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At Brick Doctor, we get a lot of Questions and Concerns about Brick & Mortar Cracking. We have Compiled Information on this Topic to help our Community better Understand & Deal with these brick masonry repair issues.
Table of Contents – Click Here to Find Quickly What You Want
What Makes Brick Move?
What about Brick & Mortar Movement Causes Cracking?
Let’s Look at Examples of Brick Expansion causing cracking
Long walls allow Expansion Forces to Magnify Stress
Elastic Deformation impacts building materials including Brick & Mortar
Bricks Grow in Size with Increasing Temperature
How Can We Help You?
Brick & mortar walls move for reasons we will outline below. When brick movement is not properly managed by good design, bricks and mortar undergo stress and crack.
First, we will explore why bricks and mortar crack. We will go into detail about the forces which cause cracking of brick and mortar and discuss how serious a problem this is for you.
Then we will look at images of cracks you might see in your own home.
First, let’s take a minute and understand what makes bricks move
Several natural processes act on bricks and mortar. Let’s look at several of these in greater detail.
Here is a list, courtesy of the Brick Institute of America, showing types of movement in building materials. We will mostly deal with brick masonry below in this discussion.
Brick right from the kiln are moisture free but start absorbing moisture and start expanding immediately.
New Bricks Absorb Moisture & Grow in Size.
Bricks generally increase in size over their service life. The main cause here is irreversible moisture expansion. When bricks are fired in a kiln all the moisture is driven out of the brick.
The immediately start absorbing moisture and grow in size. Unrestrained elements or sections of brickwork will expand vertically from their supports and horizontally from their centers.
Brick right from the kiln are moisture free but start absorbing moisture and start expanding immediately. Image -courtesy of Brick Institute of America.
Kiln fired bricks grow quickly after firing and tapers off after several years. Image courtesy of Brick Institute of America. This process goes on for several years when the bricks finally stabilize at their new bigger size.
What about Brick & Mortar Movement Causes Cracking?
Related Content: Using Expansion & Control Joints to Relieve Stress Causing Brick & Mortar Cracking
Brick and Mortar cracking is caused by constrained brick which are moving by moisture absorption. The only way to prevent brick and mortar from cracking is to design in moveable joints which can absorb the movement at critical points and reduce the stress and strain in the brick and mortar.
The force of the bricks expanding is a function of the length of the wall. This effect is illustrated in an image above. The more bricks in a particular layer the longer that layer of bricks will grow over time. Different length of rows, maybe intersected by window frames and other hard points; create the differential growth rates, and different amounts of constraint on brick expansion, and product the stress in the brick and mortar that creates cracking.
Brick expansion by irreversible moisture absorption and by exposure to solar gain in seasonal temperature changes, (we talk about temperature effects in a bit) cause bricks and mortar to crack when particular design features of your home do not accommodate the natural forces and causes cracks to form.
Building corners, inside and outside, are often where natural forces interact and the effect is cracked brick and mortar.
The longer the row of bricks the more impact from each brick expanding from irreversible moisture absorption. This impact is compounded by forces interacting at outside and inside building corners. Image courtesy of Brick Institute of America.
Certain Configurations Of Brick & Mortar Are Particularly Susceptible To Cracking Due To Irreversible Brick Expansion.
Let’s Look at Examples of Brick and Mortar cracking due to natural Expansion.
You Might See An Example In This Section Similar To A Masonry Crack On Your Brick Home.
Outside Corner Cracks
Brick masonry walls, where they intersect at outside corners, are susceptible to cracking at the head joint which is the name of the outside vertical mortar joint on the end of the wall.
Bricks grow after coming out of the kiln for several years due to to irreversible moisture absorption. Long brick wall sections lengthen and push on the intersecting wall which often produces a brick and mortar crack as illustrated on the left.
We discuss corner cracks in greater detail and more images here.
Oh, and this image also shows corner pop of the foundation. We discuss these just below.
Covering the Flue of a Brick Chimney is essential. It can be a custom cover like this or a simple chimney cap over the flue itself.
This is a great time to Introduce Expansion and Control Joints
Moveable joints at strategic points in brick masonry are the key to controlling brick and mortar cracking due to irreversible brick expansion through moisture absorption. Click here or continue on identifying crack formation in brick and mortar and we will repeat this link to moveable joints later.
Interconnections of Different Materials often cause Brick & Mortar Cracking
Other building materials expand and contract at rates different from that of brick masonry. These differences are important when elements such as window frames, railings or copings are attached to brick masonry. Distress may occur in either material.
Here, you can see where the joint between brick and cast stone window jamb has cracked the mortar. The mortar is falling out of the joint. moisture and failed.
This kind of cracking relates to the corner pops described next. Dissimilar movement creates stress in the brick masonry and cracking can occur.
We examine brick masonry issues with bonding different building materials- in detail here.
We talk about issues with windows and window frames and brick and mortar here.
Corner Pops
Expansion of the Brick can also impact the corner of the slab foundation. This is caused by the expansion of the brick at a corner which had no bond breaker (black plastic which often does not extend over the corners as it should), so the expanding brick and mortar push outward, popping off a corner of the foundation… hence the name, corner pop.
