In the past, masonry walls that were weight-bearing or too large felt the brunt of natural disasters, high winds, shoddy work quality, and other factors. When not properly reinforced, masonry walls collapse, often bringing whatever is on top of them down with them.
That’s a dangerous proposition, so modern building codes now require sufficient reinforcement to make sure masonry walls can stand the test of time.
Usually, masonry walls today are reinforced by steel. Steel is extremely strong and durable, so it goes a long way keeping weight-bearing walls sturdy.
The reinforcement requirements are part of the National Fire Protection Association (NFPA) regulations that govern how strong a masonry wall has to be to withstand earthquakes and other dangers to avoid catastrophe.
The strength of the reinforcement measures will depend on how large the masonry wall is and how much weight it’s expected to bear.
Reinforced masonry is used across the country in commercial, industrial, and residential structures. It’s an affordable, effective solution that’s easy to build and durable in many different use cases.
Horizontal or Vertical Reinforcement
Masonry wall reinforcement requirements can be met by applying vertical or horizontal reinforcement. These days, reinforcement is put in both weight-bearing and non-weight-bearing masonry walls.
Horizontal reinforcement often involves laying steel trusses inside the mortar joints between layers of brick, stone, or concrete block.
Some builders also prefer using bond beams for masonry wall reinforcement requirements. Bond beams look similar to a normal concrete block or concrete masonry unit (CMU), but they have horizontal cores that allow for steel beams to be inserted along the length of the wall.
They’re great for distributing the weight of a wall, so they’re often inserted at the midpoint of a wall. The bond beams usually have two openings in each CMU, allowing for two bars of reinforced steel.
Vertical reinforcement in masonry walls follows the same general principle of horizontal reinforcement. Instead of the bond beams, though, reinforced steel is inserted in the core of CMUs as the wall is erected.
They are then grouted so they’ll stay firmly in place. Vertical reinforcement bars prevent the wall from shifting under its weight once they are grouted in place.
The vertical rebar runs the height of the wall for increased reinforcement. Multiple bars of steel can be used in each vertical reinforcement line for added strength.
Reinforcing Exterior Masonry Walls
Another common way to fulfill masonry wall reinforcement requirements is to place rebar between the weight-bearing CMUs in the masonry wall and the exterior masonry facade.
Typically, the non-weight-bearing exterior facade and the weight-bearing masonry wall are separated by a matter of inches filled with air or insulation. Steel trusses are inserted into that space on the outside of the weight-bearing wall to increase stability.
The trusses also connect the weight-bearing wall to the exterior brick or stone facade using steel ladders. The ladders connect the walls but still give an inch or two of space in the cavity.
This helps manage the expansion or contraction of mortar and the walls over time and during changes in weather conditions.
Properties of Masonry Units for Reinforced Walls
Not only do masonry walls need to be reinforced by steel bars or trusses, but the masonry units themselves also need to meet minimum standards. Both solid and hollow masonry units that are built from portland cement are governed by the ASTM C90 that lays out minimum thickness requirements.
The ASTM C90 specifies, for instance, that CMUs should not shrink more than 0.065%. Anything greater than that will likely result in cracks that will weaken the CMU and the overall masonry wall.
It also places strict limits on the amount of water that masonry units can absorb to prevent breakdown over time. Without the right masonry units, no amount of rebar or which mortar strength you select to use will matter much.
An earthquake, typhoon, or another natural disaster will damage the blocks or bricks themselves to the point they crumble and the wall deteriorates.
Reasons for Masonry Wall Reinforcement
Anyone living or working inside a masonry building wants to know that the walls are strong and won’t collapse. Reinforced masonry walls are built to withstand earthquakes, shifts in ground surfaces and things like floods or strong winds.
Additionally, reinforced masonry walls stay up longer when there’s a fire, so people have more time to evacuate a building or home. The greater the amount of reinforcement, the longer the time will be before a structure will collapse.
One thing masonry wall owners need to be aware of is that cutting or removing any of the vertical or horizontal reinforcement will significantly decrease the strength of the entire wall.
Sometimes, fire rescue crews have to cut rebar to get inside of a building to evacuate people or fight a fire. When rebar is cut, it may be necessary to renovate the entire wall with new reinforcement to make sure there is enough strength in the wall again.
Reinforced masonry walls should be tested on occasion to make sure weight-bearing walls are still structurally sound. You don’t want to build a wall only to have glaring weaknesses in the reinforcement pop up years down the road.
Thankfully, there are some simple ways to test the quality of reinforcement and whether your masonry wall is at risk of collapse.
There are several tools available for purchase to help. Home improvement stores sell surface penetrating radars that ping inside walls to look for cracks, voids and other items of concern.
Even something as simple as the sounding method, whereby you tap a masonry wall with a hammer to listen for differences in the response sound can help identify areas of concern where maybe grouting has shaken free.
Others use ultrasonic imaging and more advanced techniques for more thorough checks. Whatever you do, it’s a good idea to schedule reinforcement checks annually or after a natural disaster to ensure masonry wall reinforcement requirements are still being met.