Design of Parapet As Per British Standards - Materials and Construction Details
Materials for Parapet Construction
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1. Bricks and Blocks for Parapet Construction
Bricks and Blocks Dense aggregate concrete blocks to BS EN 771-3 are normally sufficiently frost resistant for use in UK locations. F2, S1 or F2, S2 clay bricks to BS EN 771-1 are recommended in order to minimize the risk of frost attack. Under some circumstances F1, S1 or F1, S2 clay bricks to BS EN 771-1 may be used.2. Mortar for Parapet Construction
A mortar mix of 1 part Portland cement, ½ part lime and 4½ parts sand (a 1: ½:4½
cement: lime: sand (CLS)) is recommended for use in parapet walls constructed from F2,
S1 or F2, S2 bricks. If the wall is built with concrete blocks it is likely to be rendered and a
1:1:6 CLS mortar should be acceptable. If the wall is constructed from F1, S1 or F1, S2
bricks use 1: 1: 6 CLS.
BRE Digest 362 provides further information about building
mortars.
The choice of sand is very important in ensuring a good bond between the units and the
mortar. BRE recommends the use of a well graded building sand with a low fines content.
3. Damp Proof Courses and Cavity Trays for Parapet Construction
Damp proof courses and cavity trays must have good bonding properties to the masonry
4. Cappings and Copings for Parapet Wall Construction
Use frost resistant copings to BS 4729, or other copings to BS 5642. In all instances,
copings must include an adequate overhang and include a drip.
Capping and copings should be capable of being mechanically fixed to the parapet wall.
A number of manufacturers produce suitable systems, including preformed metal and GRP capping.
Render should not be applied to the upper surface of the capping or copings on parapet
walls.
5. Joint Sealants
Joint sealants should be selected according to BS 6213.
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| Design of Parapet As Per British Standards - Materials and Construction Details |
Construction guidelines for Parapet Wall Construction
Stability of Parapet Wall Construction
Wherever possible, parapet walls should not be free standing; they should incorporate returns at each end or be tied into adjacent structural elements. To ensure that parapet walls are as stable as possible, wall ties must be used at the following centres in them: horizontal spacing - 450mm; vertical spacing - 225mm. Where panels are structurally isolated because of the presence of movement joints, slip ties should be incorporated across the joint. The positioning of the slip ties must not affect the subsequent sealing of the joint.
Masonry for Parapet Wall Construction
Follow accepted good workmanship practice guidance given in BS 5638-3 and
BS 8000-3. Use bricks frog up, finishing the mortar pointing with a bucket handle profile.
Use stainless steel wall ties. If there is to be a render finish (usual with blockwork), ensure
that the joints are raked back by 10mm to 12mm prior to applying the render to provide a
good key; with brickwork, do not render both faces of the parapet wall as this is likely to
extend the periods during which the wall will remain damp.
When applying render, dampen the masonry to reduce the initial dewatering of the
render. Protect new masonry from rain, frost and wind.
Positioning of Slip Ties for Parapet Wall
Slip ties should be used whenever a parapet wall abuts an adjacent structural element
and across any movement joints that are incorporated in its construction. The slip ties
should be made from stainless steel. Three slip ties should be positioned through the
height of the wall, and at third points, but not at greater than 225mm vertical spacings.
The upper tie should be positioned in the mortar bed of the course below the DPC.
6The remaining ties should be positioned ⅓ and ⅔ of the distance from the cavity tray to
the upper slip tie.
Loading for Parapet Walls
Parapet walls will be subjected to wind loads. Wind loadings should be calculated
according to the procedures in BS 6399-2.
Where the parapet wall is also to act as a safety barrier the appropriate horizontal
loadings should be calculated to BS 6399-1.
Procedures for designing masonry for particular loadings can be found in BS 5628-1.
Allowing for Movement for Parapets
Movement joints must be incorporated at appropriate intervals, BS 6093. The spacing of
the movement joints in the parapet walls should mirror those in the walls directly below
them, where they are present.
Jointing For Parapet Walls
Joints should be designed according to the procedures described in BS 6093 and sealed
according to the procedures described in BS 8000-16.
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