# Crawl Space French Drain in Wilmington, NC > A gravel-bedded perforated line intercepting groundwater at the footing. The right answer where water. What it costs, and when it is the wrong answer. URL: https://910crawlspacepros.com/services/crawl-space-french-drain/ Home / Services / # Crawl Space French Drain Crawl Space French Drain 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 ASTM E1745 reinforced liner • IRC R408.3 closed crawl space • Class I vapor retarder (<0.1 perm) • ICC-ES certified flood vents • Written scope before work starts 910 Crawl Space Pros provides crawl space french drain across Wilmington and the Cape Fear region. A crawl space french drain is a gravel-bedded perforated pipe that intercepts groundwater at or near footing level and carries it to a sump. It is the right answer where water arrives through the soil rather than over the surface. ## What we do on the first visit Determine whether water is arriving at the surface or through the ground, because a french drain solves only the second. Then check footing depth, clearance and the route to a sump location. ## Washed stone, and why fines ruin a drain The pipe is the visible part; the stone around it does most of the work. It must be washed — screened clean of fines — because the fine material in unwashed stone migrates into the perforations and clogs the pipe. A drain built on unwashed aggregate can silt up within a few years and there is no practical way to clean it. Filter fabric wrapping the stone keeps surrounding soil from doing the same thing over a longer period. ## Interior versus exterior An exterior french drain intercepts water before it reaches the foundation and is the more thorough approach, but it means excavating the perimeter of the house. On a crawl space foundation the cost rarely justifies it. An interior drain at the footing collects water that has already reached the foundation and removes it before it surfaces in the crawl space. For the large majority of Cape Fear properties this is the proportionate solution. ## Fall, and what happens without it The pipe has to run at a consistent fall toward the sump. A flat run holds standing water in the pipe, which silts and eventually blocks. On a long perimeter this is the detail that separates a drain that works for twenty years from one that works for three. ## What's included Assessment confirming water arrives through the soil, not over the surface Trench to footing level at a consistent fall Perforated pipe bedded in washed stone Filter fabric to keep soil out of the aggregate Connection to a sealed sump basin Backfill and reinstatement Vapor barrier installed over the finished system Return inspection after the first sustained rain Price my french drain Free quotes within 24 hours. Free on-site assessment first. Website What do you need? Select a service… Crawl Space Encapsulation Crawl Space Insulation Crawl Space Waterproofing Crawl Space Mold Removal Crawl Space Vapor Barrier Installation Crawl Space Dehumidifier Installation Crawl Space Drainage Crawl Space Sump Pump Installation Crawl Space French Drain Crawl Space Cleanup Crawl Space Structural Repair Sagging Floor Repair Crawl Space Door Replacement Flood Vent Installation Not sure — I need someone to look ZIP code Continue Your name Phone What are you seeing? (optional) Back Request my inspection Got it — your request is in. We'll be in touch with a quote. 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 Crawl Space Encapsulation Crawl Space Insulation Crawl Space Waterproofing All services → ## DIY, cheap quote, or done properly Most of the price difference between quotes is not labour — it is which of these steps the quote silently leaves out. 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 french drain 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. , not a heading: this is a CTA, not a section of the document outline. --> Get crawl space french drain priced for your home Free on-site assessment across Wilmington and New Hanover, Brunswick and Pender counties. Call (910) 886-2018 Get a free quote ## Crawl Space French Drain questions How much does a crawl space french drain cost? Typically $1,500–$5,000 depending on the perimeter length and clearance. Low-clearance crawl spaces cost more because the trench is dug lying down. French drain or sump pump — which do I need? Usually both. The drain intercepts and collects the water; the sump and pump remove it. A drain with nowhere to discharge to only relocates the problem. Will a french drain fix a musty smell? Only if the smell is coming from liquid water. If the crawl space is dry but humid, the smell is a vapour and ventilation problem, and the fix is a liner and conditioning rather than drainage. How long does a french drain last? Properly built on washed stone with filter fabric and consistent fall, decades. Built on unwashed aggregate or laid flat, it can silt up within a few years. Related services Crawl Space Encapsulation A sealed liner across the floor, piers and walls, taped and mechanically fastened, with the vents closed and the space dried. It is the full system, not a sheet of plastic laid on dirt. Crawl Space Insulation Wall insulation for a sealed crawl space, or subfloor batts for a vented one. Which is correct depends on whether the space is closed — installing the wrong one traps moisture against wood. Crawl Space Waterproofing Stopping water getting in, before anything gets sealed. Grading, downspout extensions, perimeter drainage and a sump where the water table demands it.