Basement Moisture: Everything Homeowners Need to Know
Part 4: How Do I Know if I Have a Basement Moisture Problem?
Part 4: Besides stepping in a puddle or seeing the water rushing across your basement floor, there are some common signs of moisture issues. Being aware of these can help you ask important questions when considering the purchase of a home.
Standing Water
Don't write off the puddle in the middle of your basement floor as a problem from above. There is a strong likelihood that hydrostatic pressure has pushed ground water up through the basement floor and a puddle has formed. This can be common in areas with a high water table or during extended times of heavy rain.
Efflorescence
A visible and easily identified symptom of moisture issues is the presence of efflorescence on your concrete or stone foundation walls. Efflorescence is a white crystalline substance that will appear and “grow” on the interior of the wall. This is a deposition of salts left behind from water than has evaporated. Various mineral salts exist within the foundation stone and mortar, these are typically sulfates and carbonates, including compounds of sodium, potassium, calcium, and magnesium. One can somewhat compare this to limescale, which is calcium carbonate left behind from evaporated water. With efflorescence, small amounts of moisture moving through the wall will dissolve these salts and once the water hits the interior of the home the water evaporates and those salts are left behind. Efflorescence is extremely common, it’s also the white substance you see on some exterior brick faces. Efflorescence itself doesn’t cause any harm and does not weaken the structure, although it is aesthetically displeasing. The key thing about efflorescence is that it indicates a moisture issue behind the wall.
The efflorescence pictured here is fairly light, a little efflorescence over a long time in an unfinished basement is common.
Spalling
Unlike efflorescence, spalling does indeed damage the structure of the block. Spalling is when concrete or brick begins to flake, pit, or chip on the surface. In many instances this can be related directly to water infiltration. In an outdoor environment it accelerates with freeze thaw cycles in the winter. We typically don’t need to worry about freeze-thaw inside but excessive water infiltration and constant hydrostatic pressure can lead to spalling as well. Spalling can also happen with improper mixing and setting if you have a poured concrete foundation or poured basement walls.
Basement and Foundation Wall Issues
A limited number of hairline cracks are common and normal in any foundation that is at least 10 years old. These are created by the settlement of the home slowly over time. Generally these are not problems and can be sealed to prevent moisture and pests. That said, there are some key things to look for that can signal problems.
Is the crack greater than ¼ inch wide?
Is the crack noticably wider at one end than the other?
Is the crack long and horizontal?
Is the crack “stair stepping” along the mortared joints?
Is the wall leaning in at the top or pushed in at the bottom?
Is the wall bowed in down the middle horizontally or vertically?
If you answered yes to any of these, they are common symptoms of a potential water problem behind the wall. These problematic issues show that the wall has been compromised and is experiencing non-uniform forces and movement. If your home has any of these issues it's best to have them checked out by someone who can assess the problem and the fix: a structural engineer. Your home inspector and realtor can guide you through the assessment.