Footing Layout and Inspection Readiness

Purpose

A deck footing is accepted on three measurements that have nothing to do with each other: how deep it bears, how much area it bears on, and whether it is where the layout says. All three are visible for about one hour, between the hole being clean and the concrete going in. After the pour, none of them can be checked without a shovel and an argument.

This procedure exists so those three numbers get measured, written down and witnessed while the hole is open, and so nobody pours ahead of the inspection hold point. It prevents the event every deck builder has lived once: a heaved post two winters later, a homeowner asking how deep it went, and nobody able to answer.

Scope

Covers layout, excavation, bearing verification, forming, the open-hole inspection and the pour for cast-in-place deck footings under the IRC, up to and including the post base being set in green concrete.

Does not cover locating buried utilities, which the underground utility locate SOP owns and which gates step 3 here. Does not cover helical piers, driven piles or precast pier blocks; those follow their manufacturer's installation instructions and the evaluation report the AHJ accepted. Does not cover post or beam work above the base, which the post and beam framing standard owns.

Roles and responsibilities

Procedure

1. Reconcile the plan against the site before anything is marked. Confirm footing count, each footing's diameter, the design depth, and the soil bearing value the sizes were derived from. Acceptance: every footing on the plan has a size, a depth and a stated bearing value, and the local frost depth from the building department matches or is shallower than the plan depth. Wrong looks like a plan with footing sizes and no bearing value, which means nobody knows which row of the table they came from. Stop rule: no bearing value, no dig; send it back to the designer. No hazard here, which is why it is the cheapest step to skip and the most expensive skip on the list.

2. Confirm the permit hold points and setbacks. Read the permit for required inspections and the setback dimensions to property lines and easements. Acceptance: the open-hole inspection is on the card, the notice requirement is known in working days, and every footing sits inside the setback by measurement from a surveyed reference, not from a fence. Wrong looks like a fence used as a lot line. Stop rule: a footing inside the setback tolerance stops the job for a survey, because the alternative is breaking out cured concrete by hand.

3. Clear the dig through the utility locate SOP. Complete the underground utility locate SOP and carry its ticket number forward. Acceptance: a valid unexpired one-call ticket, marks present on the ground, tolerance zone honored at every hole. Wrong looks like marks washed off or a ticket past its life. Stop rule: no valid ticket, no auger. Hazard: this is where a deck crew hits a gas service, so any hole inside the tolerance zone of a mark is opened by hand or vacuum excavation, never by auger. If a line is struck or you smell gas, everyone leaves on foot and upwind at once, nothing is started or shut off, no phone or truck is operated in the area, nobody tries to plug or crimp the line, and 911 and the utility are called from a distance. On a struck electrical service nobody touches the tool, the spoil, or anyone in contact with them, and the utility is called.

4. Set the layout and square it. Build batter boards clear of the hole locations, string the deck perimeter and the beam line, and check square by measuring both diagonals of the rectangle. Acceptance: the two diagonals agree within 1/4 inch, and each footing center is marked to plan dimension from the ledger face. Wrong looks like a 3-4-5 check at one corner standing in for the diagonals, which can be square at that corner and out of square overall. Stop rule: diagonals out by more than 1/4 inch get re-strung before anything is dug, since a footing dug off layout cannot be moved after the pour. Hazard: string lines at shin height are a trip hazard for everyone else on site, so flag them.

5. Dig to bearing, not to a number on the auger. Excavate each hole to the design depth, which must be below the local frost line and, per IRC R403.1.4.1, not less than 12 inches below the undisturbed ground surface. Acceptance: the depth reads at or below plan from the finished grade with a tape and a straightedge across the hole, and the bottom is undisturbed native soil, cleaned of loose spoil. Wrong looks like a hole bottomed on fill, on a soft lens, or on 3 inches of augered crumb the operator never cleaned out. Stop rule: soil that changes character with depth, water standing in the hole, or refusal on rock stops that hole and goes to the designer before forming. Hazard: never reach into an open footing hole past shoulder depth and never let anyone stand in one; open holes get covered or barricaded at every break and at the end of every day.

6. Verify the bearing area against the load, not against the auger you own. Confirm the installed diameter delivers the bearing area the design requires for its tributary load. Where your jurisdiction uses IRC Table R507.3.1, the table row for the tributary area and the soil bearing value governs; the hand check below is how you catch a row read wrong. Acceptance: measured hole diameter at the bottom meets or exceeds plan diameter, verified with a folding rule across the bore. Wrong looks like a 16 inch hole where the plan says 18 because that is the bit that was on the truck. Stop rule: an undersized hole is re-augered to the plan diameter or bell-bottomed if the design allows; it is never poured with a note to widen the pad later. Hazard: augering a second pass in a hole with spoil piled at the rim buries the operator's feet, so clear spoil back 2 feet from every rim first.

