Signs an old foundation is failing, and what each one means

Most people never really look at their foundation. It is dark, the walls are behind shelves and the furnace, and nothing seems wrong until something obviously is. So the first step is simple. Clear a path along each wall, take a good flashlight, and look at the whole thing from one end to the other.

You are looking for movement, missing material and water. Those three tell you almost everything.

Stand at one corner and sight down the wall. A sound wall is straight. A wall that bellies into the basement in the middle, or leans in at the top, is being pushed by the soil outside. In this part of Illinois that soil is heavy and wet for long stretches, and when it freezes it expands and pushes harder.

A small bow that has been there for years and is not changing is one thing. A bow that is getting worse, or a wall that has cracked along the line of the bow, is the most serious sign on this list. It is the one most likely to end in replacement.

On a stone foundation, press on the stones with your hand. They should not move. If they rock, or if you find stones or chunks on the basement floor, the wall has lost its grip on itself. On brick, look for brick that is cracked through, missing, or has its face falling off in flakes.

One loose stone is a repair. Loose stones all along a wall usually mean the mortar has failed throughout.

Old foundations were laid in lime mortar, which is soft by design. Over a long time, water dissolves and washes it out of the joints. Scratch a joint with a key or a screwdriver. If the mortar rubs out like sand, or there is a pile of it along the bottom of the wall, the joints are empty or close to it.

Sandy joints alone can be repointed. Sandy joints plus a wall that is moving is a bigger conversation.

Water through a foundation shows up as wet spots, puddles after a rain, dark stains that come and go, and a white crusty powder on the wall. That powder is salt carried out of the masonry by water as it dries. It is not dangerous by itself, but it tells you water is moving through the wall regularly.

Look at when it happens. Water only after heavy rain often traces back to downspouts or grading. Water every spring for weeks points to the ground staying soaked against the wall.

Hairline cracks are common and often harmless. What matters is whether a crack is changing. Put a pencil mark at each end of the crack and write the date next to it. Check it after the next winter. If it has grown longer or wider, or one side has pushed out past the other, the wall is still moving.

In block walls, a horizontal crack partway up the wall or a stair step crack through the joints is more of a concern than a straight vertical one.

A failing foundation shows up in the rest of the house too. Doors that start to stick or swing open on their own, floors that slope toward one side, cracks in plaster running out from the corners of doors and windows, and a gap opening between the house and a porch or addition. None of these prove the foundation is the cause, but together with what you see downstairs they paint a picture.

• Doors and windows that stick or will not latch
• Floors that slope or feel soft near one wall
• Plaster cracks from the corners of openings
• A porch or addition pulling away from the house
• Gaps between the siding and the foundation

Take photos of what you found. A wide shot of each wall and close ones of the worst spots. Then go outside and photograph each side of the house so the downspouts and the slope of the ground are in the picture. Text them with your town to (217) 549-2230. Brian Lee Smith will tell you if you are looking at a repair or a replacement.