Moisture can ruin house foundation

Q We have a 75-year-old home with a poured concrete foundation. It has started to crumble in plate-sized portions, leaving the crumbled mixture beneath. What is causing this and what should we do about it?

A It sounds like efflorescence, a not uncommon problem in concrete foundations, has developed to the point of spalling, meaning that the concrete pops and flakes off the surface.

What happens is water gets into a concrete wall and dissolves minerals there. When the moisture evaporates, mineral deposits that look like lumps of white or a crusty coating are left behind. Over time, these deposits grow inside the wall, causing the surface to spall, or flake and fall off.

Often homeowners don't see or ignore the efflorescence or mineral deposits. It's an early sign that moisture is getting into the foundation wall. If it is stopped, the efflorescence will slow down if not stop, and further wall deterioration will not occur.

You'll want to keep the water from getting into the wall. A common source of moisture is rain and snow-melt runoff.

• Be sure the gutters are in good working order and that downspouts deposit water well away from the house.

• Check that soil around the house (not just the landscape rock or mulch) slopes away from the house. That includes any sidewalks or driveways near the foundation.

• Consider the plumbing. There might be a slow leak that is allowing water into the foundation wall. Carefully inspect what you can. If you don't find anything, but are still suspicious, call a plumber.

The best way to prevent the problem is to prevent water from infiltrating the wall. If you see efflorescence crystals, it usually means there is a leak somewhere letting outside water in. Once you've found the source of the water and stopped its infiltration, clean the walls with an efflorescence remover.