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Key to Testing the Condition of Your Mortar

Jan 21, 2021 11:44:11 AM Christina Wilson

If you've got a brick home, you are undoubtedly aware that brick is not only beautiful but one of the most durable and long-lasting materials for outside structures and facades. Still, over time, mortar breaks down and will eventually need to be replaced. You need to know how mortar works, how to spot mortar deterioration, and what to do about it.

Facts About Mortar You Need to Know

One of the simplest and most effective ways to test the condition of mortar involves a key. We’ll get to that, but first, it helps to understand what to look for and understand about mortar:

  • Mortar is – The bonding and connecting material that keeps bricks from rubbing against each other in various building and hardscape structures. Ideally, mortar should be a bit softer in density than the brick. This softer mortar allows a cushion that gives enough to prevent too much pressure on the brick material, preventing cracks and other damage to the structure. 
  • Lime vs. Cement – For most historic brick buildings (pre-1930’s), a mixture of lime and sand were used with clay bricks. Certain kinds of cement are compatible with bricks manufactured today. Some types, such as Portland cement, are extremely hard and often used - with harmful results to old brick -  for patching mortar joints instead of historically-appropriate tuckpointing.
  • Cracking and softening – Lime mortar will crack over time with pressure, but it's easier and more cost effective to repair than replacing cracked bricks. Moisture can also soften mortar, reducing the strength and sealing quality of the brick structure. Mortar deterioration is normal, but with proper maintenance we’re talking every 50-100 years. 

Signs Your Mortar is Deteriorating

If the wall or structure is close to 100 years old and there is no evidence of recent tuckpointing, you can expect to find some missing mortar or other erosion. There are ways to diagnose possible deterioration to your mortar that will need to be addressed:

  • Visual inspection – Start by looking for previous tuckpointing or repairs. Large walls exposed to weather, areas near or below drain spouts, eaves along the roofline, and the wall-ground line are common areas to spot water damage. 
  • Mortar shape and depth – Check large areas for inconsistent shaping of mortar joints, crumbling, erosion, or depths more than ¼" from the mortar's original level.
  • Dig in with a key – Drag a metal key over or into the mortar joint between bricks to see how soft it is. If it penetrates or crumbles easily, it's likely a lime mortar in need of replacement. The best time to try this is after a good rain or harsh weather. Solid mortar that doesn't penetrate and has no damaged bricks around it is probably ok, especially if the mortar is light-colored.
  • Rock-hard mortar – When performing the above “key” test for mortar density, if the mortar is rock hard, greyish in color, and denser than the brick around it, that could indicate another type of problem. The original lime mortar has likely been patched with Portland or other hard cement, which will cause damage to the bricks around it. Look around for nearby brick cracks, spalling, or further damage, and make a note to have that addressed as well.

Mortar Maintenance

Maintaining an old house takes constant attention. Once you know that mortar deterioration or hard cement patching is present, you will have to address it. Ultimately, deteriorating mortar calls for tuckpointing, or repointing, to restore the original mortar application's look and function to historical standards. It's a job best left to professionals.

 

Your brick structures and building facade can last for centuries if given the proper care. A critical aspect of that care is making sure your mortar is in good shape. Renaissance Development professionals are experts in restoring and maintaining historic brick homes and structures. Contact us for a consultation regarding the care of your brick home or structures today. 

 

Categories: Historic Preservation, preventive maintenance

 

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