Love Your Limestone

by Christopher Swan, AIA

The historic Bates County Courthouse in Butler, Missouri is a magnificent limestone building. It is a beautiful Romanesque Revival structure built 1901-1902. As a preservation architect, I truly appreciate the order and care that took place during the design and construction. In fact, this design was so popular at the time it was repeated in Andrew, Johnson and Lawrence counties in Missouri.

I just spent a day going through this building’s exterior with a fine tooth comb in preparation for a masonry restoration. The Commission has already performed some significant restoration work like the restoration of the clock tower, roofing repairs, replications of the Lady Justices, and refinishing the wood floors. All in all it looked great. However, as I stood analyzing some cracks in the historic limestone exterior, I realized that there are some simple things that building owners need to be aware of if they have a historic limestone structure.

You must perform annual checks of the masonry. While it is reasonable to expect to re-point your mortar joints every 50-75 years, the climate in the Midwest is especially hard on limestone buildings. Limestone is relatively soft and particularly susceptible to the freeze/thaw cycle. Regular masonry assessments are best done in the spring after winter has taken its toll. The things in particular you need to look out for are spalling on the face of the stone, loose or empty mortar joints, new cracks, and excessive staining from water. All of these are indicators that freeze/thaw or settling has damaged the integrity of the stone.

Now, if these are present, immediate attention is warranted. The reason for this is that water is the enemy of buildings and will continue to attack and undermine the integrity of the building’s enclosure if these issues are not addressed. I recommend that you have a specially qualified architect or a proven masonry restoration specialist that can conduct these regular checks and prescribe maintenance repairs that will prevent long term damage.

In my next installments, I’ll provide more information on specific types of maintenance that can be done like reporting and repairs.