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I have three columns to support lvl beams under an addition and have a question about proper rebar layout for each (identical) footing.

All specs are already checked by engineer, but there is one area I'm not clear enough. I'll be doing this myself and the engineer is away. I cannot wait due to the other deliverables on the project.

Each column will be below the frost line, 30". They will be poured 4 square feet by 1 foot high. A cinder block column of 24"x24" will come up from the middle of that footing to about 7-8' to hold a 4 combined lvl beams to support the weight. Number 4 rebars will be used in the footing & will come up with the cinder block.

Please help me on how to layout the rebars, such as spacing, how far from edge, from soil, how to come up to the cinder block, etc... All this will be inspected by the county prior to concrete pouring.

Thank you!

người Sàigòn
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  • Hello, and welcome to Home Improvement. This sounds like a large commercial building, not a "home"; it may be off-topic here. – Daniel Griscom Apr 12 '18 at 01:57
  • It's our house, which was burned/lost in a fire. We're doing most of the rebuild work ourselves, with our own hands. After meeting greedy contractors trying to milk us, we don't have a lot of options left budget wise. Friends help out but we don't know many professional friends in the field, thus trying this first question here. We are practically homeless now, broke, too, until getting this rebuild done. I dig the the holes with my own hands. Down 30 inches by 4feet, the "addition" is actually just the back half of the house to be supported on these three columns. – người Sàigòn Apr 12 '18 at 02:10

1 Answers1

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Keep the rebar 3”” from the bottom of the footing and 3” from the edge of the footing.

I’d install the #4 bars 8” oc each way. (You’re not concerned with flexural bending of the footing, because the column on the footing is so large 24”x24”).

I would run 4 - #4 rebar vertically in the column and install 4” hook (90 degree bend) in each rebar and extend it into the footing 8”. Make sure the vertical bars are about 1” clear from the edges, so concrete can encapsulate the rebar.

For that height of column, I’d use #3 ties at 12” oc. (#3 rebar you can bend by hand.)

I don’t know what you’re supporting (how much load), but that will support about 30 kips at each footing, unless you’re located in a swamp, like me. And the footing will weigh about 7 kips (dead load) each.

Keep all rebar down 3” from the top of the column.

Lee Sam
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  • Thank you very much @Lee Sam. You answer is going to help us get this right. You mentioned to use #4 bars to come up from the footing, then you also mentioned #3 bars. Where do these #3 bars go? Do you mean to start off from the footing with #4 (how long/far up?), Then continue going up with #3 bars? Also, should I put gravel on the bottom soil? It's normal soil & reasonably solid. – người Sàigòn Apr 12 '18 at 10:16
  • All this is to support the back side of a two story wood frame house 11'1/2 by 30' (the back). The front has the old foundation, which continues via two lvl beams along side and one (2 x15' beams meeting at the middle column) across at the back end. The lvls are 4 bolted together for each beam. Each single lvl is 1"3/4x9"1/2. These lvl will butt onto the old foundation on one end, & then extend to these columns. My friend designed this and her engineer friend helped calculate & sign off. It's likely an overkill. – người Sàigòn Apr 12 '18 at 10:31
  • The #3 rebars are just for the “ties”. Ties are “loops” around the vertical steel to keep them from bowing outward. Make them in square shapes that fit around all 4 vertical #4’s in the column. Space them 12” apart vertically. The soil should be “undisturbed”. If there’s loose dirt in the bottom, be sure to “tamp” it down. – Lee Sam Apr 12 '18 at 20:24
  • Got it. I think I've seen how the ties are done via pictures during my search as well. Now it makes more sense with your explanation. On the vertical bars, is there a certain length requirement if two or more pieces are combined to go up or is it more preferable/better to keep it one single bar? Suppose I run the first four vertical bars up from the footing at about 3 cinder block heights, then connect the next one up. Is that all fine or are there guidelines on certain length/heights to be followed? – người Sàigòn Apr 13 '18 at 09:49
  • Lapping is acceptable and usually preferred in order to insure the rebars are located in the corners. Lap bars minimum 30 bar diameters, or 15”. Use wire to tie bars together to make sure rebars don’t move when dumping concrete into masonry cinder block. Also, use concrete with small aggregate, like 3/4” minus. (1 1/2” minus won’t flow around rebar next to side walls.) – Lee Sam Apr 13 '18 at 14:27
  • I feel much better now that you've helped answer practically all the specifics. We hope to rerun home by the end of May. Thanks much to you! – người Sàigòn Apr 14 '18 at 23:46