September 26, 1996

Home inspector tells how to take the stress out of cracks

By Dan Bowers - Holmes Inspection Co.

Cracks in the walls are not restricted to homes owned by the Addams Family or Dr. Frankenstein. Cracks are found in most homes, but you’ll be glad to know that in most cases, they are not related to structural problems. Approximately 80 percent of the cracks we see in residential structures are horizontal, vertical or diagonal. A large number are minor and do not require repairs outside of some basic caulk and repainting.

The following will help you better understand which racks are potential problems and which are not:

Horizontal cracks

Horizontal cracks are usually structurally related. However, their significance depends on whether there is lateral movement and, if so, how much.

If a wall has moved one-third of its thickness out of plumb, it is in imminent danger of falling. If it has not moved, or if the movement is less than one-third of its thickness, the wall can probably be reinforced.

Vertical cracks

Vertical or nearly vertical cracks are only structurally related when there is lateral movement (bow or shear, for example). This assumes the crack is a consistent width from top to bottom.

In most cases, vertical cracks are hair line or slightly wider and are caused by normal shrinkage or contraction. Expansion and contraction are normal for building materials. The more rigid the material is, the more likely it is that a crack will develop. Porous or less dense materials will be flexible and less likely to crack.

Vertical cracks in a wall with a bow or sheared wall planes are structurally relat ed; Contraction cracks are hardly ever a structural concern.

Diagonal cracks

Diagonal wall cracks that break through the building material are almost always structurally related. Step cracks in a block wall that only crack at the mortar joints and not through the block wall are not typically a structural problem unless lateral movement is present.

When the bearing or foundation under a wall is not adequate, the wall will settle or sink at the weak area.  The adjacent wall structures that are adequately supported will resist this movement.  This situation will typically cause diagonal cracking.

To determine the cause of a diagonal crack, draw a line perpendicular to the crack down from the approximate center of the crack.

Dan Bowers is a certified member of the American Society of Home Inspectors.