How We Diagnose
Grades first, then the outlet, then the cause. Surface water from a settled grade or a downspout at the wall is the most common finding and the cheapest to fix. Groundwater moving laterally needs a drain. Water through a specific crack under pressure needs that crack addressed. They look identical on a basement floor and cost very different amounts.
How We Build
Washed rock and filter fabric, never native clay backfill. Drains backfilled with the soil that came out of the trench silt shut within a few years, and that is the single most common reason a french drain stops working. More on how we build them.
What We Will Tell You
When the honest answer is a downspout extension rather than a full system, that is the proposal you get. We would rather do the small job correctly than sell the large one.