Thermal Expansion Cracks in Brick Walls & Foundations
BRICK WALL THERMAL EXPANSION CRACKS - CONTENTS: How to recognize, diagnose, & repair or prevent brick wall or foundation cracks due to thermal expansion. Factors that determine the extent of thermal expansion damage to a brick wall or structure. Absence of control joints or expansion joints in long brick walls leads to extensive cracking damage. Photographs of brick wall crack damage attributible to thermal expansion
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Brick wall cracking due to thermal expansion:
This article describes extensive damage that can be caused to brick structures due to thermal expansion of long brick walls lacking expansion joints. How to recognize, diagnose, & evaluate thermal expansion cracks in brick walls &: brick foundations
and how to distinguish between this type of cracking failures and other cracks and movement in masonry foundations or walls, such as
concrete, masonry block, brick, stone foundation
damage due to impact, settlement, frost or water damage, and other causes.
Types of foundation cracks, crack patterns, differences in the meaning of cracks in different foundation materials, site conditions, building history,
and other evidence of building movement and damage are described to
assist in recognizing foundation defects and to help the inspector separate cosmetic or low-risk conditions from
those likely to be important and potentially costly to repair.
How to Identify, Diagnose, & Evaluate Thermal Expansion Damage to Brick Walls
Thermal expansion failures in structural or veneer brick walls: is a topic misunderstood by many builders, masons, engineers, architects, and inspectors.
As Dave Wickersheimer, R.A. P.E. and masonry failure expert has pointed out, brick "grows" in size indefinitely [though
probably most of its size increase is early after it's manufacture.]
But a separate factor that can cause very large movements and
extensive damage to brick structures or brick veneer walls is the thermal expansion which occurs across a long or tall brick wall
when that wall is heated by sun exposure. The photographs here show significant thermal expansion damage in a long brick structure
when we first photographed
it in 1989. We visited this site again for an update in June 2007.
This brick veneer wall was built over a concrete block building.
The brick veneer was attached using normal steel strap
methods and the brick veneer was also reinforced at intervals using a horizontal steel wire. But the wall, more than 100' long, was
built without a single expansion joint.
As the south-facing wall of this building heated in summer sun the wall grew in length
until it pushed out the East and West building corners at their tops for a total of nearly 3" measured by dropping a plumb line from each building corner.
The veneer movement produced a variety of damage, including:
Significant breaks and gaps at vertical brick mortar joints due to thermal expansion and perhaps some frost and water damage.
Horizontal sliding breaks in brick mortar joints, exposing reinforcing wire to rust, exfoliation, and additional damage from those forces
as the exfoliating wire produced still more pressure on the mortar joint.
Step cracking following mortar joints near the building corners and where the wall movement was resisted by first story intersecting brick walls abutting at right angles the middle section of the long brick wall.
Cracks and broken bricks, and damaged windows at intersections of brick walls and these openings. Additional
window damage is shown in the color photograph lower on this page.
Cracks in the interior concrete block structural wall were observed in the building interior
Leaks and water entry and some frost damage and related loosening of the brick veneer at various locations around the building but were
most severe in areas exposed to thermal expansion of long brick veneer walls.
We were surprised that there was not more extensive damage to the structural walls themselves, and we urged the building management to consult
an experienced mason for further inspection and repair. We expected the mason to cut vertical expansion joints in the wall and to seal these
joints with an appropriate flexible filler material or gasket. No repairs were made, the cracks had grown slightly, and leaks had increased
at the time of an informal site inspection and visit we made again in June 2007, as shown in the photographs below.
Here are some factors which determine the extent of thermal expansion damage to a brick wall or structure
Proper installation of thermal expansion joints is the critical design factor to avoid thermal expansion damage to brick.
Selection and application of connectors between the brick veneer and the structure is an important factor - some connectors
permit more movement between the brick veneer and the structure. However even if a large brick veneer wall is properly fastened,
if lacks expansion joints damage is likely, especially on the sun-exposed walls
Sun exposure: simply walking around a large structure such as the building complex shown in these photographs, it becomes
quite apparent that thermal expansion damage occurs worst on long brick walls which are facing South and/or those which receive
the most sun exposure.
Means of brick veneer attachment: A second factor in
the probability of damage to a brick veneer wall is the means of attachment of the veneer to the building structure. Brick veneer walls
were traditionally secured to the underlying wood or masonry structure using corrugated steel strips which were fastened at one end
to the structure and at the other end laid in the brick veneer wall at mortar joints.
These connectors permit some vertical
movement between the structures but resists lateral movement. Some newer brick veneer connectors are designed to permit
horizontal as well as some vertical movement differences between the brick veneer wall and the structure. And of course, where
proper expansion joints are provided in the expanse of a brick wall and at windows and doors which penetrate that wall, we
should not see thermal expansion damage to the bricks nor to the structure.
Brick veneer bottom support: on some residential properties we've found loose brick veneer walls that lacked
adequate support to carry their weight.
Typical brick veneer support on a residential building uses either a steel angle
iron fastened to the foundation wall to carry the bricks from their first course, or if the brick veneer was in the
original plans for the building the architect or builder may have specified that the building foundation wall project
approximately 4" (one brick width) out from the building structural wall to carry the load of the bricks.
Combined effects of weather & thermal cracking may increase cracking and movement in a brick structure or brick
veneer structure. It's possible that the wall-corner cracks in the photograph at the top of this page were aggravated
by leaks at the roof or roof parapet since this building is located in a freezing climate.
Distinguishing between brick thermal cracking and frost cracking: How can we distinguish between
brick cracking due to roof or parapet wall leaks and brick cracking due to thermal movement: a leak and frost related crack
on a masonry building tends to be horizontal near the top of the building wall at about the location of the roof surface
behind the parapet wall, or just below that point - describing where water is entering the structure.
in the same brick wall will generate stair-step cracks or vertical cracks near the wall ends (or building corners) and will be independent of high-on-wall
horizontal cracks that map the surface of the roof itself.
Brick veneer vs. structural brick: OPINION: we suspect that at least in some cases, a brick veneer wall might suffer worse damage from thermal expansion than a brick structural wall,
based on the hypothesis that a
brick veneer wall, being a single brick in thickness, has less thermal mass and so will heat up more quickly across its surface than a
structural brick wall which will be two or more wythes of bricks in thickness, joined by bond courses.
Cracks & Movement in Loose Brick Veneer Walls - Support Issues?
See BRICK VENEER WALL LOOSE, BULGED
for details of bulged cracked brick veneer wall damage caused by inadequate support, frost, or building damage - low-rise residential buildings.
Continue reading at BRICK VENEER WALL LOOSE, BULGED or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see THERMAL EXPANSION of MATERIALS for a table of the coefficient of expansion of common building materials including brick, concrete, mortar, and stone.
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