The Official Publication
of the Mason Contractors
Association of America
Restoring Indiana limestone on buildings and structures that have been damaged by age, neglect and use.
Since well before Indiana became a state, its massive deposits of limestone have provided building materials for homes, churches, banks, office, government and university buildings. Famous structures made with Indiana Limestone include the Empire State Building, The Tribune Tower and the US Department of Commerce.
Indiana Limestone was a favorite building material during the Art Deco period as new milling machines made possible the distinctive designs of the day. After the Great Chicago Fire, it was discovered that structures built with Indiana Limestone survived remarkably well.
While durable, Indiana limestone can be damaged by age, neglect or heavy use. Alkali stains can cause discoloration when alkali-charged moisture permeates the limestone from its back or bottom bed. Nearby concrete is often the culprit. Efflorescence can occur when moisture picks up sulfates of sodium, calcium, magnesium, iron or potassium from within the wall. This can cause the formation of a whitish bloom or powder on the stone’s surface, flaking and exfoliation.
Acid-charged moisture can cause even more severe damage to limestone surfaces. Over time, acid rain can break down the softer, more porous and chemically sensitive limestone veneers. Because limestone is less resistant to damage from oils, acids, alkali or other chemically charged liquids than marble, granite or other masonry, large sections may need to be replaced over time, especially if the original limestone was installed improperly.
If damage is so severe that the limestone must be replaced, the task can be problematic, especially if the limestone is carved or etched, and particularly in older structures where the old pattern may no longer be produced by the manufacturer. In other cases, the damaged area may be part of an intricate Art-Deco motif or is designed as part of a custom theme created by the architect. Fortunately for restorers, these designs can be copied perfectly and reproduced on Indiana limestone veneer trim and replacement stonework, thanks to a variety of remarkable technologies. Indiana Cut Stone has extensive experience creating perfectly matched replacement stone for Indiana Limestone restoration projects.
How the restorer handles damage to and repair of Indiana Limestone can make all the difference between a good job that lasts and a marginal one that does not. The Indiana Limestone Institute of America recommends that very small chips and snips be left alone, since they don’t detract from the appearance of the finished work, especially if they aren’t at eye level. Limestone fabricators may use specially designed limestone cements to restore large chips during manufacturing. In restoring a damaged surface, if the chip can be found, it may be possible to restore it to its place with the same thermo-setting resin adhesive, or cyanoacrylate "superglue” that the manufacturer uses. In areas not usually visible to the public, a small square void can be cut into the stone and a “Dutchman,” or matching plug, can be installed to fill the void. The Dutchman is secured with thermo-setting resin.
Cracked stones should be replaced, especially if the structural integrity is suspect. If the stone is not load bearing or is impossible to remove, it also can be repaired with thermo-setting resin.
Getting the support structures right
The Indiana Limestone Institute of America produces a number of free publications available for contractor use, including a booklet on limestone repair that has a great deal of information on protecting and restoring limestone building features as well as a booklet on proper installation techniques.
Kathy Baker-Heckard is president of Indiana Cut Stone. Visit www.indystone.com/publications-indiana-limestone.htmlfor a copy of the Indiana Limestone Handbook.
|Last Updated on Friday, 09 November 2012 11:13|