Foundation types you may find in central and east Denver
| Foundation | Where it tends to show up | Moisture behavior |
|---|---|---|
| Brick | Early twentieth-century homes, such as parts of Congress Park and Hale | Porous; mortar joints erode and pass water and salts |
| Hollow concrete block | Mid-century homes and many additions | Cores can hold water; dampness shows along mortar lines |
| Early poured concrete | Many 1940s and 1950s homes in Hilltop, Mayfair and Crestmoor | Fewer joints but cracks and form-tie holes admit water |
| Stone or rubble | Occasional older houses and outbuildings | Irregular and very porous; often damp along the base |
| Modern poured with membrane | Rebuilt homes and recent additions | Better protected, but depends on drainage and the membrane staying intact |
Why masonry keeps smelling
Brick, block and concrete are not waterproof. They draw moisture from the soil and release it into the basement air, a process sometimes called capillary rise or wicking. In older homes the exterior dampproofing, if there was any, has usually long since broken down. The result is a wall that may never look wet but stays slightly damp all year.
That moisture carries dissolved salts. As it evaporates on the inside face, the salts are left behind as white crust, called efflorescence. Efflorescence itself doesn't smell, but it marks where water is moving. Dust, cobwebs, paint and anything stored against that wall can then grow mildew and produce the familiar musty odor.
Paint and sealers can make this worse if they trap moisture. Old latex paint peeling in sheets, crumbling parging, or a bubbled waterproofing coating are signs that water is pushing through from behind. Covering the wall with framing and drywall without addressing the moisture tends to move the smell inside the wall cavity rather than eliminate it.
Reducing odor from a damp masonry wall
Start outside
Look at the soil, gutters and downspouts on that side of the house. Grading that slopes toward the wall and short downspouts are the most common contributors and the cheapest to change.
Clear the wall
Pull stored items, cardboard and furniture away from masonry walls by several inches so air can move and you can see the surface.
Clean the surface
Brush off efflorescence dry with a stiff brush. Clean any mildew with an appropriate cleaner, following the label, and let the wall dry.
Control humidity
Run a dehumidifier sized for the space and keep relative humidity in the commonly recommended range of roughly 30 to 50 percent.
Repair the masonry
Repointing eroded mortar or repairing parging is mason work. Ask about breathable materials suited to older brick.
Consider the whole system
If dampness persists, a waterproofing contractor can discuss interior drainage, exterior membranes or both. Get more than one opinion.
Common questions
Should I seal the inside of the foundation wall?
Interior sealers can help in some situations, but on old brick or block they can also trap moisture and cause spalling. Ask a mason or waterproofing contractor which product, if any, suits your wall.
Does efflorescence mean the wall is failing?
Not necessarily. It shows water moving through the masonry. Heavy buildup, crumbling mortar or flaking brick faces are more serious signs.
General information for Hilltop, not a quote or professional advice. In an emergency, call 911.