The Building Pad Spec: What to Write Down Before Anyone Quotes It

Ask three contractors to quote "a pad for a 30 by 40 house" and you will get three numbers that cannot be compared, because each has quietly decided what a pad is. One is scraping and levelling native ground. One is bringing in 40 yards of base. One has priced compaction testing and the other two have not.

The fix is not more contractors. It is handing every contractor the same one-page specification, so the only thing that varies is the price. This post is that page. It assumes you have read how a pad is built on Cochise County soils; it does not repeat the why, only what to write down.

1. Footprint, plus a margin, as a number

State the structure's outside dimensions, then the pad dimensions. The pad has to carry footing forms, a concrete chute, scaffold, and the grade that falls away from the wall. Pick a margin, write it in feet per side, and give the finished pad size. Leave it out and the cheapest quote has assumed the smallest one.

2. Finished pad elevation above grade

Say how high the finished pad sits above the natural ground around it. Six inches is a common figure and it is not arbitrary: 2024 IRC R401.3 wants the ground around a foundation to fall at least 6 inches in the first 10 feet, and the simplest way to guarantee that is to start 6 inches up. Cochise County's Building Safety page lists the 2024 International Building Code family and the 2023 National Electrical Code as adopted, so that is the edition a permitted build here is checked against.

On a sloping parcel, give the elevation relative to a stated benchmark (a hub, a corner pin, a culvert invert), because "grade" is a different number on each side of the pad.

3. Compaction, in the numbers that make it a spec

"Compacted" on a quote means nothing. The commercial code lists what a compaction specification actually contains. IBC 1803.5.8 says that where foundations bear on more than 12 inches of compacted fill, the geotechnical report must give the site preparation before fill goes down, the fill material, the maximum lift thickness, the minimum in-place dry density as a percentage of maximum dry density, the test methods, and the number and frequency of field tests.

So a pad spec should state:

• Target density as a percentage of maximum dry density, and the test it refers to (ASTM D1557, the modified Proctor, is the one IBC 1804.6 names).
• Maximum lift thickness before each compaction pass. The earlier post describes fill going in at 4 to 6 inches a lift; whatever you write is what gets inspected.
• Moisture conditioning to near optimum before compaction. In a dry year that means adding water, and it is a line item.
• Test frequency: how many density tests per lift, by whom, and that written results come to you.

For scale, IBC 1804.6 lets fill of 12 inches or less skip the geotechnical report only if it reaches 90 percent of maximum dry density and is verified by special inspection; deeper fill needs the report. The residential code is terser: IRC R401.2 puts foundations on undisturbed natural soil or engineered fill, and R506.2.1 caps fill under a slab at 24 inches of clean sand or gravel, or 8 inches of earth, compacted.

4. Positive drainage, stated as a slope

Write the slope away from the structure and the distance it holds for. The code floor is 6 inches of fall in the first 10 feet (5 percent) under IRC R401.3 and IBC 1804.4; both allow 2 percent where the surface within 10 feet is impervious. Write the pad surface fall and its direction, and on a cut pad the interceptor swale on the uphill side and where it discharges.

If the parcel touches a mapped flood zone, say so. IBC 1804.5 bars approval of grading or fill in a flood hazard area unless the fill is placed, compacted and sloped to resist shifting and erosion during a flood, and the county's Floodplain Use Permit is not waived by any opt-out.

5. Imported base or native, and which native

State whether the pad is built from material cut on site, imported aggregate base, or both, and in what thicknesses. Broken caliche compacts hard and is good pad material; topsoil and anything with organics is not. Under a slab, the IRC's R506.2.2 4-inch base is the minimum reference. If a contractor proposes to "use what's there", the spec should say what happens when what is there turns out to be clay or loose sand.

6. What the structure needs

7. Who signs off

Permitted build. The county's Residential Projects page says every required inspection is listed on the permit's inspection record card and a final inspection is required to close the permit. If your plans show engineered fill, the inspector will want the engineer's report and the test results. The spec should say the contractor provides them.

Owner-builder Option 1. Plans are reviewed, but the county's Owner-Builder page says only key inspections are required: mechanical, electrical, plumbing and fire prevention. Nobody from the county looks at the pad. The spec has to require the tests, because the permit does not.

Owner-builder Option 2. No plan review and no building inspections. The county's final visit is, in its own words, for administrative record purposes and not a code compliance inspection. The only person who will ever sign off on your pad is the testing technician you hire. See what the opt-out does and does not waive.

8. Housekeeping that becomes money

• Stripped topsoil: stockpiled where, or hauled.
• Spoils and oversize caliche: left, spread on the driveway, or hauled.
• Staking: who sets the hubs, and off found corners or off a sketch.
• Erosion control on disturbed ground before the monsoon.
• Permits: the county says permits are generally required for grading projects; say who pulls it, or that you have confirmed none is needed.

What we could not confirm

The ICC's viewer does not expose the 2024 IRC and IBC section text to a plain fetch, so the section numbers above were checked against state codes that reprint the same provisions. Read the adopted edition before relying on a figure, and ask Development Services (520-432-9300) which code year your submission falls under. The county's Building Safety page still carries one sentence referring to the 2015 IBC alongside its statement that it enforces the 2024 codes; we take the 2024 statement as current. We found no county page stating a compaction requirement in words; it arrives through the adopted code.

If you have the parcel and a structure in mind, tell us the parcel and the job and a licensed local contractor will call you to quote it, against this spec.