Repointing historical masonry structures
Whether it is stone, brick, concrete block or terra cotta maintaining the mortar joints on a masonry or masonry-clad building is important to esthetically and physically preserving a structure.
Mortar joints ensure that the building envelope continues to perform as a barrier to the elements. Much research has been done to analyze the destruction caused by the use of inappropriate mortars and pointing methods on historical structures.
Mortar serves many purposes in masonry construction, but its main function is to make the wall assembly watertight. Mortar must be softer and more porous than the surrounding masonry units, thereby allowing it to accommodate contraction and expansion and providing a route for moisture to escape.
The colour, texture and profile of the mortar joints also contribute to the appearance of a historical structure.
Repointing is the process of removing the outer deteriorated layer of mortar from the joints and replacing it with new mortar. Repointing deteriorated mortar joints, however, is more complicated than it may seem. If done incorrectly, it can lead to an unsightly mess, deterioration of the historical fabric, serious loss and water infiltration into the building. It should be noted that while the mortar joints themselves are an important part of the building’s historical fabric, they are meant to be a sacrificial element of the wall assembly. In other words, mortar – unlike masonry units – is meant to deteriorate over time.
Consequently, it is understood that historical masonry structures will require repointing periodically. It is important that repointing is correctly done since improper repointing can cause physical damage to the masonry units themselves, which are more difficult and expensive to repair.
The high, compressive strength of the mortar, compared to the masonry units, has caused the bricks to spall, leading to irreparable damage.
When properly executed, repointing masonry joints conserves the historical character of a building while preserving its physical integrity. Proper maintenance, should ensure that any new repointing work has a long service life. For Your confidence we have been trained properly in historical conservation. We can help identify the cause of mortar failure and assist in the preparation of specifications for the work. When correctly done, repointing will contribute to the architectural character and long-term preservation of your historical masonry structure.