Cast stone units should be designed to minimise on-site cutting. However, if it is unavoidable on site, guidance should be obtained from the cast stone office before proceeding.

Internal treatment

The plastering of stone surrounds internally is not recommended. Where a backing lintel is used it should not be set or cast onto the stone head, but positioned behind and below the top of the head. The inner blockwork should be returned approximately 50mm across the inner back face of the jamb and head. At the cill position, it is a matter of choice whether part of the stonework is left exposed.

Final treatment

After completing the architectural dressings, brush down to remove any mortar spots and apply a vapour permeable external waterproofing liquid, paying particular attention to the joints.

Cleaners

The use of strong acid cleaners should be avoided on cast stone materials. Contamination due to cleaning of higher courses of masonry or other materials should be avoided. Cleaning finished cast stone at the end of the construction period should be in accordance with BS 6270.

Efflorescence

The natural occurring phenomenon know as efflorescence or lime bloom may occur, causing a lightening of the surface colour. It is a temporary situation and will with time disappear as a result of normal weathering.

Repair work

In many cases it is possible to repair chips etc., but advice should be sought from the company before commencing. Since the repair work is normally carried out with mixes very similar to those used in the original manufacture it will therefore take time to weather to the colour of the item.

Heads provide a very appealing method of spanning openings in wall constructions whilst co-ordinating with brick/stonework or other architectural dressings. Self supporting heads can be supplied plain or as a one piece keystone unit with either a straight or splayed perpend. Reinforcement is incorporated for handling purposes only and structural details are required if any head is to be load bearing. The three piece keystone or splayed heads with no bearing should be fully supported by a proprietary box section steel lintel. A minimum bearing of 215mm bearing is recommended when using a 215mm high head and 150mm bearing for a 140mm high head. As a guide 140mm heads are limited to a maximum span of 1350mm and 215mm heads to a maximum span of 2400mm. Bullseye Bullseye windows can be incorporated into many modern designs both for visual effect or to create natural light in stairwells and other areas where a full size window would not be practical. They can be used in conjunction with standard timber (600mm nominal diameter) or metal windows (610mm nominal diameter - 618mm into rebates). They are supplied in four segments for erecting with 6mm joints drilled for an including dowels. In the absence of the actual window they should be built around a temporary .

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