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4.1 Structural Considerations
Typical detail of non-loadbearing Cast stone is often used for structural (i.e. structural). With decorative heads it is
cast stone lintel construction elements within a building. The inherent important that they are used in conjunction
strength and density of both semi dry and with a steel support or lintel as they are not
Typical detail of self-supporting wet cast material often exceed requirements able to carry additional loads other than their
cast stone lintel construction by a comfortable margin. However the own self weight. With structural heads, the
structural characteristics of cast stone loadbearing capacity will be specified by the
Typical detail of loadbearing produced by different manufacturers will manufacturer. In cases of uncertainty, the
cast stone lintel construction vary and the supplier should be contacted at manufacturer’s advice should be obtained.
an early stage of the project.
Steel support lintels are normally used
As a general guide, cast stone components below the decorative head to support the
can be in compression or tension. Products head itself and the entire brickwork load
intended for use in compression e.g. quoins, above. There are however, cases where
string courses, ashlar and columns are it is desirable to fit the support lintel over
generally not classed as structural units. the decorative head so that the head is
Items such as lintels, which are subjected self supporting while the lintel carries only
to both compressive and tensional forces the load of the brickwork from above. This
should be specified with care. Lintels can should not be done without first consulting
be supplied as either non loadbearing the UKCSA manufacturer.
components (i.e. decorative), or load bearing
4.2 Building Movement
The control of movement should be to BS EN 1996-1-1: 2005 and Section 6.5
assessed at the design stage since all Mortars.
building materials are subject to dimensional
change during and after construction, due Any settlement that occurs can put
to moisture movement, cyclic thermal increased loads on some elements of the
movements, and chemical action ( i.e. building, in the case of cast stone this
carbonation). Deflection under load, ground would apply for example to one piece cills
movement or differential settlement may and built-in thresholds. It is good building
also have to be accommodated. This in practice to bed only under the stooled
general can be overcome by the use of ends of these units and to point up the
movement joints, bed joint reinforcement remainder of the open bed joint at a later
and the correct specification of the mortar. date with a mortar of the same strength.
Alternatively, where practical, temporarily
To reduce the problems with movement, bed the cills in a lime:sand mix until the
ideally the designer should only specify walls are completed, loaded and any initial
mortars of strength classes M4 and M2 settlement has taken place.
[designation (iii) and (iv)] (see NA to BS
EN 1996-1-1: 2005, Table NA.2). Strong Further reference should be made to BSI
mortars, wherever possible, should be Standards Publication PD 6697: 2010 and
avoided as these can introduce too much BS 5642: Part 1:1978.
restraint into the masonry panel which
could induce cracking. 4.2.1 Differential Movement
For further information please refer to NA Due regard should be given to the possible
effects of differential movement between
