry. Building defects are the most common cause of water penetration through the building envelope. The source of water can be from precipitation or from ground water.
The specification, design, detailing and construction of the total wall element should contain provisions for appropriate resistance to rain penetration in relation to local exposure conditions [5]. An assessment of local wall spell should be made see 5. For each type of wall, in any particular building, the most exposed part should be given particular attention as this will affect decisions concerning the choice of design and materials.
Guidance on resistance to rain penetration of different forms of masonry construction and the factors affecting rain resistance are described in 5.
Rainfall varies considerably across the country and is largely unaffected by local features. Conversely, local features such as the spacing and height of neighbouring trees and buildings and whether the ground is flat or steeply rising affect the wind speed significantly. BS allows calculations for different orientations.
Annual average values can be calculated as well as quantities for the worst likely spell in any three-year period. It permits corrections to be made for ground terrain, topography, local shelter, and the form of the building concerned.
BS gives recommendations for two methods of assessing exposure of walls to wind-driven rain, namely the local spell index method and the local annual index method. The local spell index method should be used when assessing the resistance of a wall to rain penetration. The local annual index is intended for use when considering the average moisture content of exposed building material or when assessing durability, the effects of the weather on the appearance of materials and components and the likely growth of mosses and lichens.
Exposure categories defined in terms of wall spell indices calculated using the local spell index method specified in BS are given in Table The indices, derived as they are from inherently variable meteorological data, should not be regarded as precise.
Where assessment produces an index near the borderline between categories the designer should decide which is the most appropriate category for the particular case, using local knowledge and experience. BRE Report BR [6] provides a simplified procedure for assessing exposure to wind-driven rain for walls up to 12 m high. It is primarily intended for low rise domestic buildings, but may also be considered suitable for other categories of buildings of similar scale. This simplified guidance is based on a map that defines zones in which calculations, in accordance with BS , predict similar exposure conditions.
The zones are numbered 1 to 4 and correspond with categories defined in Table The calculations defining the mapped zones in [6] assume worst case conditions and so provide very conservative guidance.
As such [6] can restrict the choice of construction. A greater choice is obtained by more specific assessment using BS NOTE These factors are not listed in order of importance. A greater proportion of the water runs down the face of the walling and can be blown into and through it via paths in the mortar joints, particularly at the interface between the mortar and the masonry units see 5.
Masonry units having relatively high water absorption characteristics will absorb water running over a wall surface in conditions of driving rain. If the duration of the rainfall is short this behaviour can be considered beneficial because it prevents most of the water reaching the mortar joints. However, when the surface of the material approaches saturation point water tends to run more readily down the surface and, as in walls of dense units, can penetrate via paths at the mortar joints.
In Very Severe and prolonged conditions of driving rain, water can be absorbed further into the masonry units and eventually reach their inner surface, first as dampness and then as free water.
Generally rain ceases long before such complete saturation and water evaporates from the wall by the drying effect of wind and air movement. These two modes of action are sometimes referred to as the "raincoat effect", in the case of dense, low absorption units, and the "overcoat effect", in the case of high absorption units. Solid walling can ultimately be penetrated by prolonged exposure to wind-driven rain regardless of the water absorption characteristics of the masonry units. These mortar strength classes are often used in conjunction with dense, low water absorption clay bricks.
This combination is satisfactory but should not be regarded as providing a near waterproof construction see 5. Strong dense mortars such designation i and ii , strength classes M12 and M6, are not suitable for use with some other types of masonry units and selection is governed by other factors such as accommodation of movement, durability and strength.
Designation iii and iv mortars, strength class M4 and M2, are often more appropriate. Of the various mixes recommended for the mortars of each designation, those incorporating lime in their composition show an improvement in bond development. However, in practice, this advantage is not likely to be of great significance. Table 11 shows the recommended minimum thicknesses for both rendered and unrendered single-leaf walls for various categories of exposure as defined in Table With regard to rain resistance a waterproof cladding system as listed in 5.
Where hollow blocks are used in external walls, the use of shell bedding can reduce rain penetration. Table 11 Single-leaf masonry Recommended thickness of masonry for different types of construction and categories of exposure Type of masonry. Masonry units will normally be laid on their bed faces, but some concrete block walls will be built by layingblocks flat; tables for compressive strength are given for this circumstance.
In other cases where units areused under load in another aspect, laid on stretcher or on end, the strength of the units should be determined for this aspect in accordance with BS ,Annex D or the test method prescribed inBS EN When bed joints are to be raked out for pointing, allowance should be made in design for the resulting lossof strength. BS pdf download.
Download infomation Go to download. Note: Can you help me share this website on your Facebook or others? Many thanks! Code of practice for theuse of masonry. Space data and information transfer systems - Security architecture for space data systems. BS ISO pdf free.
0コメント