Crawl space water is the one problem on this site where the most expensive solution is frequently the wrong first move. Before pricing an interior drainage system, it is worth understanding what is actually happening, because the fix for the common case costs a few hundred dollars and the fix for the uncommon case costs several thousand.
Where Triangle crawl space water actually comes from
The Piedmont sits on Cecil-series red clay. Undisturbed, it drains reasonably. A graded house lot is not undisturbed: the topsoil is stripped, the clay underneath is compacted by machinery, and then roofs, driveways and patios concentrate rainfall onto a much smaller area than it used to fall on. The result is that a great deal of water arrives at the foundation quickly and then has nowhere to go quickly.
That is why the majority of wet crawl spaces here are fed from the surface rather than from below. The tell is timing: water that appears during or shortly after heavy rain and drains away over a few days is surface water. Ground that stays wet between storms, in dry weeks, is a different problem.
The work that usually comes first, and what it costs
None of the following is crawl space work, and none of it is priced on this site, because it is landscaping and roofing rather than foundation work. It is listed because it is routinely the actual answer:
- Extending downspouts. Getting roof water several feet from the foundation instead of discharging it at the corner of the house. Materials cost is trivial; the labor is an afternoon.
- Correcting grade. Building the ground back up so it falls away from the foundation rather than toward it. Usually a few loads of soil and a day’s work.
- Clearing the vents. Mulch, shrubs and raised flowerbeds that have crept above the vent line let surface water in directly.
A contractor who looks at a wet crawl space and tells you to fix your gutters before spending anything with them is giving you the most valuable advice in this article.
Interior drainage
When surface water has been dealt with and the space still takes on water, interior drainage is the answer. A trench is cut around the affected perimeter, perforated pipe is laid in gravel, and it is run to a sump basin or, where the ground falls away enough, to daylight.
It is priced by the foot because that is what varies. The published range is $40 to $100 per linear foot for interior installation, which is the most expensive kind of drain per foot - everything is dug, carried and installed lying down in a confined space. A 50-foot run comes out around $2,000 to $5,000 and a 100-foot run around $4,000 to $10,000.
The number that matters in a quote is therefore the run length, and it is the number worth pushing on. Water rarely enters evenly around a foundation. If one wall is where it comes in, draining that wall may do the job. A quote specifying the full perimeter should be able to say why.
The sump pump
Where the drain cannot run to daylight, it runs to a basin with a pump. National figures put sump pump installation between $500 and $4,000 with an average around $1,400, and a crawl space sits at the cheap end of that range for a straightforward reason: the basin is dug into dirt rather than cut through a concrete slab.
What is worth asking about is everything around the pump rather than the pump itself:
- Where the discharge goes. A line that dumps at the foundation returns the water you just paid to remove. It needs to get well away from the house and not into a neighbor’s yard.
- Freeze protection. The Triangle gets enough hard freezes for a discharge line to ice up, at which point the pump runs against a blocked pipe.
- What happens in a power cut. Storms cause both the water and the outage. A battery backup is a meaningful addition; it is also an extra cost that belongs in the quote rather than in a conversation afterwards.
- Whether anything tells you it failed. A pump in a crawl space fails silently. An alarm is inexpensive.
What these figures do and do not tell you
The per-foot and per-pump ranges below are published guide figures, and the drainage ones are national rather than North Carolina-specific - there is no published Triangle rate for interior perimeter drain. They are useful for telling whether a quote is roughly right. They are not a quote, and they cannot be added together into a project price: none of them includes mobilization, hauling spoil out through an access hatch, or the contractor’s overhead.
The only way to price this work properly is for somebody to get under the house during or after rain and see where the water is actually coming in.
Once the water is handled, sealing the space is separate work at its own price; the crawl space encapsulation cost page sets out the published figures for it.
Prices on this page are general ranges gathered from published sources, not a quote. What a job actually costs depends on the specifics of the job and who does the work. Only a quote from a qualified contractor who has seen the job is a real price.
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