The issue of stone repair is a popular topic on our website. We have encountered problems with Lithomex on several buildings. One building in particular showed the application of Lithomex on several different occasions, to wildly varying standards of workmanship, from good to poor.
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Lithomex repairs, more correctly termed a "plastic repair", can appear to be a simple and practical solution to stone erosion, however, to carry out the repair properly and to good standard, so that it looks goof and will be durable, the work requires care in both preparation and execution. As a result, the cost to carry out a Lithomex repair to a good standard can often end up being similar to that of actually replacing defective stone with new stone.
Access to the carry out the preparation, execution and aftercare, either through scaffolding or mobile platform, is the most expensive part of the repair and this puts pressure on the contractor to reduce the time on site. Often, preparation and aftercare are not carried out with an appropriate level of care and attention. A low cost Lithomex repair will be a poor repair that will not last. When a poor Lithomex repairs starts to crack or detach from its substrate, water will enter that can result in further erosion of the stone, but this is now hidden from view.
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While carrying out the repair is one consideration, there are also implications for the future repair and maintenance of the building. Lithomex can disguise the condition of the underlying stonework and conceal problems. When it becomes necessary to do an inspection in the future, it introduces a higher level of uncertainty when trying assessing the condition of the underlying building fabric.
When looking forward, if further Lithomex repairs are carried out. It will gradually become ever more difficult to assess the condition of the fabric, when presented with numerous repairs carried out at different times. Is there a common underlying problem that hasn’t been resolved.
Lithomex should be considered a short term repair, with a limited lifespan. If you encounter a building with numerous repairs, carried out at different times, you have to reflect on whether the point has been reached where stone replacement will be required across quite a large area. The past repairs may therefore have reduced costs in the short term, but have ended requiring a more costly intervention later on.
The preference should therefore be for stone replacement rather than Lithomex repair.
Lithomex repairs should be restricted sheltered areas and used in small, isolated areas, within a single stone block and only after the underlying defects have been fully diagnosed and resolved. The repair should be documented carefully to assist future fabric inspections. The application of Lithomex to areas spanning multiple blocks of stone masonry should be avoided.
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MAAC studio are accredited conservation architects, PAS 2035 Retrofit Co-ordinators and Principal Designers working with traditional buildings throughout Scotland.
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