When it comes to historic masonry restoration, selecting the appropriate mortar for the project is crucial. By considering the building’s existing brick type and strength, one can ensure optimal durability and longevity of the structure.
In this article, the experts from Abbot Building Restoration provide several reasons why ensuring the most compatible mortar is utilized. Without these precautions, you may find that you are left with an even bigger and more expensive problem on your hands.
The strength of brick masonry is a significant factor when choosing an appropriate mortar, especially with a historic restoration project. Generally, historic brick is much softer than modern varieties. Thus, this type of brick can also break and deteriorate quickly if a stronger mortar is applied.
Modern brick is more robust due to high-temperature firing processes that were not available in earlier times. Because of the strength, it should be considered for any historic masonry restoration project – but, again, with caution.
Portland vs. Lime Mortars
Aside from the brick’s strength, the mortar type also plays a prominent role in the success of a historic restoration project.
Portland cement mortar was introduced in 1871 and remains one of the most commonly used mortar types today. However, while Portland mortar is quick-setting, strong, and inexpensive, it is also more rigid and less permeable than lime mortar. If Portland cement is used for historic masonry restoration, it can cause unwanted damage and deterioration to the brick structure. Thus resulting in the need for additional repairs, restorations, and higher costs.
Last but not least, is the difference in water permeability between Portland and lime mortars. Lime mortars are designed to absorb and release water between joints. Portland mortars, on the other hand, are designed to create a waterproof seal. If misused, Portland mortar causes water to become trapped and forced to escape through the brick masonry. This can lead to brick protrusion and ultimately damage and deterioration.
For further information regarding historic masonry restoration, contact Abbot Building Restoration at 617-445-0274.