A French drain should be selected for a defined water problem. Before discussing pipe and gravel, ask whether the concern is water flowing across the surface, water moving through the ground or another source such as plumbing. The name of a system does not establish that it fits the site.
Ask the contractor to describe exactly what they mean by French drain. Different proposals may use the term for different collection arrangements, making price comparisons misleading.
Start with the water route
Record where water first appears and what happens after rain. Mark roof outlets, low areas, paved edges and any existing drain features on a sketch. Identify which observations are known and which are assumptions.
OSU Extension discusses subsurface drainage with attention to outlets and sediment-related maintenance. Its guidance supports asking for the complete system and access plan. OSU Extension: Addressing Drainage Issues in the Urban Landscape (2020)
| Design question | Detail to request | Why it matters |
|---|---|---|
| What water is collected? | Source and collection method | Confirms the system’s purpose |
| Where does the route run? | Plan with existing features | Reveals access and conflicts |
| Where does it discharge? | Verified destination | An inlet alone is incomplete |
| What existing pipe is reused? | Condition and outlet check | Avoids relying on unknown piping |
| How is it maintained? | Accessible cleaning points | Supports future service |
| What remains untreated? | Written exclusions | Prevents overbroad expectations |
Compare surface and subsurface proposals
If ponding is visible on a patio or lawn, ask how water reaches the proposed collection system. If seepage is suspected, ask what evidence supports that explanation. The proposal should connect the observed source to the chosen method.
Do not assume a buried trench will solve every surface low spot. Ask whether grading, an inlet or another measure is required and whether it is included. If several options are offered, have the provider compare them against the same observed problem.
Verify the outlet before excavation
Request the discharge location and the basis for using it. Ask how the route works with the available site levels and any applicable discharge requirements. Do not direct water toward a neighbor or unidentified buried line on the assumption that moving it away from one wall is sufficient.
If the plan depends on existing piping, ask how its route and condition will be established. A drawing should distinguish confirmed information from a line that has merely been assumed to connect elsewhere.
Keep roof drainage identifiable
Ask whether downspouts have their own defined route. DOE/PNNL guidance distinguishes roof-water conveyance from perforated foundation drainage. An unidentified shared connection deserves clarification before it is reused. DOE/PNNL: Gutters and Downspouts (2021)
Label the functions on the final drawing. Future maintenance becomes easier when an owner can tell which pipe collects groundwater and which carries roof runoff.
Specify installation records and restoration
Before work begins, identify access areas, disturbed landscaping and the finished surface. Request photographs of concealed components before they are covered. Ask for cleaning access to remain reachable after planting or paving.
The scope should describe how unexpected obstructions or unsuitable existing components are handled. Agree on written approval for changes instead of relying on a verbal decision made while the trench is open.
Evaluate performance over time
Ask the provider what observations will demonstrate whether the intended problem improved. Record rain timing, remaining ponding and any outlet obstruction. Keep maintenance instructions with the route sketch.
A future wet area may have a new source or fall outside the original scope. The documentation should make that boundary clear without treating every recurrence as either automatic failure or normal behavior.
Frequently Asked Questions
Does every foundation need a French drain?
No. The selected system should respond to a diagnosed water source and a feasible outlet.
Can I connect a downspout to any buried drain?
Do not assume compatibility. Identify the pipe’s function, condition and destination and obtain a suitable design.
Will a French drain repair foundation movement?
A water-management project should not be treated as a structural repair specification. Ask whether a separate building assessment is needed.
Related Services
Visit foundation repair or request a drainage assessment.
Research Sources
Sources reviewed September 6, 2026. Inspection and quote questions are an editorial checklist; actual repair requirements depend on the property.