Rebar, short for reinforcing bar, is a critical component in concrete footing for any structure. It is a steel rod or wire mesh added to concrete to enhance its strength and durability.
You should always put two or three #5 rebar, evenly space, in your concrete footings. It is very cheap insurance to strengthen the concrete footing.
The steel rebar in the concrete IS THE SAFETY MAT for eliminating hazardous step and touch voltages. It MUST be bonded. If the steel rebar is not bonded, you would need to install a copper grounding grid under the workers feet in order to keep them safe.
To estimate the number of rebars for the length, divide the length of the pour by the chosen spacing. Similarly, for the width, divide the width of the pour by the spacing. Multiply the two results to get the total number of rebars required for the grid.
4 bar located 3 to 4 inches (76 to 102 mm) from the bottom of the footing must be provided.
Required Footing Sizes
In most cases, a house should have a minimum footing of 12 inches wide by 12 inches deep, with foundations that are 8 to 10 inches thick. This should be enough to support house weight and resist lateral soil and water pressure.
For every 2 feet of adjustment to the width of the house, add or subtract 2 inches of footing width and 1 inch of footing thickness (but not less than 6 inches thick).
ii) The depth of the foundation should be a minimum of 500 mm. iii) For reinforcement, footing is treated as an inverted slab. As per IS:456-2000, the minimum percentage of reinforcement of steel is 0.12% of the gross sectional area with HYSD bar and 0.15% of the gross area with plain bars of mild steel.
A minimum of 12”inches deep for all footings and the width will be determined by the amount of stories, 12” inches for a single story, 15” inches for a two story and 23” inches for a three story. This is based on a soil bearing capacity of 1500(psf).
Gravel provides drainage, stabilizes the soil, prevents erosion, and helps distribute weight more evenly. Without it, you risk the potential damages listed above. If you're planning a concrete project, don't skip the gravel layer—it's a foundation that ensures your concrete work stands the test of time.
We usually recommend that a minimum of two pieces of #4 rebar be placed vertically in an 8-inch-diameter concrete pier supporting a structure. A larger-diameter pier should have four or more pieces of vertical rebar.
Rebar is recommended for concrete slabs that measure 5 – 6 inches in depth, which is about the depth of slab you'd need if you plan to drive on it or use it to house heavy machinery (like a large RV, for example).
Meanwhile, when constructing columns, piers or walls, a rebar of 8mm or greater must be used, and for foundations and building footings, a rebar of at least 10mm in diameter is the best choice to minimise settling.
Deck pier blocks are used in deck building as an alternative foundation to traditional footings. They are placed directly on the ground, and do not require digging or pouring. They come pre-formed with holes for attaching the posts of a deck, making it easy to install.
Any construction element that is intended to carry a heavy load should always be reinforced, especially foundations, footings, columns and slabs.
The minimum depth of footings below the surface of undisturbed soil, compacted fill material or controlled low strength material (CLSM) shall be 12 inches (305 mm). Where applicable, the requirements of CBC Section 1809.5 shall also be satisfied. The minimum width of footings shall be 12 inches (305 mm).
The footing is reinforced with an orthogonal rebar grid that may have bars of different diameter and spacing in either direction. Bending the rebars ends helps in the proper anchorage of the reinforcement.
Rebars spacing
The minimum spacing between two reinforcement bars should be at least equal to the maximum coarse aggregate dimension plus a margin of 5 mm.
Footing thickness - 8 to 12 inches. Footing depth - varies based on frost line and soil strength (some footings can be shallow, while other must be deep)
Footings are structural supports that are used in addition to a foundation. They help transfer the load's weight from the foundation into the soil. Footers are typically in direct contact with the ground, while the foundation is in contact with the footing.
Each deck support post must be supported by concrete footings. The size of each footing is determined by the tributary load imposed on it. See the diagram below for an explanation of tributary load. Footing must be dug down into undisturbed soil and to a minimum depth of 12-in below the finished grade.
Even the best contractors occasionally have to build on a sloppy footing. Ian Geisler, a noted ICF expert who has worked on hundreds of projects across the continent, says that realistically a perfect footing is anything within ¼” of level. “If it's within ½”, then it's workable,” he writes.