Core TradesQuestion 66 of 700

A below-grade concrete basement wall shows persistent damp spots and mineral staining on the interior. The MOST effective long-term remedy is to:

a.Paint the interior with latex paint
b.Run a dehumidifier continuously
c.Excavate and apply exterior waterproofing with proper drainage at the footing
d.Add more interior insulation

Explanation

Water intrusion in below-grade walls is best solved on the positive (exterior) side by excavating, applying a waterproofing membrane, and installing footing drainage to relieve hydrostatic pressure. Interior paint and dehumidifiers only mask symptoms; insulation can trap moisture and cause mold.

Law Reference: 2025 CA Building Code, Chapter 18 (Foundations)

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