Start with the water path
The Department of Energy’s introduction to moisture flow separates four ways moisture moves: bulk water such as rain or groundwater, capillary movement through porous materials, moisture carried by air, and vapor. A proposal should say which one it addresses rather than using “waterproofing” as a catch-all. A pipe leak, water coming through a foundation detail, and condensation should not automatically get the same recommendation. Ask the assessor to sketch the suspected route from source to basement and mark what is confirmed and what still needs investigation.
What exterior work is meant to do
DOE’s foundation-wall guidance describes a damp-proof coating or plastic drainage plane on the below-grade wall, plus a gravel layer that lets water flow down to a perforated drain pipe at the footing that carries it away from the structure. The coating, drainage layer and drain are separate parts, not interchangeable names.
Ask which sides of the foundation are included, which parts will be installed or repaired, where collected water will discharge, and what happens to paving, planting or steps disturbed for access.
What interior drainage is meant to do
A DOE case study of interior foundation retrofits describes a membrane with a small gap against the wall whose drainage space is directed to a drainage system at the base of the wall, such as a channel above the slab or a perimeter drain under the slab edge. That study covers specific cold-climate masonry assemblies; it is not a design for every basement.
Ask how water will be collected, where it goes, and what moves it to the outlet. If a pump is included, ask about maintenance access and what happens during a power loss or pump failure. Our article on sump pumps and dehumidifiers explains what each device does.
What neither label tells you
Neither phrase tells you whether a plumbing leak, damaged finishes, or a humidity problem is included. The EPA’s guide to mold and moisture stresses fixing the water problem as well as cleaning up after it. Ask whether assessment, water control, drying, any contaminated-material work, and finish restoration are separate items. If you plan to finish the basement, have the wall and floor plans reviewed together with the water-control plan.
Compare the explanation before the label
For each proposal, write down the evidence for the water source, the collection route, the discharge point, maintenance needs, exclusions, and how success will be checked. If water has just appeared, start with what to document when water appears in your basement. Leave excavation, foundation changes, drain installation and electrical connections to qualified professionals. More questions are on our waterproofing page.