This section is a collection of frequently asked questions based off of our discussions with building designers over the years. The idea in this section is to answer the question as succinctly as possible. Sometimes there is a link in the answer that jumps to a paper on this website. Otherwise, feel free to reach out for more information.
QUESTION: Are structural brick veneers required to be supported at every floor of multi-story building?
RESPONSE: Per TMS code, section 12.2, there are commonly known prescriptive options for supporting masonry veneers, and other alternative options. See the following article for more information:
SUPPORTING MASONRY VENEERS
QUESTION: What is the preferred reinforcement size to use within masonry walls?
RESPONSE: Reinforcement sizes can vary within masonry walls. Reinforcement can be used as: a) joint reinforcement, b) standard reinforcement bars to resist bending and shear forces according to the TMS 402/602 code. Bars can be #3 to #9 within walls designed with SD, or #3 to #11 within elements designed with ASD. The mason contractors prefer to use reinforcement bars #6 or smaller (based on recent survey), which is also important to take into consideration.
QUESTION: [WE] are currently working on a project that has 34’ wide opening in 12” reinforced CMU wall. The wall is non- N bearing wall and serves as shear wall. The wall is only exposed to internal air pressure. Masonry lintel designed to span the wall opening, and it is consisted of 7 CMU courses bond beam with 2-#10 at bottom (56” deep bond beam). The masonry lintel/wall runs parallel to building expansions joint. Per MSJC 13 – section 5.2.1.2 requires lateral bracing of compression face. I am wondering what a good practice would be to restrain the compression face of the lintel. And how often the brace needs to occur?
RESPONSE: A masonry lintel sounds like a very good design and an excellent choice for the lintel. One suggestion for the lintel would be to consider more, smaller bars such as 4-#8 (2 each in first two courses), or even 6-#6 (2 each in first three courses). Also, I would suggest a lintel be considered fixed to the wall of each side, and therefore reducing the positive moment and having negative moment at each end. The reinforcement then could be reduced for the bottom, and top reinforcement being added. (possible 4-#6 bottom and 2-#4 top as in example below). For the top of lintel compression face bracing, this can be achieved with the top of the wall framing into the roof system on one side of the expansion joint, assuming the lintel is built integrally with the wall above the lintel and there is vertical reinforcing that continues thru the lintel to the top of the wall. The vertical reinforcing can be minimal, but creates the continuity that you are looking for to sufficiently brace the top of the lintel. Also, the lintel should be built integrally with the jamb on each side of the opening, with the jambs also going up to the top of the wall and tied into the roof diaphragm for support.
QUESTION: I work for a structural engineering firm and am researching best practices for installing new openings in masonry walls. Particularly I’m looking into methods for adding reinforced jambs, dealing with existing (or non-existing) control joints, and the most constructible types of lintels. At first glance, I couldn’t find any guidance on the IMI website, but was hoping someone could point me in the right direction either on the website or to some other source.
RESPONSE: You are correct, there is nothing on our website that addresses this. Your question has many different layers and the solution(s) can be specific to your project. However, here are some general comments. We would be happy to visit your office to discuss this more.
To add vertical reinforcement within an existing masonry wall you would need a clear path for the rebar and appropriate space for grout coverage. Depending on the masonry type (brick vs. CMU for example), this may be impractical. The only way to determine if this is to do some destructive investigation. Why do you want to add reinforcement to existing jambs?
First of all, when you say “control joints” this means to us that you are talking about movement joints that pass through concrete-based materials (as opposed to expansion joints in clay brick). Right? The lack of control joints in CMU can be corrected by cutting in new control joints. This is a relatively easy task.
In new construction, the most constructible (cost, speed, availability, practicality) lintels are masonry lintels (either built in place or prefabricate), followed by precast, or hollow prestressed/precast lintel – see images below. Structural brick lintels also work well. The main idea here is that the last possible solution for you should consider would be structural steel lintels. The problem with structural steel are: differential movement, cost, delivery time, and the effort and failure prone task of putting masonry “soaps” over the steel sections.
For longer masonry lintel span, simply use more courses. Easy. The longest masonry lintel we have designed spans 52’-0” (12-courses). A 34’-0” long masonry lintel (7-courses) was just built a couple of weeks ago at an elementary school in Milwaukee.
QUESTION: How far can we span with a masonry lintel?
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QUESTION: How do mason temporarily shor long masonry lintels?
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QUESTION: How do we design bracing for tops of CMU partitions?
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QUESTION: How come it is recommended to locate CMU control joints away from the end of the lintel?
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QUESTION: Our foundation frost wall is 7-courses and partially grouted with (1) #5 @48” o.c. with a bond beam on top. Do we have to fully grout the wall?
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QUESTION: We have a contractor telling us that CMU foundation walls are less money to build than concrete. Is this true for both frost walls and basement walls?
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QUESTION: We would like to use CMU foundation walls to explore saving money. With a 16” cavity wall we need a 16” foundation wall. Do they make 16” CMU? If so, is this preferred by masons? Or, use (2) 8” CMU.
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QUESTION: Do you have any cost and speed numbers for CMU stair towers vs. cast-in-place concrete?
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QUESTION: When resisting lateral forces with CMU stair towers, what do we need to be aware of?
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QUESTION: When CMU is used as infill to a structural steel frame, how do we connect the walls to columns?
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QUESTION: Why are short CMU wall more prone to cracking?
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QUESTION: Some contractors tell us they prefer steel wide flange lintel rather than masonry lintels. Why is this?
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QUESTION: What design assistance to you have for designing CMU without control joints?
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QUESTION: We have been told to detail our expansion joints in clay brick veneer at ½“ wide. Why is this?
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QUESTION: What are the strength difference between normal weight and light weight CMU?
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QUESTION: How tall can we go with loadbearing 6” CMU?
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QUESTION: For a two-story school project, what type of floor system works well for the 2nd floor?
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QUESTION: How long can a loose veneer lintel span?
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QUESTION: How long does it take for CMU to be produced for a job? Is it ever a long-lead item like structural steel?
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QUESTION: Do you have any good detail for how to control moisture and energy with single-wythe walls in northern climates?
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QUESTION: When using masonry lintels and a loose veneer lintel, how can we close off the wall cavity gap at the widow head?
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