Stone Essentials

Stone Advice

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Ask Ken Howe!
Ken Howe - stone expert
"Natural stone must be allowed to breath and only a microporous sealant will do this."
Natural stone
"If the wrong mortar is used for pointing it can actually erode the stone."
Natural stone
"We are familiar with the detective work required for stone identification, sourcing and matching."
Preserved beauty

Natural Stone Advice and Consultancy

Ken Howe has an affinity with natural stone and regularly acts as a consultant on restoration and other issues to local authorities, ecclesiastical bodies, architects, builders and individuals prior to projects commencing.

Stone is a natural material that has been used in construction and ornamentation for thousands of years but true expertise has become scarce. If used and maintained correctly natural stone will last for centuries but if used inappropriately it can quickly discolour, degrade and erode.

The price of good advice

Expert advice is included in the price of all our projects. If you need advice on a natural stone problem but do not want to commit to a project we will happily provide a quote for consultancy advice.

Sourcing the correct stone and stone maintenance are two areas where poor advice can be very costly. Some basic pointers are provided below and Ken will be happy to provide detailed advice for specific circumstances prior to receiving an order or on a consultancy basis.

The Search for Stone

Britain's complex geological history has produced a diverse range of rock types. Many quarries have been in operation since early times but many more have long since closed and their stones are no longer available. Some operated only long enough to complete a church and a few local buildings.
All stones are classified by 3 rock types:
Igneous- Granite & Whin Stone
Sedimentary- Sandstone & Limestone
Metamorphic- Slate & Marble
We have extensive knowledge of all types, and specialise in the supply of sandstone and limestone. Note: in the building stone trade, the term Marble is commonly used to describe any sedimentary limestone that is hard enough to polish.

Sourcing stone

Finding suitable stone for the repair of historic churches & buildings can be difficult, since few of the original sources survive. We are familiar with the detective work and procedures required for stone identification, sourcing and matching.

If the exact stone is no longer available other options can be considered. In Britain at present there are more than 350 stone quarries producing building stone. Careful matching of an original stone in terms of geology, texture and colour with one of these stones should provide a suitable matching replacement.

There is no real substitute for experience and through our continued inspection and handling of stone from buildings of varying ages and localities we have become experts in our subject. Contact Ken to ensure that the right stone is identified for your project.

Care & Maintenance

Re-pointing

Although suitable for use in modern masonry construction, cement-rich mortars can cause substantial damage when used to re-point traditional masonry. The cement mortars are much harder and allow less evaporation and movement than the lime mortar remaining in the core of the wall. This pointing causes stress and resists any movement in the surface and along with other factors such as salt crystallisation and frost action can often cause rapid decay in masonry.

Moisture

An important feature of sedimentary building stones is their porosity. Pores are natural holes in the stone that allow fluids like rain water to enter and leave the fabric. Some free flow of fluid through the stone is necessary to maintain its durability. It is not advisable to block the flow by using incorrect mortar mixes, nor by applying or injecting unsuitable synthetic fluids and sealant.

Moisture absorbed into the thick walls of traditional building is retained, but only temporarily. Rough textured surfaces of stone, brick and lime renders encourage evaporation. Modern paints, renders and synthetic coatings are often unwisely applied to overcome damp problems and the results can be disastrous. The impervious surface coatings lock moisture in with a consequence of salt crystallisation and stone decay.

Recommended sealant

The sealant we recommend is a water-borne sealer that is micro-porous and oil resistant. It should be applied with a brush so that it saturates the stone surface. It will dry to an invisible finish and will not alter the colour of the stone. Contact Ken for the supply of the right sealant for your application.

Stone cleaning

There are many risks attached to stone cleaning such as sand blasting, sanding and other abrasive techniques. The effect of inappropriate cleaning methods can be seen most clearly in the softening of edges and the loss of detail. Sadly there are many cowboy contractors willing to employ such methods. High risk trade insurance for stonemasons.

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