Masonry wall reinforcement detail
Masonry wall reinforcement detail
(OP)
I have seen some engineers call for a reinforced bond beam with 2- #4 or #5 bars continuous as the first course of CMU atop a continuous concrete spread footing which also contains continuous reinforcement. I have seen other engineers not require a bond beam at this location. My question is, whether there is some prescriptive requirement or logical design reason for this reinforcement? Under the IBC code, would a seisic design category C or D have any effect on the answer? I have seen NCMA (National Concrete Masonry Association) details that depict this reinforcement and others that do not, without giving any mention of its reqirement, that I have found.






RE: Masonry wall reinforcement detail
RE: Masonry wall reinforcement detail
The use of a bond beam is just good construction to provide continuity, good load distribution and added strength during and after construction.
In many cases, it is not required by code, but that does not mean the omission of it is good. - "If you go by the code, you are not wrong, but you may not be right".
I would not design or build a wall without a bond beam at the top.
RE: Masonry wall reinforcement detail
RE: Masonry wall reinforcement detail
But if you design the wall to resist moment at the bottom then I would put reinforced spread footing with enough dowels into the cmu wall. I dont think the bottom 2 rebars would be necessary anymore since the footing act as one with the cmu.
I hope I am making any sense.
Never, but never question engineer's judgement
RE: Masonry wall reinforcement detail
RE: Masonry wall reinforcement detail
I admit that I automatically assumed it was the top course instead of the unusual situation in the first course.
Is this a common basement or a more substantial structure with unique loadings?
If it is a common basement, reinforcement is not even required in most areas and applications. The footing is just a means to provide a level area to build a basement under the prescriptive design requirements of the IRC or the empirical methods of ACI 530. - In these cases, as an engineer, I feel a detailed design usually not required. For a basement, in many cases a bottom bond beam or even full mortar bedding distrupts many moisture control methods.
Some engineers may prefer the approach you mentioned for some reason.
If there is any vertical reinforcement, a reinforced footing with appropriate dowels for the reinforcement would be the preferred method. Adding a bond beam on top of this would serve no purpose and only complicates the constructability and reliability of the wall.
Dick
RE: Masonry wall reinforcement detail
RE: Masonry wall reinforcement detail
RE: Masonry wall reinforcement detail
RE: Masonry wall reinforcement detail
Mike McCann
McCann Engineering
RE: Masonry wall reinforcement detail
You also have to lay the bond beam course and then pull the mason's off the job or send them to another part of the job if it's big enough, until it gets a partial inspection and poured. This in particular is a lot of hassle for a couple of bars that don't add any real benefit imo.