Help: New Interior Wall Footing question
Building a 1 story addition. Framing company starts next week and, alas, all of the concrete guys I’ve called are too too busy for such a small job. So it’s up to me.
Engineer calls for a 16″W, 8″D, 12′ long wall for an interior bearing wall. I’ve cut the concrete, dug the trench, and compacted the soil. What next?
Here’s where I’m unsure. Engineer calls for 2 – #4 rebar (4 in total) on both top and bottom but didn’t give a cross section detail on the spacing. And he’s on vacation till Friday but I’d really like to get the inspector in asap.
How far should the rebar be set apart horizontally? Vertically? And am I correct in reading that the rebar needs to be 3″ from the outside edge of the concrete?
Replies
I'd place them 4" in from the outside edges, 8" apart, and 2-3" from the top and bottom, 3-4" apart.
If the engineer doesn't say, it probably doesn't matter. Code calls for rebar to be at least 3" away from exposure to dirt, and at least 1 1/2" exposure to air. The bottom rebar should be as deep as possible, since that is theoretically the tension side of the footing and rebar is what gives the footing tensile strength. I would put the rebar as far apart as possible given the above rules.
I've never had an inspector comment about rebar spacing. They have pointed out places that had inadequate cover or where chairs or dobies were required.
Well, I guess my engineer checked his email and had someone else get back to me on this. Wish that solved the issue, but it just raised more questions on my part.
THe new detail they sent back to me now calls for a 12" footing with 2 layers of rebar. Indicates a minimum distance of 4" between layers and min. 3" from exposure. Interesting since the original engineering spec called for an 8" deep footing.
Discussed it with my architect and we both agreed to push it back to the engineers for clarification. He thinks the second engineer may have made some assumptions..like perhaps it was an exposed to weather footer (it's not, it's inside the house), or perhaps they thought it's bearing load for the floor AND the roof (it's not).
Not to mention, it just seems like overkill. THis is a footing that holds a bearing wall for part of the floor so that a stairwell can go in perpindicular to joists. Seems kind of silly to require a 12x16 footer with 2 layers of rebar when the rest of the house is sitting on 8 x 15 footers without a lick of steel in them (built 1949).
So we'll see. Wouldn't be that big of a deal except for the time factor.