The publication of a British Geological Survey (BGS) Factsheet on hydraulic lime has been delayed by comments received during consultation.

Several Factsheets have been produced by the BGS as stand-alone annexes to a report on mineral planning for the Office of the Deputy Prime Minister as part of the current review of planning of which the Capita Symonds report 'Planning for the Supply of Building Stone in England & Wales\' forms part.

These Factsheets have been published by BGS on their website (www.mineralsuk.com). Generally they are uncontroversial, succinct (5-10 pages) single mineral reports covering, for example, fluorspa, industrial dolomite, potash and so on.

The hydraulic lime report is different in that it covers a product rather than a mineral. Ian Brocklebank, chairman of the Building Limes Forum, says: "It\'s rather good as far as it goes. But it's basically rather out-of-date."

And Mike Farey, the man behind HL2, the only commercial English producers of hydraulic lime, feels that, as a planning document, the report could prejudice authorities away from giving permission to open new sites for the production of natural hydraulic lime.

Both men have made submissions to the BGS setting out their reservations and BGS, who wanted to publish the report before the end of this financial year because no provision has been made to pay for it in the ODPM\'s budget next year, say it could be delayed beyond the deadline.

Mike Farey is particularly sensitive about planning because he had an application to open a new lime kiln in Somerset rejected on appeal two years ago. He is currently moving his operation to Singleton Birch, a large independent lime producer near Brigg in Lincolnshire who supply specialist limes for iron and steel production, cleaning coal-fired power station emissions and for farming.

Singleton Birch extract nearly 2million tonnes of limestone a year. Mike Farey expects to produce about 5,000 tonnes of hydraulic lime in his first year\'s production. Almost all hydraulic lime used in the UK is currently imported - about 14,500 tonnes of it in 2003, according to Customs & Excise, mostly from France but also about 4,000 tonnes from Ireland.

But that underestimates the true level of demand now, says Ian Brocklebank, because of a high level of growth in 2004. And he believes the BGS have not taken into account in their report factors that could see even greater growth in demand in the future.

The report describes hydraulic limes as being a "niche market" largely in the conservation section, but Ian says: "We are now discovering these materials have a quality that make them much more interesting for other uses."

He is particularly referring to research carried out by the BRE on hydraulic lime mortar used with hemp to make walls of houses. Calculations show the walls would not be as thermally efficient as conventional cavity insulated walls, but BRE have discovered that when the walls are actually built they perform more efficiently than conventional walls.

There is speculation, though no conclusive evidence, that the improved performance is the result of there being no interstitial condensation in hemp/lime walls.

Ian also says other recent research shows that although hard, Ordinary Portland (OP) cement was developed in 1824, until the 1940s mortars, and the masonry used with them, were much softer and more permeable than they are today, making lime mortars more appropriate for the repointing and repair of many more buildings than had previously been thought.