Corner pops are not a structural problem, merely a cosmetic problem, and the repair is an easy one.
Corner pops relate to the dissimilar expansion rates of building materials. Concrete is a hydration cure giving off moisture as it ages and cures.
Concrete therefor shrinks as it ages while bricks expand. This is why the bond breaker mentioned above is so important, unfortunately the bond breaker is often missing at the corner- poor workmanship and the corner pop occurs.
We discuss corner pops in greater detail and more images here.
Cracks around Hard Points
Window frames, door frames and garage door openings are attached to the structural framing but also protrude into the brick cladding.
These points then become hard points constricting the movement of brick and mortar and generate opportunities for cracking.
Brick masonry is quite strong in compression but natural forces that act to stretch the brick will cause cracking because masonry has little tensile strength.
Rows of windows and doorways or garage doors also impact the irreversible brick expansion process by changing the number of bricks in any number of rows of bricks.
Changing the number of bricks in adjacent wythes- what we call horizontal rows of brick- creates stress in the wall that can generate cracking. In this case you will see cracking around windows and entry points.
Cold Joints
Cold joints are breaks in the masonry, usually at projection designs or 45 degree seams, that are typically grouted with mortar. These joints are weaker because there is no brick bond at the intersection of these building construction elements.
Cold joints will not allow for movement; however, they are easily repaired and if they continue to re-crack, expansive materials can be used to re-grout them.
These image shows an inside corner where the mortar joint failed and is in the process adding a backer rod for the installation of an expansion joint.
Cracks at Wall Offsets & Set Backs
When parallel walls not in the same plane expand toward an inside corner without an expansion joint, the movement may produce rotation of the offset and vertical cracks.
Expanding brick can rotate joints and crack mortar at wall offsets.
Mortar is not flexible and will break. This joint is easily repaired, and, if felt necessary an expansion joint can be added to reduce the moving stress.
Cracks at Wall Changes in Height
Changes in wall height, change in wall construction or wall intersections allow natural stressors to concentrate their forces and crack brick.
Brick and Mortar is not flexible and will often break at changes in wall height or wall construction.
A control joint which can absorb expansion or shrinkage, depending on the stresses occurring at this wall change, will absorb this movement and protect the brick and mortar.
Long walls allow Expansion Forces to Accumulate & Magnify Stress
This long wall has allowed the expansion of bricks by moisture absorption to accumulate along the length of the wall. Each brick absorbs moisture and the more brick in a row, the larger the accumulated expansion force at an end
An appropriate number of expansion joints need to be added. Several factors fit into the decision, age of the brick and the number of vulnerable hard points and the condition of the existing cracks. the expansion of the brickwork may not be adequately accommodated.
This may force sealant material out of an expansion joint, as shown in If expansion continues, then cracking occurs at other locations.
The above pulling apart of bricks and mortar are the result of the long wall illustrated above. This wall had several other problems which we will explore.
In walls with openings, such as window or door frames or other hard points, which constrict the length-wise and width-wise movement of bricks by moisture absorption, such diagonal cracks may occur because of the differential growth rates or the stress finds the weakest point and breaks.
Such cracks usually extend from the head or sill at the jamb of the opening, depending upon the direction of movement and the path of least resistance. Because the effects of expansion are cumulative, dividing long walls into smaller segments reduces the amount of movement that the expansion joint has to accommodate.
The changing of wall length around window frames, door frames and garage openings can also cause brick and mortar to crack. in this case, the problem is exacerbated by the change in height of the foundation. The change of lengths of layers of brick allows differential natural forces to act on the brick layers and instigate cracking.
Elastic Deformation impacts all building materials including Brick & Mortar
Brick and Masonry are on the list of materials which deform elastically, but in the real world, stressed brick you notice is cracked. Image courtesy of the Brick Institute of America.
In building structural design, the designer must consider all forces imposed on the structure, which include dead load, which is the basic building materials such as brick, and live loads- a good example of a live load would be humans walking on a floor; and then design for external lateral forces such as wind and snow loads.
Elastic deformation is a reversible change in length, volume or shape produced by stress in a material
Each of these forces create stresses in building materials, which can result in deformations and deflections of the building elements. If a material remains within its elastic range, it will return to its original shape once the applied forces are removed.
Elastic deformation in brick cladding is quite theoretical to Brick Doctor because we get called after brick and mortar cracks. One type of elastic deformation we deal with while repairing mortar is in lintels over garages deforming and cracking the brick and mortar overhead. Brick and mortar is not flexible; stress bricks and they crack.
Brick and mortar is quite strong in compression but tension will pull brick and mortar apart. We will discuss elastic deformation in lintels and foundations below and separately. But first let’s take a moment to clarify what elastic deformation means.
Settling in the brick and mortar over a garage lintel of elastic deformation in the lintel. The brick and mortar quickly left its elastic deformation domain and cracked. The lintel yield and sagged a bit and stabilized. The yield in the lentil stretched the brick and mortar (tension) and the brick and mortar pulled apart.
