The following is a good article about foundation cracking. Cracks in foundation walls, to the untrained eye, are all serious when in fact that is untrue. As a native of the Denver Metro area and very knowledgeable of the expansive soils here it is in the best interest of your client that you have a knowledgeable and trained eye to detect if is truly serious or minor and superficial.
Cracks in Basement Walls
by Gerry Aubrey of Blue Bell Consulting, Inc.
When spring arrives we generally focus our attention on cleaning the house, cleaning the yard, and planting gardens. Before we venture out, let's head to the basement and check something really important: the basement walls. Winter is brutal. Freeze thaw cycles destroy streets and frozen rain pulls down wires and trees. Those same forces are busy below grade, and they can wreak havoc on the home's structure. When the ground freezes, it swells and pushes against the foundation. This pressure can crack the wall, resulting in serious damage to the home. Almost 1/3 of the claims made against home inspectors are related to structure. The vast majority deal with structural failures discovered after renovations begin and were not visible to the inspector, but the central issue is the structure which is very important. A house is only at strong as its' foundation.
The first order of business is pull everything away from the walls so you can see all sides, top to bottom. If you finish your basement, build the walls out far enough so you can examine the foundation. What type of walls do you have? A rule of thumb, stone is the best. This is only present in very old houses, but it's the most solid foundation you can have. Poured concrete is the next best thing to stone. You are inspecting it to find damage that can result in structural failure. Concrete foundations often crack. The crack is usually vertical. It is caused by shrinkage of the concrete as it cures. If you find a vertical crack, rub your fingers across it. If both sides of the crack are even, the crack is most likely from shrinkage. This is a common cracking pattern and is rarely a structural concern. If you have water entering through the crack, get it professionally repaired. If you can fit a dime in it, get it fixed. Occasionally the wall on each side of the crack is not even. This type of crack may have been caused by a backhoe operator in a hurry. Walls are sometimes cracked during the backfilling process.
If you have cinderblock walls, they are most prone to problems. If properly installed and maintained, they generally perform well. Again, a vertical crack is usually not a concern. The wall is merely segmented, and the wall on both sides of the crack is doing its' job. Look for water penetration, and if present get it repaired. If you find a long horizontal crack in the wall, you should be concerned. A horizontal crack compromises the integrity of the entire wall. It can lead to catastrophic structural failure. If you can put a dime in the crack, call a structural engineer. These horizontal cracks usually appear about 3' below grade. They are caused by hydrostatic pressure against the side wall, and it snaps the wall. If I find a small crack during an inspection my advice is often to monitor the crack. If the crack never changes, you need not worry about it.
Monitor the crack? The Client generally looks at me like I suggested they study Latin Literature. Cracks are like a stain on the ceiling, it's very difficult to tell if it changes. There is a device that I've discovered for monitoring cracks that is brilliant in its' simplicity. It is manufactured by Avongard Products of Santa Monica California. They have a toll free number to order it, 1-800-244-7241, and the device, with shipping, is less than $20.00. It consists of two pieces of clear Plexiglas with a grid on them and two holes in each piece to secure it to the wall. It comes with a chart that duplicates the grid, and a spot on the chart to write the date. The device is secured to the wall and the grid is placed over the crack. You can secure it with masonry nails or an epoxy that the manufacturer sells. Once it is secured to the wall, you cut the tape that joins the two pieces of Plexiglas. The two pieces will move slightly when you cut the tape. You then draw a line on the chart to duplicate the reading on the grid. Keep the chart in a safe, dry place, and re-inspect the crack regularly for at least a year. Mark the next grid on the chart and date it each time you check it. The soil conditions can vary greatly between the seasons, so it takes a while to be sure there is no movement. Monitor it for at least a year. If the crack is moving, call an engineer.
When I find a crack in a basement wall, the first thing I try and determine is what the crack has been doing lately. Cracks caused by backfill, or water damage ten years ago are far less of a concern than a crack that is moving. If there is evidence of moving, a specialist should be called as soon as possible. There are a multitude of methods to repair foundation walls, short of tearing the house down and starting over. They obviously will vary in price depending on the labor involved. One thing is certain. If you have a crack in the basement wall, check it regularly, and if you are at all suspicious of it moving, call an expert, and get an expert to repair it. This isn't the same as painting the back porch. If the job's not done right, the down side can be disastrous.