In evaluating cost of brick v. cost of CMU given a wall size (4’ tall by 20’ long), is there a simple method to compare the cost for the brick units and cost for CMU units rather than finding each unit individually?
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Hi @areyes that’s a great question.
@heatherrivera or @cat.heard9 do you mind jumping in?
Hi @areyes, I’m a little confused on what you’re asking, but I think I understand the gist of it. The short answer is yes; you can determine cost of a wall without calculating the exact number of bricks or CMU that make up the wall.
Let’s say we have a question asking which is cheaper, a 4’ x 20’ wall made from brick or CMU. CMU would be comprised of one wythe, brick of two. Brick is 30 cents/SF for materials, and $2.40/SF for labor. CMU is $1.20/SF for materials, $4.00/SF for labor.
- calculate the square footage of material required for each wall.
- 1 wythe CMU x (4’ x 20’) = 80 SF
- 2 wythes brick x (4’ x 20’) = 160 SF
- Calculate the approximate cost per square foot of the wall, including labor and materials
- (80 SF CMU x $1.20/SF) + (80 SF CMU x $4.00/SF) = $416.00
- (160 SF brick x $0.30/SF) + (160 SF brick x $2.40/SF) = $432.00
In this example, the CMU wall would be cheaper to build and install. If the question doesn’t give you the cost/SF of the materials, but gives you a unit price, go ahead and calculate the cost/SF.
For CMU:
Typical CMU dimensions are 8" x 16", which is a total of 128 square inches (SI). 12" x 12" = 144 SI. Say the cost of each CMU is 88 cents. To calculate the average cost per square foot, you’ll do: (128 SI / 144 SI) = ($0.88 / x). To solve, cross multiply and divide to find the answer of x = $0.99 / SF.
For brick:
Brick sizes can vary, so be sure to check the question for any identifying information. Standard brick size in the US is 2.25" x 8". Perform the same calculations above to determine the cost of brick / SF.
Does that answer your question?
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Yes, thank you for the information!
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Hi, first time using this Blackspectacles community.
How would I compare the cost between CMU and a fire-rated shaft wall? Having very little experience cost estimating I would assume a fire-rated shaft wall is more sophisticated which would increase the cost of installation.
NCARB doesn’t offer any recommendations on how to prepare for cost estimating. Where would I find material to help me prepare question like these.
Thank you
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Hi @gfilcidor & welcome to the community!
@heatherrivera do you mind helping with this comparison?
Hi @gfilcidor!
Cost estimating is an area I’ve heard many people struggle with in their studies. A great place to start is really with the NCARB ARE Handbook and their example questions in PDD.
NCARB will be giving you the information you need to answer this type of question - the cost of a CMU block or gypsum/stud. Your job is going to have to be to take the cost information given to you and multiply it out by area (linear foot or sf) and compare the two. You’re not going to need to know current market costs for these materials. It’s also worth noting that this is the smallest percentage of the exam.
As for the direct comparison between CMU and a shaft-wall, you’d be surprised that some tested shaft wall assemblies are very straightforward (two layers of gypsum with breakaway clips, for example). USG has some PDF’s online if you want to look into their construction further, but I don’t want to inundate and overwhelm so I’ll leave the links out of this response.
I hope that brings some clarity. Feel free to reach back out if you have more questions or concerns.
Be well,
Heather Rivera, NCARB
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