Brick & Mortar Foundations: What you Need to Know
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If you own a historic home in the Milwaukee area, you likely have a brick and mortar foundation. If this is the case with your property, understanding how to maintain and care for this particular type of foundation is critical.
Brick and mortar foundations require a different approach to maintenance than newer concrete or older stone foundations. Hiring a professional to do this work is ideal; the relationship between the type of brick, type of mortar, and how they work together will determine the longevity and health of your foundation. A professional mason can help you determine how to strike this balance.
Well-made brick has the capacity to last more than 100 years, but it’s the mortar joint – the material between those bricks – that requires more careful maintenance. The average lifespan of a mortar joint is about 25 years – around that time, it is likely the mortar will need to be professionally “repointed” (repaired).
What is “repointing”?
You may have heard the terms “pointing” and “repointing” when it comes to brick-and-mortar foundation maintenance. The difference between the two is small: pointing means adding mortar to a wall built of masonry units (bricks or stone). Repointing means repairing mortar between masonry units.
Methods for pointing and repointing vary and depend on the type of brick and preferred style of the homeowner.
Types of mortars
To protect the longevity of your historic foundation, it is critical to use the right type of mortar. Older bricks are usually soft and porous, meaning they flex under pressure. Wisconsin’s rain and snow cause freezing and thawing of water within the soil, which exerts pressure on the foundation of a home. Mortar that is too rigid will inhibit bricks from flexing naturally, which can lead to cracking. Mortar that is slightly softer than the brick it supports will allow the brick to flex, leading to a longer lifespan of the whole foundation.
Mortar also needs to be breathable, letting internal moisture evaporate out instead of being caught in the mortar and absorbed by the brick, which can lead to damage.
Since 1900, many homes with brick foundations were constructed using a mortar mixture containing Portland cement, which is significantly harder and less breathable than more traditional mortar mixtures.
While a Portland cement mortar mixture may indeed be the right choice for your home’s brick foundation, if it was built before 1900 you will want to call in a professional to give their opinion. There are lots of mortar options on the market these days, some of which contain higher percentages of lime and sand – a better match for old brick.
When it comes to color and style of mortar, you have a lot of options. If you are planning a repointing project on your historic foundation, check underneath eaves and in other recessed areas to get a sense of the mortar’s original color. Then, it’s time to choose the style of mortar joint profile you prefer.
“Mortar joint” is the term for the length of mortar extending across a brick, stone, or concrete block (“masonry unit”). When repointing, a mason usually removes about 2 inches of the old mortar and replaces it with a new mixture. To finish the repair, the mason applies a profile to the mortar while it is still pliable. The most common types of profiles are: concave (or rounded inward – the most common type of mortar profile); weathered, where the mortar is inclined from bottom to top; beaded, when the mortar is curved outward; and vee joint, where the mortar is pressed into a v shape.
Types of brick
You may be surprised to learn that there are many different types of brick. Most historic brick-and-mortar foundations use one of the following three types: soft-mud, pressed, or wire-cut brick.
Soft mud bricks, most commonly used on houses constructed in the 1850s and before, are hand packed into molds, then fired in a traditional kiln. The mortar mixture most appropriate for soft mud bricks is a mixture of lime and sand – no Portland concrete.
Pressed brick, seen on houses built in the late 1800s and after, is made of machine-pressed clay and fired in hotter, more contemporary kilns. The best mortar mixture for these types of bricks is one made of Portland cement, lime, and sand.
Wire cut bricks are of similar vintage to pressed brick, but are cut with wire rather than pressed into a mold. Wire cut brick may be porous or more solid, so the right mortar mixture depends on the specific batch of bricks.
Common pointing/repointing methods on historic homes
While every mason has the opportunity to choose their own process, here is a typical workflow for repointing a brick-and-mortar foundation:
- The mason removes the old mortar up to 2.5 inches into the mortar joint. To do this, they may use a hammer and chisel, a scraping tool, and angle grinder, or a combination of tools.
- The mason then removes any debris from the joint to ensure a good bond between the new mortar and existing brick.
- The mason then moistens the brick – this is a crucial step, as mortar applied to dry brick means the brick will soak up too much moisture, leading to cracks and potential failure of the mortar joint.
- The mason will then apply the new mortar. They may use a mortar bag to insert the mixture or may choose to use a pointing trowel.
- Finally, the mason uses a joint tool to apply the selected mortar joint profile.
Milwaukee’s historic home landscape means local home buyers might find themselves with a brick-and-mortar foundation. This is not something to avoid: while they do require maintenance, a brick-and-mortar foundation that is lovingly cared for can last for hundreds of years.
Here at Towne & Country Building Inspectors, historic home inspections are our passion. If you are looking for a historic home inspector in Milwaukee, look no further. Give Towne & Country Building Inspectors a call to schedule your inspection today.
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