Steel Detail for Concrete Footing
I am building fire escape. There is no steel detail included in the plans. We have no clue what the description is calling for.
It reads 18"W x18"D x 8' conc. footing
W7 3-5s CONT.
T. B. W7 S SHORT BARS @ 12" O.C.
can you please explain?Answer:
Sorry that I get to your question late
This 18"W x18"D x 8' conc. footing – means the footing is 18 inches wide by 18 inches deep by 8 feet long. The W7 is probably means w/ (short for with) an expression normally used by architects to mean with.
The expression should read like this: Footing is 18 inches wide by 18 inches deep by 8 feet long reinforced with 3#5 x con’t which means it has 3 – 5/8 inch diameter rebar 8 feet long which is the continuous part of the footing.
The last line: T. B. W7 S SHORT BARS @ 12" O.C.
T.B. mean top and bottom reinforcements in the short direction which is 18 inches long. I think the S is a typo it should be 5 which is the size #5 or 5/8” diameter of the crosswise reinforcement to be spaced at 12 inches on center (center to center)
I think the plan calls for footing reinforcements to be 3#5 top and bottom for a total of 6 lengthwise. The crosswise reinforcements should be #5 spaced at 12 inches center to center top and bottom. In other words, this footing reinforcements has one layer of rebar at the top located about 3 inches from top of footing and another at the bottom located about 3 inches from the ground.
I agree with your assessment, this is very unclear information and it should had been discussed with engineer prior to construction.
This type of concrete footing call out is typically found on electrical, mechanical, and sometimes architectural drawings footing callout is unclear.