Construction Specification

Movement Joints - In common with most building materials calcium silicate brickwork is subject to movement and provision should be made for this in design. In general, vertical contraction joints should be provided at intervals of 7.5 to 9.0 metres. Maintaining an aspect ratio not greater than 3 to 1 is also important and bed joint reinforcement above and below openings can be employed to distribute stresses built up from all sources of movement associated with the overall structure.

Mortars - Designation (iii) and (iv) mortars e.g. 1:1:6 and 1:2:9 Cement: Lime: Sand mixes are suitable. The choice will depend on such factors as structural requirements, degree of exposure, sand grading and general site conditions.

For work above dpc the use of a 1:2:9 mix is preferable and in accordance with the requirements of BS5628: Part 3: 1985, Table 13 (C.1 and E) - provided that masonary is protected during construction from saturation and freezing.

The use of too strong a mortar should be strictly avoided and with the exception of use below dpc or in copings, no mix should generally be stronger than 1:1:6. For work below dpc, sills, copings and earth retaining walls a 1:1/2:4/1/2 mix can be used. Where sulphates are present in the ground water theuse of sulphate resistant cement in the mortar may be necessary. Alternative mortars using admixtures, although generally not as good, may be used.

Storage and laying - Bricks should be laid in a reasonably dry condition. In very dry conditions easier laying and improved adhesion may be achieved by adjusting mortar consistency or dipping bricks briefly in water just before use. Do not soak bricks in water. Cover new brickwork at the end of the day, especially if rain is likely. Avoid prolonged stacking on site. Stack clear of the ground and protect from rain saturation and soiling.