7. Set forms and hold elevation. Place the form tube, plumb it in two planes, brace it, and mark the pour line at the design top of footing. Acceptance: plumb on a 4 foot level in two directions 90 degrees apart, and the pour line set from the same benchmark used for every other footing on the job. Wrong looks like each footing shot from its own local grade, which puts the beam out of level before a post is cut. Stop rule: a tube that will not hold plumb under bracing gets re-set; do not plan to correct at the post. Hazard: cutting form tube with a circular saw throws paper dust and kicks, so cut on the ground with the tube blocked, never across a knee.

8. Call the inspection and hold the pour. Request the open-hole inspection with the notice your jurisdiction requires, and do not place concrete until it is signed. Acceptance: a written or electronic approval naming the address, the date and the inspector. Wrong looks like a verbal approval nobody wrote down. Stop rule: pouring ahead of the inspection is a stop-work risk and, in many jurisdictions, an order to expose the footings; if the inspector cannot make the window, the holes get covered and the crew moves to another task. Hazard: holes left open overnight for an inspection are the largest fall and animal hazard on the site, so cover each with staked plywood rated to take a step, marked and weighted.

9. Place, consolidate and set the base. Place concrete continuously into each hole, rod or vibrate to remove voids, screed the top and set the post base or anchor bolt into the wet concrete to the layout string before initial set. Acceptance: the base is plumb, at layout, at the correct height, and re-checked after the concrete has stiffened but before it is hard, since a base set once and never re-checked drifts. Wrong looks like a base pressed in at the end of the day and found rotated the next morning. Stop rule: a base out of position after set is chipped out and re-anchored with an approved post-installed anchor, never shimmed sideways. Hazard: wet concrete is strongly alkaline and burns skin under kneepads and inside boots without pain warning, so wear waterproof gloves and boots, tape sleeve cuffs, and rinse any contact immediately; mixing bagged concrete releases respirable crystalline silica, so mix downwind with the dust-control method your silica plan under 29 CFR 1926.1153 names.

10. Record and release to framing. Write the footing record while the pour is fresh, then hold framing until the concrete reaches the strength the mix or the plan requires. Acceptance: every field in the record below is filled and the cure hold carries a release time. Wrong looks like posts set on green concrete the same afternoon. Stop rule: no record, no release; nobody hands the deck to the framing crew on memory.

The record this produces

One footing record per job, one row per footing, filed against the job before the crew leaves site:

• Footing mark, plan diameter, measured diameter, plan depth, measured depth from finished grade.
• Soil description at the bottom of the hole in plain words, and whether it was native undisturbed or fill.
• The one-call ticket number carried over from step 3, and the step 8 inspection date, inspector and approval reference.
• Concrete type or mix, placement date and time, and the cure release time from step 10.
• A photo per hole with a tape reading depth, and a photo of the set base at layout.

The inspector reads it at the framing inspection. The office reads it when a warranty call comes in. The estimator reads it the next time the shop bids in that soil, because "clay to 42 inches, water in two holes" is worth more on the next bid than anything in the proposal.

One run, including the stop that fired

Job: 16 foot by 12 foot attached deck. Joists span 12 feet clear from ledger to a beam under the outer edge, no cantilever. Plan design load is 40 psf live plus the 10 psf dead load our plans carry for pressure-treated framing with a composite surface. Beam posts at 0, 8 and 16 feet. Plan bearing value is 1500 psf, the presumptive value IRC Table R401.4.1 gives for clay and silty clay, which matches the soil report language.

The interior post is the one that sizes the job. It carries 8 feet of beam length, 4 feet each side, and the beam picks up half the 12 foot joist span, so 6 feet of tributary width. That is 8 times 6, or 48 square feet, at 50 psf combined, which is 2400 pounds. At 1500 psf, that needs 2400 divided by 1500, or 1.60 square feet of bearing, which is 230 square inches. The plan called an 18 inch diameter footing: 9 inch radius, 254 square inches, or 1.77 square feet. That clears.

At step 6 the crew measured 16 inches at the bottom of all three holes, because the 16 inch auger bit was the one on the trailer. A 16 inch hole is 201 square inches, or 1.40 square feet, which is 13 percent short of the 1.60 required and well short of the plan. The end footings would have passed on load at that diameter, since each carries only 4 feet of beam length, or 24 square feet and 1200 pounds, needing 0.80 square feet. The interior one would not. The stop rule fired: rather than pour two and argue one, the lead had all three re-augered to 18 inches the same afternoon, which cost about two hours and kept one footing record consistent across the job.

Step 8 held overnight on one working day of notice. The three holes were covered with staked and weighted plywood, and the inspector signed the next morning, noting a measured depth of 42 inches against a local frost depth of 36. Step 9 placed the same day; step 10 released framing the following morning.

References

• IRC Section R403.1.4.1, footing depth below frost line and not less than 12 inches below undisturbed ground surface
• IRC Section R507.3 and Table R507.3.1, deck footing size by tributary area and soil bearing value, in the edition your jurisdiction has adopted
• IRC Table R401.4.1, presumptive load-bearing values of foundation materials
• OSHA 29 CFR 1926.1153, respirable crystalline silica in construction, which governs the mixing control in step 9
• See related: the underground utility locate SOP, which gates step 3, and the post and beam framing standard, which picks up at the post base