Historic Masonry: To Repair or Not To Repair by Deanna Freer

Historically, masonry is the most durable of all building materials. Masonry is often easier to maintain than its wooden counterparts, but when repairs are necessary, they can be very expensive and problematic. Masonry buildings are susceptible to damage by improper maintenance, poor repair techniques and harsh or abrasive cleaning methods. For the purpose of this article, historic masonry includes stone, brick, cast stone, concrete and concrete block.
Prior to making any repairs on your masonry building, you should take the time to determine what the cause of the problem might be. If this step is overlooked, the damage could continue in spite of repairs. Some causes may include: leaking roofs and gutters, settlement of the foundation or exposure to the elements.

If you believe the cause of the problem relates to the settlement of the foundation, it is important to have a structural engineer or qualified professional look at it. Foundation settlement causes cracks and widening of the joints. It is important to determine if the movement is active or stable. If settlement is gradual or has ceased, the solution may be simply to repoint (replacement of missing or damaged mortar). If settlement is active, you may need to repair the foundation as well as the mortar.

Water is often the main cause of damage to masonry buildings. Rain and snow can lead to plugged gutters, roof leaks and malfunctioning rainwater leaders. This uncontrolled water infiltration often results in the weakening or the disappearing of mortar. It is important to provide proper drainage so that water does not stand on flat, horizontal surfaces or accumulate in decorative features. By insuring proper drainage, your masonry will last longer and not require expensive repairs.

Repair and maintenance procedures for masonry surfaces include rebuilding, repointing, cleaning and the application of coatings. Some repairs are essential as damaged or collapsed masonry will need rebuilding. Proposals for cleaning or the application of coatings should be carefully considered. There could be consequences to these choices and they are quite costly. For example, cleaning masonry may result in the loss of some of the original material and is only justifiable when pollution or dirt is actively causing deterioration.

Masonry should only be cleaned in order to halt a building’s deterioration or to remove heavy soiling (i.e., pollution, dirt and moss). Proper cleaning methods, when deemed necessary, can enhance the aesthetic characteristics and the structural ability of a historic building. Removing years of dirt can extend the life and longevity of a historical resource.
If cleaning is considered appropriate, a very gentle method should be used. The most common method is to use water, detergents and natural bristle brushes. Masonry should never be sandblasted or cleaned with abrasives. These methods erode the surface of the material. Also, chemicals that will permanently damage the masonry, such as acids or solvents, should never be used.

If a masonry building requires repainting, damaged paint should be removed using the most gentle method possible. This is usually entails a soft bristle brush and non-corrosive chemicals. When repainting, the replacement colours should be historically appropriate. Remember, you should not paint a previously unpainted masonry surface, as it rarely complements the design and often drastically alters the appearance of the building.

Repairs to a masonry building can be done on your own, but it is best to consult with a professional who specializes in heritage restoration work or who is prepared to undertake further study of the building. The results of a restoration project carefully planned and properly prepared will be worth the effort. Please keep in mind that the repairs to masonry features should only be considered when there is evidence of deterioration or damage. A change to historic masonry surfaces can visually impact the entire character of the building.
by Deanna Freer