A French drain is a gravel-filled trench containing a perforated pipe that intercepts and redirects groundwater and surface runoff away from problem areas such as foundations, patios, and low spots [7][8][5].
Use a shallow landscape or patio French drain for surface diversion and small low spots; use a footing/perimeter drain when the goal is to protect a foundation or under‑slab area, which requires installation at footing level [7][5].
Typical pipe for footing/perimeter drains is 4-inch perforated PVC or equivalent rigid pipe; 4" is commonly listed as typical for footing drains [5][6][3].
Common backfill around drain pipe is free‑draining aggregate (commonly #57 crushed stone or equivalent); footing drains are placed on a bed of clean stone and may require granular backfill adjacent to foundation walls in poorly drained soils [6][5].
Industry guidance recommends a stone bedding under the drain pipe; some references note roughly 2 inches of stone under the pipe as a minimum in some contexts [6][5].
Non‑woven geotextile filter fabric is commonly recommended to wrap pipe and gravel (a "burrito" wrap) to reduce clogging by fines; some how‑to sources recommend an 8‑oz non‑woven fabric for certain installs [8][4].
Prefabricated trench products (mesh/receiver units with an integrated pipe, e.g., NDS "EZ‑Drain") are sold to reduce or eliminate hauling and shoveling gravel and are marketed as faster to install for landscape/yard drains [4].
Manufacturer and industry literature (ADS, NDS) include product‑specific guidance and should be consulted for sizing, fabric specification, and selection for a given installation [3][4].
Shallow landscape or patio French drains commonly use trench depths in the range of about 12–18 inches for yard/patio applications; some sources note 6–12 inches can suffice for surface diversion depending on the use case [7][8].
Footing/perimeter drains intended to protect basements or under‑slab areas must be installed at footing level, which commonly requires trenches 2–4+ feet deep depending on local foundation practice [5][6].
Because local foundation practice and frost depth vary, exact footing depth and trench requirements depend on your foundation and local code; check local guidance before assuming a depth [5][13].
When gravity drainage to daylight is used, a commonly recommended minimum outlet slope is about 1/4 inch per foot (0.25"/ft); some references accept 1/8"/ft for long runs with correct sizing, but steeper slopes perform better and local code or UPC guidance should be checked [5][6].
French drains should outlet to daylight, an approved storm system, or a drywell; connecting to a public storm sewer or working in the public right‑of‑way often requires permits and may require a licensed contractor per local municipal rules [4][13].
Municipalities vary in rules and many prohibit illegal discharges to public storm drains or neighbor properties — always check your local public‑works or building department before tying into public storm systems [13].
Call 811 (or your state's 811 service) before digging to have underground utilities located and marked; every excavation should start with a utility‑locate notification [12].
OSHA excavation standards require protective systems (sloping/benching, shoring, or a trench box) for trenches 5 feet (1.52 m) deep or greater unless a competent person determines the excavation is in stable rock; a competent person is required for excavation work and for selecting/inspecting protective systems [1][2].
Because of these depth and safety rules, work that requires trenching 5 ft or deeper (typical for footing drains) raises requirements for protective systems and competent‑person oversight, which commonly makes such work better handled by professionals rather than casual DIY [1][2][6].
Also check local permitting requirements before connecting to public storm systems or doing work in the public right‑of‑way; permits and licensed‑contractor rules vary by jurisdiction [13][4].
DIY materials‑only costs for short, shallow runs (pipe, stone, fabric) can be low — tens to a few hundred dollars for short stretches — while professional exterior systems commonly range from a few hundred to several thousand dollars depending on length, depth, soil, hardscape crossings, and whether work reaches footing depth [9][10].
Consumer sites show wide variability: Angi publishes example aggregated installed‑project figures in the thousands for some installs and HomeGuide lists exterior yard/curtain drain per‑foot ranges roughly $10–$35/linear foot while noting interior/perimeter systems can be much more expensive [9][10].
Simple short, shallow yard drains and installs using prefabricated trench units are commonly DIY‑capable for competent homeowners [7][4].
Hire a professional when the job requires deep trenching to footing level, long runs, trenching under or through hardscape, when protective‑system rules (5 ft+ trenches) come into play, or when you must connect to a public storm system that may require permits and licensed contractors [1][2][13][6].
Consult manufacturer and industry design notes (ADS, NDS) for product specifics and sizing, and check local building/utility departments for permit and outlet rules before beginning work [3][4][13].
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