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Hirst Conservation undertakes the analysis, repair and cleaning of all types of stone objects ranging from intricate stone carving and sculpture to architectural masonry in materials such as marble, alabaster and limestone.

The services offered for the treatment of stone include:

Survey, research and documentation:

  • Consultancy, survey and feasibility studies to advise clients, including comprehensive condition surveys and photographic and diagrammatic recording of the condition of the stonework, highlighting areas that require replacement, consolidation or other treatment
  • Assessment of any previous treatment documentation or apparent intervention
  • The creation of reports to document any survey, analysis or treatment undertaken, alongside any recommendations or specifications for future conservation or restoration work


Analysis may be necessary to facilitate treatment and cleaning of the stone. Forms of analysis available through Hirst Conservation include:

  • The measurement of moisture levels within the stonework
  • Discrete sampling of the stonework for later determination of its soluble salt content, hygroscopicity, lithology and petrology
  • Environmental recording of relative humidity, absolute humidity (vapour pressure), temperature and dew points. These results, and the relationship between internal and external conditions of the building, will have an important bearing on the stability of the stonework


  • Structural consolidation of areas showing granular disintegration
  • Consolidation of flaking/scaling stone materials by grouting and filleting
  • Pinning of loose or broken elements
  • Mortar repairs to missing areas
  • Application of protective shelter coatings


  • Cleaning of stone is undertaken for practical reasons, such as the removal of biological growths, gypsum, pollution layers or salts, which might otherwise have a detrimental effect on the condition of the stone. Aesthetic cleaning is not generally considered vital to survival of the stonework although it can be an important aspect of treatment in some circumstances
  • Options for cleaning include the use of chemical, reagent or steam methods, micro air abrasive techniques, laser cleaning, the application of biocides or poulticing. The suitability of methods will be determined following preliminary cleaning trials.

Some of our projects include:

  • York Minster – Conservation of monuments
  • Windsor Castle – Conservation of fire damaged stonework.
  • Stable Block, Windsor Castle – Stone repairs
  • London, Hampton Court Palace – Specialist building repair to include brickwork conservation and replacement, stone conservation, grouting and consultancy.
  • Bishop’s Gatehouse, Ely – Conservation of statutory and cleaning with JOS system.
  • Trinity Bridge, Crowland – Conservation of medieval town bridge
  • Temple Newsam House, Leeds – Conservation of ornate stonework
  • Greyfriars Tower, King’s Lynn – Founded 1230-5. Stone cleaning to reveal condition for survey.
  • No 1 Poultry, London – Terracotta conservation
  • Usher Gallery, Lincoln – Marble statues cleaned for loan to Tate Britain