How much does crawl space drainage cost?

Typically $1,500–$5,000, driven by the length of the perimeter run and how accessible the footing is. Low clearance raises it because everything is done lying down. This is the single largest variable in most Wilmington encapsulation quotes.

Do I need drainage if my crawl space is only damp?

Damp without standing water or a high-water mark is usually a vapour problem, not a liquid water problem, and a liner plus dehumidification handles it. Drainage is for liquid water arrival. The assessment distinguishes the two.

How long does a sump pump last?

Typically seven to ten years in crawl space service. It is a mechanical device with a float and a motor, and it will eventually fail — which is why the basin should be accessible rather than sealed under a liner with no way in.

Can drainage go in after the crawl space is encapsulated?

Yes, but it costs considerably more, because the liner has to be lifted along the whole perimeter and re-terminated afterwards. This is the main reason the order matters.

Do you install sump pumps in Ogden, Porters Neck and Wrightsboro?

Yes — those communities sit inside our normal New Hanover County coverage along with Murraysville and Kirkland, and the high water table on that side of Wilmington makes sump work common there. The crawl space sump pump installation page covers the sealed-basin spec; installed with a perimeter drain it is part of the $1,500–$5,000 drainage scope.

Crawl Space Drainage

What the work involves in Wilmington and the Cape Fear region, what it costs, and the situations where it is the wrong thing to buy.

Last updated: 2 August 2026

910 Crawl Space Pros provides crawl space drainage across Wilmington and the Cape Fear region. Crawl space drainage is a system that intercepts water before it reaches the crawl space floor and moves it to a discharge point. In practice that means perimeter drain tile at the footing, a sealed sump basin, a pump and a discharge line — installed before any vapor barrier goes down.

What we do on the first visit

Establish where water arrives and how high it gets. Perimeter inspection for grade and downspouts, interior survey for the high-water mark, and a check of whether the footing is accessible for a drain run.

Drainage before liner, always

This is the sequencing rule that decides whether an encapsulation lasts. A liner installed over a crawl space that still takes water does not stop the water; it covers it. The water is then under an impermeable sheet where it cannot evaporate and cannot be seen.

Retrofitting drainage under a finished encapsulation means lifting the liner, which is most of the cost of installing it in the first place. Where the assessment finds water, drainage is quoted first — even when that makes the quote look worse against a competitor who skipped it.

How a perimeter system is actually built

A trench is cut at the interior perimeter, down to footing level. Perforated pipe is bedded in washed stone — washed matters, because fines migrate into the pipe and clog it — and run at a fall toward the sump location. Filter fabric keeps soil out of the stone.

The sump basin is sealed rather than open, because an open basin in a sealed crawl space is a direct route for soil gas and moisture. The pump is sized to the expected volume with a check valve so discharged water does not run back down the line.

The discharge is the part that gets forgotten

A pump that discharges three feet from the foundation returns the same water to the same place. The line has to carry water genuinely away — well clear of the foundation, to daylight at a lower elevation or to a drainage point that can take it.

In a freeze the line matters too. A discharge that ices at the outlet backs the system up at exactly the moment it is needed.

What's included

High-water-mark survey to establish how high water actually reaches
Interior perimeter trench to footing level
Perforated pipe bedded in washed stone with filter fabric
Sealed sump basin, not an open pit
Pump sized to expected volume, with check valve
Discharge line routed well clear of the foundation
Vapor barrier installed after the system, never before
Return inspection after the first sustained rain

Price my drainage

Free quotes within 24 hours. Free on-site assessment first.

Standards we work to

ASTM E1745 — vapor retarder specification
Class I vapor retarder, below 0.1 perms
IRC R408.3 — unvented crawl space conditioning
NC Residential Code crawl space requirements

Other services

	DIY	Cheapest quote	Done properly
Liner	6 mil builder sheet, laid loose	6–8 mil, taped seams, not fastened to walls	Reinforced 12–20 mil to ASTM E1745, sealed to piers and walls
Groundwater	Not addressed	Sealed over — water ends up under the plastic	Drainage and sump first, liner second
Humidity control	None, or a household dehumidifier on an extension cord	Undersized unit, condensate draining to the soil	Unit sized to cubic footage, pumped to a proper discharge
Vents	Left open, or foam blocks pushed in	Covered, not sealed	Sealed and detailed so the space is genuinely closed
Wood already affected	Bleach from a spray bottle	Surface treated, moisture source left in place	Growth removed, framing treated, dried, then sealed
What it costs	$300 – $900 in materials	$1,500 – $3,000	$4,200 – $14,000
How long it holds	A season or two	Often fails within a few years	Liner life measured in decades when water is handled first

How drainage work runs

01
Assess and measure

Humidity, moisture content in the framing, standing water, clearance and access — photographed throughout.
02
Written scope

Line by line, in the order the work has to happen, with a price against each component.
03
The work

Water handled first where present, then the fix itself, then verification.
04
Verify and hand over

Post-work readings recorded and left with you, along with the photographs.