Question of the Day - #117 Too many footnotes g!

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Question of the Day - #117 Too many footnotes g!

Postby RDavidson » Mon Dec 29, 2014 1:10 pm

So one of my staff members comes to me with a question about compressive strength for concrete footings. She reads from the SONAR an explanation for amendments to Table R402.2. It states: “Footnote “g” permits a concrete mixture that is 2500 psi with an approved admixture (chemicals that can be added to concrete to change its moisture permeability), which provides a water- and vapor resistance equivalent to that of 5000 psi concrete. Footnote “g” includes language stating a minimum 3000 psi concrete strength is required when Tables R404.1.1(5), R404.1.1(6), or R404.1.1(7) are applicable regarding cantilevered concrete and masonry foundation walls. The 3,000 psi concrete will require an admixture that provides water and vapor resistance at least equivalent to 5,000 psi concrete. This language is necessary to eliminate possible confusion between 2,500 psi concrete strength with an admixture and the 3,000 psi concrete strength with an admixture required for cantilevered foundations.”

So this very smart staff member reads footnote “g” from MR 1309.0402. It reads: “g. Compressive strength (f’c) of 2,500 psi, with an approved admixture that provides a water and vapor resistance at least equivalent to 5,000 psi concrete.” She says that the SONAR states that footnote “g” makes reference to 3,000 psi concrete and some tables. She just read it out loud and it makes no such reference. Can I explain it?

It is time to call the psychic in the Bahamas. We ask her the question. She peers into her bowl of alphabet soup and the letters magically align and tell her that although what was read in the SONAR is described as explaining section R402, the second reference to footnote “g” is actually a different footnote “g” that is found in Tables R404.1.1(5), R404.1.1(6), and R404.1.1(7) some 25 pages later and in a different code section entirely and not the footnote “g” in R402 which the SONAR is describing. That is why I have a psychic on retainer at all times.

So we page back 25 pages and find the appropriate tables and the mystery footnotes “g”. We first go to Table R404.1.1(5) and read footnote “g” expecting to find some business about 3000 psi concrete. We read footnote “g” as follows: “Provide propped cantilever wall: top of footing shall be 16 inches below the bottom of the concrete floor slab minimum”. We read Tables R404.1.1(6) and (7) and the read the same. They say nothing about 3,000 psi concrete!

Back to the psychic in the Bahamas. She again peers into her bowl of soup, by now getting a bit cold. She says one of the letters floated away and now it says we should look at footnote “f”. I tell her the SONAR clearly references footnote “g”. She makes some voodoo threats and we relent.

We go back to the tables and sure enough there in footnote “f” is the statement “Minimum footing size of 20 inches by 8 inches shall be placed on soil with a bearing capacity of 2,000 psf. Minimum concrete compressive strength of footings shall be 3,000 psi.”

My staff member starts throwing code books at the wall. She asks who the person (she uses a naughty word) is who hides a footing strength requirement in the wrong footnote 25 pages from the rest of the footing strength requirements without at least making some reference to the appropriate hiding place in the table? She says the SONAR references an admixture requirement for the 3,000 psi concrete to make it equivalent to 5,000 psi concrete and asks where the heck (again she uses a naughty word) that is? It isn’t in any of the footnotes. She asks if we need to call this psychic every freakin’ time (again she uses a naughty word) we are trying to find a code requirement? I cower.

She says that the SONAR states explicitly “This language is necessary to eliminate possible confusion between 2,500 psi concrete strength with an admixture and the 3,000 psi concrete strength with an admixture required for cantilevered foundations.” ELIMINATE POSSIBLE CONFUSION! By now there is fire in her eyes. She says that the SONAR is so confusing and so full of errors that not one (insert expletive here) part of it makes any sense.

Then she goes on to say that many of the foundation she sees contain a mix of cantilevered and non-cantilevered foundations. In fact most are that way. She says what (insert expletive again) is going to pour 15 feet of 3000 psi concrete with an undocumented admixture requirement and then pour 30 feet of 5000 psi concrete and then back to 3000 psi concrete? She asks how do you plan check this. She asks how do you inspect it in the field and insure the right concrete goes in the right trench? I suggest my psychic!

Can anyone point out where the code requires the 3000 psi concrete meet the 5000 psi requirement? My psychic ate her soup. Can anyone explain how you think this will shake out in the field? Will you collect batch tickets from the trucks and watch to see which mix goes where? Anyone?
RDavidson
 
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