Document the condition
Document a Naperville property's issue: where it shows up, when, its relationship to weather, how it's evolved, and past repair attempts -- photos and basic measurements are a good start.
Read the local context
A town platted in 1842 along the DuPage River has had a long time to build at different distances from the water, and that is the fact that matters below grade. The oldest in-town blocks sit nearest the river on ground with a correspondingly high water table, and their foundations predate any modern drainage detail. The postwar subdivisions that followed brought poured and block walls whose exterior drainage varied by builder and by year. Across both, the flat prairie ground that made this good farmland drains slowly, so a wall here stays loaded after heavy rain rather than shedding it quickly.
Ask what will be hidden
Water showing up in a Naperville basement might be coming from the roof, the grade, a wall crack, a floor joint, or just humidity -- the entry points differ even when the puddle looks the same. The prep and verification behind a finished Naperville job disappear from view once it's done, so the written scope has to account for them.
Compare complete scopes
Evaluate Naperville proposals side by side for protection, access, materials, permits, testing, cleanup, restoration, exclusions, warranties, and change-order provisions.
What official local sources add
Two of the city's requirements bear directly on below-grade work. Naperville requires property owners to maintain on-site stormwater control facilities, which is the question a waterproofing proposal has to answer: a system that collects water at the foundation must discharge somewhere the stormwater plan actually anticipates, not simply a few feet from the wall. And because the city's plan relies on detention basins and overflow routes, a property's position relative to those routes explains a great deal about why water arrives when it does. Where the parcel sits within DuPage County, the county floodplain regulations Naperville has adopted apply on top.
Current as of the 2026-07-26 review -- confirm a Naperville parcel's flood zone, historic-district status, permits, and requirements before authorizing work.