The foundation dig sets the depth, the footprint and the working room for everything the concrete crew does next. We dig footings and foundation walls to the plans and the stakes, keep the bottom clean, and put the spoil where it won't be in anyone's way.
Foundation Excavation in Boise, Dug to the Plans
A foundation hole looks simple from the street. Up close, every inch matters. Too shallow and the footing sits in frost. Too deep and someone has to fill the extra back with concrete or compacted rock. Too tight and the form crew can't get their panels in.
We dig foundations for new homes, additions, garages and shops in Boise, Meridian, Eagle, Nampa, Kuna and Star, working out of Caldwell. This page is about the dig itself. For the full sequence on a new lot, from clearing to rough grade, see site excavation.
Starting From the Plans and the Stakes
Before the bucket goes in, we go through the foundation plan with you or your builder. We're looking for the footing width, the top-of-footing elevation, any step-downs where the grade changes, and pads for posts or columns inside the footprint.
The surveyor or builder sets the corner stakes and a benchmark elevation. Corner stakes get dug out, so we set offset stakes a few feet back to keep the layout. From there we check depth against the benchmark as we go, not by eye. If the lot still needs topsoil stripped or cut to pad height, that comes first. See site cuts for new homes.
How Deep the Dig Goes
Boise uses 24 inches as the frost depth for footings. That means the bottom of the footing has to sit at least 24 inches below finished grade, so frost can't heave it in January. On a crawlspace home, the dig often goes deeper than that so there's crawl height under the floor framing. A full basement goes much deeper, and that's its own job, covered on our basement excavation page.
The plans set the number. Where the lot slopes, the footing usually steps down in sections so it stays below frost along the whole perimeter. Each step gets dug level, with a clean drop between sections, so the form crew isn't guessing where one ends and the next begins. We mark the step locations off the plans before we dig and check each one against the benchmark.
Over-Dig: Room to Work
We don't dig the hole to the exact size of the footing. We dig it wider. That over-dig gives the form crew room to set and brace forms, lets the waterproofing go on later, and leaves space for a footing drain if the plans call for one.
How much extra depends on the depth and the soil. On deeper cuts, OSHA requires sloping, benching or shoring once a trench or wall gets to 5 feet and people will be working at the bottom. Sandy river soil and decomposed granite in the foothills need flatter walls than tight clay or caliche.
A Clean, Undisturbed Bottom
Footings belong on undisturbed soil or on fill that's been compacted and tested. Loose dirt left in the bottom of the trench will settle. We finish the bottom with a smooth bucket and clean up the last bit by hand where needed.
If we find a soft spot, an old buried stump hole or a pocket of fill, we stop and talk with you. Usually the fix is to dig it out and replace it with compacted gravel or let the engineer decide. Most building departments inspect the footing excavation before concrete goes in, and a clean bottom is what they want to see.
Water is the other thing that ruins a clean bottom. A summer storm or a neighbor's irrigation can fill a fresh trench overnight, and soaked soil at the bottom has to dry out or be dug out before concrete. Near the Boise River in Eagle and Garden City, groundwater can seep in on its own during irrigation season. We try to time the dig so the form crew follows close behind, which leaves less time for weather to undo the work.
Spoil Handling
A house foundation turns up a lot of dirt, and with the over-dig it's more than most people expect. Where it goes matters almost as much as how it comes out. A pile in the wrong spot can block the concrete truck, bury a stake or slide back into the hole after a rain, so we agree on pile locations with you or your builder before we start.
- Topsoil gets stripped and piled separately so it can go back on for landscaping.
- Subsoil gets stockpiled on the lot for backfilling once the walls are in.
- Piles stay back from the edge so they don't load the walls of the hole or roll back in.
- Access stays open for concrete trucks and the pump.
- Extra material that won't be needed gets hauled off. See dirt hauling.
What Changes the Price
Depth and footprint drive most of the cost. Caliche in Meridian and Kuna, basalt in parts of Southeast Boise, and cobble near the river all slow the dig. Tight infill lots in older Boise neighborhoods take more care and smaller passes. Hauling spoil off site adds trucking. We look at the plans and the lot before we bid.
What Happens After the Dig
Once the hole is done, the form crew sets the footing forms and the building department inspects before the pour. If the inspector wants a spot dug deeper or cleaned up, we can come back and take care of it. After the footings and walls are poured and the walls pass inspection, the stockpiled subsoil goes back in as backfill, placed in layers around the foundation. Then the lot gets rough graded so water runs away from the house.
Why Builders and Homeowners Call Us
We're an Idaho registered contractor (RCE-65836) based in Caldwell, with a 5.0 rating on Google. Reviews describe us as "professional, efficient and highly skilled" and say we "arrive on time." On a foundation, that means the hole is ready when the form crew shows up. Call (208) 697-2429 or request a free estimate.
