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When It Comes to Brick Mortar Repair, Stronger Isn’t Always Better!

Aug 6, 2014 4:30:00 AM Christina Wilson

For owners of many historic homes in Washington DC, brick mortar repair is necessary to maintain the integrity and value of the old structures. Masonry contractors in DC who are specialists in historic masonry use mortar for tuckpointing that is softer and more permeable than the bricks.

 

Brick restoration in DC historic neighborhoods involves the craft of removing the old mortar and replacing it with new mortar. In this process known as tuckpointing, the historical features of the building are maintained and enhanced, and its resistance to weather damage is reinforced. While it is commonly thought that a strong mortar works best, the opposite is actually true. When the mortar is stronger than the brick, the wall is susceptible to damage and its durability over time is reduced. Here’s why:

  • Walls in many historic homes were constructed with coal-fired clay bricks and lime mortar. The historic bricks were fired at lower temps and are relatively soft. They can expand and contract as they absorb and release moisture.
  • The original lime mortar was also softer and provided a cushion for that movement. Replacement mortar has to be soft or flexible enough to accommodate movement of the bricks.

The Old House Journal Says...

There are two classes of mortars: those based on lime, and those based on Portland cement. Portand cement mortars are very hard and slow to transmit water or water vapor. Lime mortars are quite soft, and readily allow water and water vapor to pass. While Portland cement is a good pairing with modern hard-fired brick or hard stone, trouble arises when it's used with older, hand-packed bricks. In this pairing, the hard Portland cement mortar will cause soft brick and stone to deteriorate at a rapid pace. Lime mortars readily accommodate older brickwork. When in doubt, use a soft mortar. 

What Does This Mean for Homeowners?

When selecting masonry contractors in Washington DC, make sure that they are specialists in the correct application of traditional materials and methods. If walls are tuckpointed properly, owners can expect the authentic beauty and integrity of their historic homes to last for a long time.

Download Free Homeowner's Guide to Tuckpointing


 

Renaissance Development, a leader in brick restoration and historic preservation, specializes in the restoration of a historic brick building’s mortar joints using traditional methods (tuckpointing) and materials. Contact us for a free site visit and project quote.

Categories: Repair

 

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