How do Interpret Table 2 in TMS 602-16 in order to get the required net area compressive strength of an individual block for a specified f'm?I have included an article below explaining the increased block strength. It includes a copy of Table 2 so that you can reference it as you read this. The values of f'm are listed in the left most column and are labeled "Net area compressive strength of concrete masonry". Values are given in psi. The right hand two columns give the required Net area strength of the individual unit to achieve the given f'm. The far right column is to be used if Type "N" mortar is used to lay up the wall and the middle column is used if Type M or S mortar is used in the wall. Thus, an individual block with a net area strength of 2000 psi gives you an f'm = 2000 psi. An individual block with a net area strength of 3250 psi gives you an f'm = 2500 psi. And an individual block with a net area strength of 3900 psi gives you an f'm = 2750 psi. Links to additional information:
Update on Increased Design Strength of CMU 1-3-18 with Attachment 1.pdf
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We are bidding a job where the project engineer is requiring a 2500 psi block to meet an f'm of 1500 psi. We know that the new code allows a 2000 psi block to have an f'm of 2000 psi. What can we do?Lets be clear, the project engineering can call for any strength block they desire - as long as it is called out in the project specs that are bid with the job. So if your project specs call for a 2500 psi individual block strength and an f'm of 1500 the 2500 wins and that is what you need to supply to the job.
On the other hand, if the specs ONLY call out for a masonry unit that meets 2000 psi f'm they MUST accept the current code and accept a 2000 psi individual unit strength. Requiring a higher strength unit than is required by the code, and not called out in the bid documents, would constitute a change to the project. During the Masonry Workshop I attended, there was a mention of a website where you could get AutoCad details of for masonry. What was that website? A good source of details is the National Concrete Masonry Association's (NCMA) website. Other websites that offer good information on masonry construction details is the International Masonry Association (IMI) and the Masonry Contractor's Association of America (MCAA). For Clay Masonry you want to visit the Brick Industry Association's (BIA) website. On the NCMA's website the details and the NCMA TEK notes (another great source of info) are housed under the "Solution Center" button. All of these websites are great sources of masonry details and Info. Links to additional information:
https://ncma.org/ https://www.masoncontractors.org/ http://imiweb.org/ http://www.gobrick.com/ A school gymnasium was built with concrete masonry and direct applied stucco. It experienced leakage and so they put a stucco on lath over the direct applied stucco. They are now experiencing more leakage and are wondering what they can do. There are two completely separate issues created by the stucco over lath added to the structure. The first and most important issue is the nature of the fasteners used to attach the stucco on lath to the structure. The fasteners should have been stainless attached through the existing stucco into the masonry substrate. Since the structure is leaking again it can be assumed that the drainage plane between the two coatings is holding water. If the fasteners were not SS then there could be problems with corrosion.
The second issue is the leakage which, if the new stucco on lath has been properly fastened to the masonry substrate, is a matter of completely sealing all cracks and control joints and giving the stucco a few new coats of acrylic paint. Does the backer rod have to be larger or smaller than the joint that is being created? Backer rods are important to prevent 3-point bonding at the crack in the back of a joint. Also, they control the amount of caulking that a joint requires.
For expansion joints the backer rod should be just large enough to fit snugly into the control joint (which should be 3/8" for CMU walls). There should be about 1/2" of depth from the backer rod to the surface of the masonry wall. The backer rod should be snug enough to stay in place during caulking of the joint. What strength do I need on my individual block to attain an f'm=2500 psi? Under the FBC-Building 5th Edition you required an individual block strength of 3750psi to attain an f'm=2500. Under the new 6th Edition Florida Code you only need a strength of 3250 psi. The change is in Table 2 in TMS 602-16. The strength of masonry was increased by about 35% from the TMS 602-11 which was the Masonry Standard referenced in the 5th Ed FBC-Building.
Engineer from Texas writes "If the specs and code noted are not followed, then Florida Building Code section 2109.5.2 governs, which states that bond beams would then be required spaced not more than 48 inches apart. Is this true? Although I don't have access to the plans and specs I can assure you of two things. The first is that there is no section 2109.5.1 in either the 2014 or the 2017 editions of the Florida Building Code. The second thing is that there is no requirement for bond beams at 48" on center in any code pertaining to the State of Florida.
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