External masonry walls

6.1.10Stone masonry

Stone masonry shall be constructed to an acceptable standard, including the performance standards for brick and block where applicable. Walls shall be capable of supporting the intended loads and have appropriate resistance to the adverse effects of freeze/thaw.

Stone masonry should comply with the following:

Stone for masonryBS EN 771-6 ‘Specification for masonry units. Natural stone masonry units’.
Cast stone masonry unitsBS EN 771-5 ‘Specification for masonry units. Manufactured stone masonry units’.
or BS 1217 ‘Cast stone. Specification’.
Stone masonry, natural or cast BS EN 1996 ‘Design of masonry structures’. PD 6697 Recommendations
for the design of masonry structures to BS EN 1996
Stone for copings and sillsBS EN 12059 Natural stone products. Dimensional stone work. Requirements

Stone masonry as the outer leaf of a cavity wall will be acceptable where it:

  • provides an adequate weather-resisting structure in conjunction with any brick or block backing, and/or vertical DPMs
  • complies with the guidance in this chapter for brickwork/blockwork
  • complies with BS EN 12370 or has evidence that it is not susceptible to salt crystallisation when used below DPC level
  • follows good local recognised practice to provide a high standard.

Where squared or random rubble is used it is important that the stone masonry is “ brought to course” at regular intervals of not more than 450mm. Bedjoints of up to 25mm wide would be acceptable, and the selection and installation of the correct wall ties should be carefully considered.