Wisecracks are a series of "collector's edition" prints of home defects that we've accumulated over the years. These specifically show different cracks in structural systems. The "wise" part is where we explain that sometimes a crack is just a crack, and sometimes it is a symptom of a very serious problem. The art of home inspection is in being able to distinguish between the two, and to offer meaningful advice to a client on how to proceed. A skilled home inspector is trained in defect recognition, and a very skilled home inspector can often make a field diagnosis with enough certainty to put you on the right track to solving the problems.
Card 1 - When a Crack is not Just a Crack
This picture shows a classic failure of an older masonry foundation wall. The network of cracks runs horizontally the full length of the wall. The wall is also bulging inward about 3 inches from top to bottom. Horizontal cracks are almost always a serious structural issue, and when the wall is bulging as well, they indicate a serious and sometimes immediate problem.
In this case, the wall is made from brick, and it is over 100 years old. Even though it has taken 100 years to move this far, that is not cause to ignore the problem. Once the wall bulges this far, the process often accelerates. Eventually, the wall can fail catastrophically and suddenly. This one is probably not a candidate for repairs. Call a foundation contractor for replacement.
Some typical "rule of thumb" measurements for foundation walls: 8" brick foundations can usually retain about 4-5 feet of soil, 8" block can sometimes retain 5-6 feet of soil, reinforced concrete can retain 8' or more. Walls that are bowed more than about 1/8 of their thickness are in immediate distress and should be repaired or replaced. Consult with a licensed structural engineer for full diagnosis and repairs.
Card 2 - Some Cracks Try to Hide
This horizontal crack neatly follows the sewer pipe, and hides behind the electric panel. The crack also has been further hidden by repointing type repairs, to no avail.
"Repointing" a crack is the process of packing new mortar into a cracked mortar joint. Done well, the mason will grind the existing mortar out of the joint ½" -1" deep, clean the joint, and then repoint with hydraulic cement that expands as it cures. More typically, what's called "repointing" consists of just smearing some ready-mixed mortar over and onto the crack. Either way, repointing is never a structural repair.
If a horizontal crack is stable, repointing may provide a long-lasting cosmetic repair, and the new mortar does provide a handy tool for measuring continuing movement - if the joint cracks again, the wall is still moving and the crack is NOT stable.
In the picture shown, the crack is definitely not stable. It has been repointed several times, and it has cracked again. The crack is relatively wide, and more importantly, the wall is bowing inward. This crack requires evaluation by a structural or geotechnical engineer for specification of structural repairs or replacement.
Card 3 - Upstairs, Downstairs
Stair-step cracks like these are sometimes serious, sometimes not. This one indicates that the soil underneath the middle of the wall has settled, and the foundation has followed suit. This type of settlement can sometimes stop on its own. Crack monitors can be installed on the wall. If the wall has stabilized, only minor patching and repairs are necessary (see Repointing, above). If it is still moving, more significant repairs may be required.
This type of soil settlement can occur for a variety of reasons. The most common are: improperly prepared soils, compressible soil layers, and organic debris below the footings. In the first case, it is common for the settlement to progress to a certain point and then stabilize. With compressible soils, the settlement can also stabilize, but sometimes there is enough differential settlement to cause substantial distress throughout the building. With buried debris, sometimes the settlement does not show up for many years, and then it can continue for many years after that. The only way to tell for sure what is causing any specific case of settlement is to have an engineer perform soil sampling and core drilling to determine what types of soils underly the foundation, and what repairs might be necessary.
Card 4 - Why do Cracks Happen?
Block walls often fail about a foot below ground level, due to the combined pressure of the soil outside, and often water and ice. As a rule of thumb, a typical 8" block wall can hold back about 4'-5' of fill for the typical soils found in our area. A 12" block wall can retain nearly 8' of fill.
If there is a deep basement, and if the amount of fill against the wall exceeds these numbers, the sheer weight of the soil often causes the foundation wall to crack and slowly buckle. Even if the weight of the soil is insufficient, a surcharge of water in the soil (from clogged gutters, improper drainage, etc.) can often add enough pressure to cause the crack initially, and then the wall failure slowly progresses after that.
Horizontal cracks such as these are also commonly caused by the builders themselves during construction. If the backfill is placed against the wall too soon, if the wall is not braced properly when the backfill is placed, or if heavy equipment is operated too close to the foundations while they are still fresh, they can easily be broken. Sometimes these fine cracks are not noticed for many years.
Still, any horizontal crack is considered to be a structural failure of the foundation, and it requires repairs, specified by a licensed engineer.
The basement in the picture also has a few other common home inspection issues: The washing machine drains into the sump pit, and the sump pump drains into the sewer: both are prohibited practices.
Card 5 - The Plumber Did It
The crack in this nearly new floor joist starts at the lower left corner of the notch made by the plumber for the waste pipe. The Codes control how joists can be drilled and notched for exactly this reason. The graphic below shows acceptable boring and notching for solid lumber floor joists.
The damage in this case can be repaired by sistering another new joist against the damaged one. It is important to properly fasten the two together, generally with many nails. This is typically an inexpensive repair.
Card 6 - Builder Damage
Sometimes cracks happen during construction. This roof truss was broken before the homebuyers even moved in. Truss repairs are sometimes complicated, and always require design by a truss engineer. A single broken truss can result in roof collapse during storms, so repairs are important.
Card 7 - Settlement
The term "settlement" is often used as a catch-all for normal cosmetic issues that often occur in new houses as they dry out and settle-in. When Engineers use the term "settlement," they mean something serious has happened. In this case, the soil under the corner of the house is unstable, similar to the soils below the foundation in Card 3, above. It has settled under the weight of the house, and the foundation is broken. Sometimes, this soil settlement continues for many years.
Often, a house is placed on a "cut & fill" lot, and one side of the house is placed on the fill. If the fill is not properly prepared, it will often compress, and the house will break in the middle. If only a small portion of the house is placed on the fill, a broken corner like this may result.
Card 8 - Shrinkage vs. Settlement
Concrete slabs shrink when they cure, and sometimes shrinkage cracks are the result. Most of the time, cracks in concrete floor slabs are the result of shrinkage, and they seldom require structural repairs.
The cracks here, however, are due to settlement of improperly prepared soils under the slab. As the soils compress, they can leave large voids under the slab, and the slab then cracks and settles into the voids. Over time, they can become serious and they are usually expensive to repair.
Card 9 - Who bent my house?
At the lower right corner, you can see the edge of the original foundation where the addition was attached. Unfortunately, the builder did not install proper foundations under the addition, and it is settling. As the back of the house settles into the ground, the foundation forms a "hinge" at the area shown.
Brick veneers are an excellent tool for identifying structural settlement. Because brick is a brittle material, it tends to crack rather than simply bending. The pattern of cracks in brick or other masonry structures can provide very useful information to the engineers diagnosing them.
In this example, the crack is the symptom, not the problem.
Card 10 - New Houses Crack, Too
This finished porch on a newer house has severely settled away from the house. There were foundation cracks, sheetrock cracks, trim separation, and all of the signs of structural settlement. The repairs are both important and expensive.