When does a foundation need to be dug out?
Exterior excavation is the step before most outside-the-wall foundation work. Common reasons include replacing or adding drain tile at the footing, applying exterior waterproofing, sealing cracks from the outside, installing wall anchors or bracing, and exposing a wall so an engineer can look at it. On new construction the same idea applies when a wall needs to be reopened before final grade.
The excavation contractor and the foundation contractor are usually two different companies. J1S does the digging, the spoil handling, the backfill, and the grade. The waterproofing or repair itself is done by the specialist you or your builder has hired. Settle that split, in writing, before anyone mobilizes.
How deep and how wide does the dig go?
Deep enough to reach the level the repair needs, which for drain tile and full-wall waterproofing means down to the footing. Wide enough for a person to work safely against the wall. The foundation contractor's scope sets the depth and working width; the excavator should not guess it.
Two limits apply no matter what the scope says. First, the dig must not remove soil from beneath or alongside the footing in a way that undermines it. Second, a trench deep enough to stand in is an excavation under OSHA's excavation rules, so sloping, benching, or protective systems may be required before anyone works at the wall. That affects how much yard gets opened up, and it is a reason a quote can change once the soil is visible.
What is in the way along a house?
More than on an open lot. Gas meters, electric service, water and sewer laterals, downspout drains, air conditioner pads, and sometimes buried propane or oil lines all sit near the wall. A public locate marks the utility-owned portions; private lines on your side of the meter are often not marked at all. The guide to utility locating versus potholing explains the difference.
Where a line crosses the dig close to the house, it is exposed by hand or with hydrovac potholing before a bucket gets near it. Plan for that time in the schedule, especially around the gas meter.
Surface items come out too. Decks, stoops, patios, shrubs, and walkways within the work area usually have to be removed or protected. Decide beforehand who removes them, where they go, and who puts them back.
Where does the dirt go during the repair?
Next to the trench, but not on top of its edge. Spoil piled at the lip adds load and can slide back in. On a narrow side yard in Kirkwood or Webster Groves there may be no room at all, and the soil has to be loaded into trucks and brought back later, or replaced. Include the haul-off and return in the quote if the lot is tight.
Keep the topsoil separate if it can be stripped first. Putting the original topsoil back on top at the end is cheaper than buying new.
How should it be backfilled?
After the repair is inspected and approved by whoever is responsible for it, the excavation is backfilled. Drain tile is typically covered with clean stone such as #57 limestone, with any filter fabric the waterproofing system calls for. The rest goes back in lifts and is compacted, not dumped in one pass. Loose backfill settles, and a low spot along the wall sends roof and surface water straight back to the foundation you just repaired.
If the wall was bowed or cracked, confirm with the repair contractor that its bracing or anchors are complete before backfill starts. Pushing soil against a wall that is still being stabilized can undo the work.
Finish with a grade that falls away from the house on every side. Grading is the step most people remember least and the one that keeps the problem from coming back.
What to send for a quote
Include: the address; which walls or how many linear feet; the depth the repair contractor needs; the repair contractor's name and schedule; photos of each side of the house showing access, meters, decks, and landscaping; whether spoil can stay on site; and any known private lines, such as a sprinkler system or buried downspouts.
J1S handles perimeter and foundation excavation across Jefferson County and St. Louis County, including tight older lots where a mini excavator is the only machine that fits. For new builds rather than existing houses, see basement excavation.