Masonry walls are very common in some areas and are almost never seen in others. A wide variety of materials can be used. Brick may be clay, calcium silicate (sand and lime) or concrete. Clay bricks are fired at high temperatures, whereas concrete bricks are formed by the chemical interaction of Portland cement, sand, stone and water. Calcium silicate bricks are made using high-pressure steam in an autoclave.
Stone and Concrete
Stone may be as hard as granite or as soft as limestone or sandstone. Concrete may be plain or decorative blocks or large precast panels. Concrete also may be poured in place, although this is more common on commercial buildings than on homes. Concrete may be made into bricks, or it may simulate the look of stone. With few exceptions, these materials are laid up in mortar, and a foundation is needed to support the weight.
Load-Bearing or Veneer
Masonry walls may be a load-bearing part of the structure, or they may just be siding (masonry veneer). The absence of header courses or the presence of weep holes suggests veneer. Load-bearing masonry walls hold up the floors and the roof. In the case of veneer, the building would stand if all the masonry was removed. The structural skeleton is usually a wood frame inside the masonry siding.
Change in Wall Height
Brick walls may get slightly taller after construction as a result of water reabsorption. The increase may be 0.02% to 0.09% of the height and will take place mostly within the first year after manufacture of the brick. Concrete block walls shrink slightly after original construction, by 0.02% to 0.07%.
Bricks expand with higher temperatures and shrink as they get colder. Concrete units expand and contract more with temperature changes than clay does. These dimensional changes are not usually significant in homes, but they are factors on taller buildings. This can be important on three- and four-story townhomes, for example.
Artificial stone may be one of the following:
• masonry units (typically concrete)
• sheets or slices of material embedded in mortar
• material that has been troweled on and then a pattern pressed into it
Some artificial stone is concrete, and some of it is actually reconstituted stone (concrete). Volcanic ash may be added to keep weight to a minimum. The stone also can be a calcium silicate product. The products that are the same size as conventional masonry units require a foundation. Half-inch–thick slices are light and do not require a foundation. Some lightweight products as thick as 2 inches do not require a foundation.
The inspection issues are the same as those associated with masonry or concrete.
Common problems include the following:
• mortar deterioration
• missing weep holes or flashings
• mechanical damage
• bowing walls
Two of the most common problems are cracking and mortar deterioration.
Cracks in masonry units or in mortar
As part of your structural evaluation, you will be looking for cracks. Cracks are much easier to see in masonry units than in the mortar. Cracks in the mortar are usually at the point of connection to the masonry unit, in a natural shadow line.
• building settlement
• freezing damage
• mechanical damage (such as from a vehicle)
• thermal expansion and contraction
Although cracking can be the result of freeze or thaw action, cracking is caused more often by building settlement. Stresses caused by expansion or contraction of the wall as a result of temperature or moisture changes also can cause cracking. Cracked masonry or mortar units may be cosmetic, may be water entry points or may indicate severe structural problems. In the Structure Module of our training presentation (the ASHI@HOME program) on this topic, we outline strategies for evaluating cracks from a structural viewpoint. In this article, we’ll look at cracks from a siding perspective.
The cracks allow water into the wall, which may damage the interior skeleton of the building. Moisture entering the cracks also can result in freeze or thaw damage. Cracks may grow with time at a constant (increasing or decreasing) rate and may open and close as seasons change.
Watch for deteriorated mortar and brick movement in the wall, especially at arches. Although the arches have a structural role, the deterioration is usually limited to the area immediately above the window.
Often, small cracks are best seen by standing back from the wall and looking directly at the wall (rather than on an angle). Several small cracks across the wall surface may indicate considerable movement. One must add up the width of all the cracks. A 1-inch crack would be seen by all home inspectors, but 16 cracks, each 1/16th of an inch wide, and representing the same total amount of movement in the wall, are more likely to be missed.
Mortar deterioration is common on masonry, especially areas that are exposed to considerable wetting. There are several shapes of mortar joints. The illustration shows some common mortar profiles ranked by durability.
Mortar strength. Mortar joints should be roughly 3/8- to 1/2-inch thick on average, with no mortar joint being more than 3/4-inch thick. Mortar is usually slightly softer than the masonry units themselves because if the building moves slightly, the mortar joints will fail rather than cracking the masonry units. It is less expensive to repair mortar joints than to replace bricks. We don’t want mortar that is stronger than the masonry.
A poor bond between the mortar and masonry will allow water into the wall, causing efflorescence and possibly freeze or thaw deterioration.
A poor bond, mortar deterioration or both may result from the following:
• improper mortar mixes or surface preparation
• additives in the mortar
• temperatures too hot or too cold during application
• failure to dampen the masonry units before applying the mortar
• joints being too thin, too thick, incomplete or poor shapes
Deteriorating mortar may result in water damage to the building interior and to the masonry. Repointing is relatively expensive, and it is difficult to match the color and texture of old mortar with new. Care also should be taken not to leave mortar on the masonry surfaces.
Check the mortar joints for crumbling, failed bonds between the mortar and masonry, and check for very soft mortar. Dragging a key or screwdriver across the mortar joints can give a good indication of how soft the mortar is. There is wide variation, but with a little bit of practice, you will be able to evaluate which mortars are acceptably hard and which are soft enough in which to carve your initials in with your fingernail. Surprisingly, some very soft mortars stand up well. Remember that virtually all old houses have areas where mortar could be improved.
Tip of the Iceberg
This article is an overview of masonry wall surfaces, with brief descriptions of the differences between brick veneer and solid masonry. We also outlined two of the most common conditions associated with masonry surfaces—cracks and mortar deterioration.
In the ASHI@HOME program, we dive much deeper into this topic and provide detailed explanations of other problems. In the program, we also discuss masonry walls from a structural standpoint. We encourage you to learn more by taking part in the ASHI@HOME program.
Here are some other articles related to brick or veneer:
Solving a Basement Leak Puzzle Involving Brick Veneer
Inspecting Residential Brick Veneer