Always check with your local building inspector to see what is required in your area. Furthermore, you must install footings at least 12” below unsettled soil.
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).
For a flight of up to five steps, the supporting walls can be centred on concrete footing strips. For a longer flight, you need a concrete pad under the whole structure.
Decide how deep you want each tread to be (individual run - typically 10-12 inches). E. Figure the total run (where the stairway will end) - Multiply the individual run (step D) by the number of steps you have (step B).
Depth of Footings
Footings should extend to a minimum depth of 12 inches below previously undisturbed soil. Footings must also extend at least 12 inches below the frost line (the depth to which the ground freezes in winter) or be frost-protected.
Getting the right outdoor stair dimensions is like setting the stage for a safe and welcoming entrance to your home. Outdoor stair dimensions should include a tread depth of 10 to 14 inches and a rise between 4 and 7 inches for safety and comfort.
It states: "d) Foundations stepped on elevation should overlap by twice the height of the step, by the thickness of the foundation, or 300mm whichever is the greater. For trench fill foundations the overlap should be twice the height of the step or 1m whichever is greater."
A footing underneath a set of steps is a foundation made of concrete and rebar. It spreads the vertical loads from the steps. A footing must be installed below the frost depth, in other words, below the maximum depth the ground will freeze in any particular area.
❖ Footings are required to extend below the ground surface a minimum of 12 inches (305 mm). This is considered a minimum depth to protect the footing from movement of the soil caused by freezing and thawing in mild climate areas.
Footings need to be 600mm wide x 1m deep minimum,in some cases depending on ground quality/type,proximity of large trees footings are required to be up to 2m deep.
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).
All foundations shall extend to a depth of at least 50 cm below the natural ground level. The minimum depth of footing on sandy soil is 0.8 - 1 m, for rocky soil, it is 0.05 - 0.5 m and for clayey soil, it is 0.9 - 1.6 m. The minimum depth of foundation for the load-bearing wall is 900 mm.
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).
International Residential Code (IRC)
The IRC stairs code states that, to comply with stairway requirements, the minimum width for residential stairs be no less than 36 inches. The stair riser code is up to 7.75 inches, and can not vary more than 3/8 of an inch.
How is the depth of a stepped footing determined? The depth of each step is calculated based on the bending moment at that section to satisfy compression, using the same reinforcement as the column face, or beam shear requirements, taking the maximum value.
If entry steps are not properly installed with footings, sink-age may/will occur and water can run in between, possibly causing foundation problems.
Step footings are used for construction on uneven terrain and in areas where soil conditions vary significantly.
Footings shall be a minimum of 8 inches by 24 inches (203 mm by 610 mm) for houses two and one-half stories and less. The footings for a three-story building shall be 10 inches by 24 inches (254 mm by 610 mm).
When measuring for where to place your footers, make sure that the holes will be square with your house and that they are are no more than 8-feet apart in either direction. This is a general recommendation to keep your deck as sturdy as possible.
How deep should a stair tread be? A stair tread should be a minimum of 11″ deep for stairs used as a means of egress under the 2018 IBC building code. A stair tread should be a minimum 9.5″ deep for stairs used as equipment access under the OSHA standards for stairways.
Riser Height and Tread Depth (IBC 1011.5)
The step height, or the riser height, must be no less than 4 inches and no greater than 7 inches. The minimum tread depth is 11 inches. If the stairs have nosings, you measure from the leading edge of the nosing to the edge of the next step's nosing.
Ratio between height (rise r) to width (tread t) of the step. This follows the golden rule which is: 2 x r + t = 63 cm. i.e.: 2 times the rise plus the tread equals 63 cm with a maximum variation of ± 1 cm.