Sagging Garage Door Steel Lintel Beams
By James A. "Buck" Durham, P.E. Structural Engineer - Durham and Wehrman Engineering,
Phone 256-353-0504.
Perhaps the most common brick veneer cracks in residential construction, other than those cracks
associated with differential foundation settlements, are the ones that form above double-wide, garage door
openings. This is my personal observation (based on more than 13 years of residential inspection
experience) and may not be an accurate or factual statement. Nevertheless, it is my opinion/contention that
crack formations in brick veneer above/beside double-wide garage door openings (in the
Huntsville-metropolitan area) are the rule rather than the exception. I've seen thousands of them!
In order to understand the causes of these cracks, one needs to understand the way in which brick veneer
is constructed above such wide openings. In most cases, the brick veneer located directly above the
opening is supported by a structural steel angle (beam) which in turn rests on the side wall sections of
brick veneer (abutting each side of the door opening). These steel angles are commonly called "lintels or
steel lintels" and generally have an outstanding leg which measures about 2-1/2 or 3-1/2 inches wide. Note
that this width conforms to the typical brick masonry units which are used in residential construction; i.e.
they range from 2-1/2 to 3-1/3 inches wide.
The general construction procedure is to lay-up the brick veneer, along each side of the garage door
opening, until both sides reach the tops of the door jambs. At this point, the brick masons stop laying brick
and the newly-laid brick veneer wall is allowed to harden or cure. After a day or two, a steel angle beam or
"lintel" is laid across the top of the garage door opening the ends of the beam resting directly on the two
brick veneer walls which directly abut the sides of the garage door frame. Once the lintel beam is in place,
the masons continue laying the brick veneer, up and over the steel lintel, eventually embedding the lintel
and hiding it from view.
The size (thickness and cross-sectional dimensions) of steel angle needed to span across the door
opening and adequately support the brick above is based on the weight of the brick above the opening. In
other words, the taller the brick veneer wall above the opening, the more the brick weight. For very tall
heights of brick veneer, however, which exceed the height of an imaginary equilateral triangular who's
apex is created or formed by two sides oriented 45 degrees to the base (lintel), the total weight applied to
the lintel is assumed to be the weight of the brick veneer located inside this triangle. The brick overlying
and/or outside this triangle is assumed to arch or span across/over the opening. For a 16 foot wide opening,
the apex of an equilateral triangle is 8 feet tall!
A normal rule of thumb for determining the weight of brick veneer is to assume that it weighs about 30
pounds per square foot of "face area". Hence, a one foot wide strip of brick veneer wall, eight feet tall,
weighs about 240 pounds. As such, an 8-foot tall brick veneer wall exerts 240 pounds per linear (lineal) foot
on the supporting foundation/footing/lintel/etc. Fortunately, in most residential cases, the height of brick
veneer above the garage door (steel lintel) is usually only about two to three feet tall. In these cases, the
weight of brick supported by the lintel is equal to a uniform load of roughly 60 to 90 pounds per linear foot
(30 psf x2 ft or 30psf x3ft).
In spite of this apparently small weight, however, I can tell you that there are no readily available steel angle
sections (that a local builder can purchase from a steel fabricator) that can span 16 to 18 feet, support its
own weight plus that of 2 to 3 feet of brick veneer, and not deflect, twist or bend excessively. And here is
the rub. Excessive deflection is defined as the lesser of 0.3 inches or L/600 inches, where L is equal to the
lintel span in inches. For a 16 foot lintel, L/600 is equal to 16x12/600 which equals 0.32 inches. That's
roughly 1/3 of an inch (between 1/4 and 3/8 of an inch). This rigid deflection limit has been set by the Brick
Industry Association (BIA) -- formerly the Brick Institute of America (refer to their Technical Note #31B). The
Standard Building Code (which governs construction in Alabama) recognizes and references the
recommendations of BIA. The purpose of the deflection limit is to improve/ensure the long term
serviceability of brick. It is not to imply that whenever larger deflections occur in practice, there is some
"implied" major structural problem or concern. The deflection limits simply reflect the fact that brick
veneer is a hard, rigid and "brittle" material which cannot take (endure) very much distortion without
cracking. Hence, to avoid cracking (which leads to more problems, such as leakage), the BIA has placed
rigid deflection limits on any lintel beam used to support brick.
This means that whenever we see steel angles being used to span across wide openings, like double car
(wide) garage doors, they are hopefully bolted or secured to some type of back-up structural member that
helps provide the added strength (rigidity) necessary to prevent excessive deflection/twisting, and
therefore brick veneer cracking. And this "hope" brings me back to the basis of this article....I contend that
if one were to drive throughout Huntsville and the surrounding communities, and measure the deflections of
the steel angle lintels being used to support the weight of brick veneer extending above double-wide garage
door openings, the measured deflections will typically exceed 3/8 of an inch. I further contend that in those
cases where the deflections are about 3/4 of an inch or larger, you'll find brick veneer cracks somewhere
above the lintel. Conversely, in those cases where the deflections are ½ of an inch or less, I bet you won't
find cracks at least cracks due to deflection.
If my predictions prove true, I hope you'll admit that there is a serious problem in our local home building
industry. In other words, excessive deflection would imply that the steel angle lintels are not being
connected to or reinforced by structural back-up units/members. As such, there appears to be a serious
"lack of knowledge" amongst the local home building trades (and obviously the Code enforcement
agencies) regarding the limitations of steel angle lintel beams. Otherwise, there's an ongoing blatant
disregard for proper lintel beam installation in our local residential construction. Please discuss this topic
with your builder friends. Encourage them to contact the Brick Industry Association at (703) 620-0010 and
request a copy of Tech Note 31B.
A conscientious effort has been made by the authors to provide accurate information; however, neither the
authors nor Alabama Residential Inspection Services, LLC will assume any liability for its use. Readers are
advised to perform additional research, seek other professional advice, and to act on the information
provided, herein, very carefully.
Sagging Garage Door Beams
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