Hydraulic Limes (not correct image)
The conservation and restoration of coral stone buildings requires knowledge of mortars used in construction as well as those compatible for the repair of these historic structures.
Untold damage has been caused worldwide by the use of harsh, dense mortars or cements and synthetic materials which are unsuitable for use on soft stone structures. Salts attack, stone erosion, rising damp and decoration decay are all avoidable if sympathetic materials are utilised in restoration.
As air conditioning is increasingly used, the necessity for the external pointing medium or render to be capable of stabilising the wall is increased. Otherwise any moisture that penetrates the coral stone will be drawn inwards as the high pressure externally moves towards the lower pressure internally. Salts, decoration and mortar decay will all be common under these conditions.
Natural hydraulic lime will never become harder than the stone it is being used to repair. The open pore structure of lime ensures that vapour and moisture are extracted from the wall to stabilise salts which are primarily the phenomenon that causes cements to detach along with the resultant damage to the stone. Specially formulated products are used at the base of the structure to extract rising damp as it forms rather than allowing it to condense and form into salt. Cellars and other areas with positive pressure can be treated in the same way with Unilit 30 to stabilise the salts and dry out the wall.
Over the four years since introduction, Unilit Natural Hydraulic Lime has been used in Barbados on conservation projects for schools, hotels, churches and offices. These provide testimony to the efficiency of the products.