Replacement of broken brick and cracked mortar provided a reliable fix here, because the lintel stabilized at a new yield point and new mortar filled in the stretch needed to eliminate stress in the brick and mortar. Lintels over garages come in all stages of lintel problems and lintels have to be supported or replaced. Check out flat arches over garages here.
This lintel deflection problem over garages comes in degrees.
The lentil deflects enough to crack brick and mortar but stabilizes and repairs to brick and mortar solve the problem.
Or the lentil can just be poorly supported structurally and stabilization of the lentil is necessary before brick and mortar repairs will be successful longterm.
In other cases the lintel is just too light to be stabilized and has to be replaced. We discuss such situations with flat arches over garages here.
Now let’s discuss elastic deformation in foundations and slab footings
Settlement Cracks from Foundation Movement
Axially loaded elements such as columns and bearing walls shorten in length due to vertical dead and live loads. Walls, beams, columns and building frames deflect horizontally (laterally) from lateral loads such as wind and seismic events, as well as uneven gravity loads.
A foundation footing bears a lateral load just like a lintel but it is continuously supported by the subsoil. In Texas, we have a lot of clay content in our soils and as these soils wet and dry, they expand and shrink.
This expansion and shrinkage can cause elastic deformation but also destructive deformation in foundations and slabs. This is why there is so much work for engineers and Foundation repair companies in North Texas.
The clay content is uneven in the soil so some portions of the foundation can rear up or subside. Settlement cracks on the brick and mortar are the result. Issues with foundations come in several levels of severity.
Foundation cracking is serious and needs to be dealt with utilizing an engineer and/or a foundation company to survey the foundation carefully, determine what is level and add foundation piers to level up.
Here is a settlement crack created by elastic deformation of the foundation. Foundation has not cracked but the brick and mortar above has, and the crack is wider at the top which is evidence that the foundation has settled left or right or this portion of the foundation has uplifted.
Other times foundations are subject to Creep which is permanent plastic movement over time to an uplifting force or a subsiding force in the soil. This Creep will cause brick and mortar to break, but if the foundation movement stabilizes, brick and mortar repairs can solve the cracking problem.
Foundation failure nor Creep is not needed to cause settlement. Foundations flex during wet and dry seasons and bricks often cannot withstand this flexing without attention to proper design.
Because the foundation has settled but stabilized except for minor seasonal variations, the cracked brick and mortar could be repaired with an expansion joint added to absorb future minor movement of the foundation. We cover expansion and control joints in detail here.
The solution, if structural foundation work is not warranted, are the addition of control joints in the area of settling to absorb the foundation seasonal movement.
When you call or contact Brick Doctor, we will talk with you about your brick cracking situation and help determine whether you need a masonry repair operation or you need to talk to an engineer first. You want reliable repairs and we take pride in our workmanship. We do our best to make sure you get the help you need.
Settlement Cracks In Security & Screening Walls
Proper stiffness in a screening fence or security wall is critical to carrying the dead load over the span between piers or the wall with settle and the brick layers will just crack and separate.
Brick Doctor sees a lot of issues with screening and security walls and the same errors of craft and workmanship pop up over and over again.
If you have screening wall problems make sure you have true masonry crafts people to solve the problem once and for all.
The sound restoration of security walls is a complex subject. We cover them in detail here.
Bricks Grow in Size with Increasing Temperature
Sunshine and hot weather also impact brick as shown in the above infographic. Brick has a relatively high temperature coefficient which means brick expands as it is heated. Solar exposure will cause brick expansion and cooling will shrink the brick. Shrinking and expanding of brick on a solar exposed wall will stress brick, particularly if part of the wall is shaded.
Surface temperatures of brick walls may be much higher than the ambient air temperature. Wall orientation to the sun, the color or type of brick in the wall, and possible insulation behind the brick to isolate heat in a section of the wall, or a section shaded and another in full sun- can all impact the effect of temperature on the wall.
It is possible for a dark, south-facing brick masonry wall absorbing sunlight to reach surface temperatures as high as 140 ºF while the outside air temperature is well below 100 ºF .
The temperature range experienced by brickwork is the difference between the high and low average temperatures. In accepted practice, this range is usually taken as 100 ºF and is based on the annual high and low temperature of the exterior ambient air.
Depending on the orientation of the brick wall, the seasonal expansion by such an extreme temperature range could be a factor in brick cracking.
Temperature issues with your brick walls is an issue which needs to be evaluated by your brick repair company you decide to call.
How Can We Help You with Your Concerns about Cracking Brick?
Over the years, Brick Doctor has done just about everything when it comes to repairing and restoring cracking bricks and mortar. We know how to analyze structures, understand the history and age of your home and determine where expansion and control joints are needed to give you your best chance for reliable performance by your brick and mortar in the future.. We know what we are doing. Let us know if we can help you.
Don’t take our word for it. (Check out our testimonials and reviews. And, even better, ask a neighbor for a recommendation. We have done tens of thousands of projects all over the DFW Metroplex since 1986, including for some of your neighbors.
Do you have any particular questions or concerns about a brick and mortar at your home? We can help.
Brick Doctor is always ready to answer your questions, address your concerns or provide an estimate for repairs designed for the scope of your needs.
We look forward to assisting you. Reach out today. Contact us