Foundation painting — moisture protection, preparation, and conditions
Foundation painting isn't just about aesthetics — it's the most important visible part of your home's moisture protection. An unpainted or damaged foundation lets moisture into the concrete, where freeze-thaw cycles cause damage winter after winter.
Foundation painting demands stricter conditions and more thorough preparation than other exterior surfaces. This guide covers the steps for concrete and rendered foundations, moisture testing, product types, and the conditions needed for a successful result.
Why does the foundation need paint?
Concrete is a porous material that absorbs water by capillary rise from the ground and rain. An unpainted foundation gets wet, and in winter, freezing water expands in the concrete's pores — the result is frost damage that crumbles the foundation year after year.
A breathable foundation paint or coating protects the concrete from external moisture while allowing internal moisture to evaporate. Non-breathable paint (like standard latex) traps moisture inside and peels off quickly.
Concrete vs rendered foundation?
Preparation and product choice depend on the foundation type:
- Concrete foundation — the surface is usually smooth and even. Brush away loose material and weathering with a wire brush. Fill holes and cracks with cement-based filler.
- Rendered foundation — the render may be lime, cement, or thin-coat plaster. Remove loose render, repair damage with matching mortar, and allow to dry before painting.