This picture was taken from a foundation case our firm was involved in. As you can see, without a doubt, the most irritating aspects for a builder and homeowner, and one which causes so much litigation, is concrete. It comes in many forms, depending upon where you live, but here are a few common issues:
- Severe cracking
Let’s take a look at these individually. Keep in mind, where you live and the type of soils you have under your foundation matters. Cut/fill lines, percentage of organics in the soil, drainage, loam vs. clay/bedrock and mass grading issues are all important determinative factors in how any foundation will perform. Thankfully, the science of concrete has come a long way to increase the success rates of foundations.
I have seen many cracks in my time as developer counsel, no pun intended. Cracking is one of those items that neither a contractor nor a homeowner will notice until an intervening event occurs to the structure. These issues usually arise after curing and the weight of the structure has been placed on the slab. Depending upon the depth of your footings, and the type of slab used (post-tension, slab on grade or post-tension), the better the slab structure, the less chance of cracks occurring. Keep in mind your soils will move over time, regardless – it happens.
What we typically see as possible signs of severe slab cracking include cracks in the exterior fascia of the structure (brick/stucco/stone veneer and possibly bending to the siding), cracks in the flooring and door misalignments to the framing. At my ranch, I have had a tree root migrate under my slab. I discovered this one night when I thought I heard someone slam a stack of dishes on the floor. The tile had buckled under the upward pressure from the root pushing on the slab. I can tell you I had no notice of a root growing under my slab. Yes, things like this even happen to construction lawyers.
Hairline cracks are not uncommon, and usually do not present an issue for slab integrity. Most of the time, you will never know a thin crack is present under your flooring. When it comes to cracks that start at ¼ inch in width, you begin to see manifestations of a greater problem within your home. You need to regularly inspect, at least once a year, for any issues with respect to your flooring, exterior of the home, and surrounding soils. If you notice anything out of normal, consider inspecting deeper. A concrete inspector may be able to conduct some level readings or manometer tests to determine if your slab has heaved or is sinking. Usually, the fix may be as simple as an epoxy injection into the crack with taping or even saw-cutting out the crack and re-laying new concrete.
Keep in mind that severe cracking is a common result due to the next two items being the cause.
How many times have you heard the phrase “The house is just settling.” Well, what you may consider a nonchalant term to explain away noises in your home, has much graver consequences in real life. Settling of slabs is very common. It is usually occurs from a poorly-graded/compacted pad. When the slab is poured in these conditions, air can pocket. As the structure settles in after completion, the weight will cause the air pockets to push into the soil. The soil then sinks and can cause unevenness in the slab or even cracking in extreme situations. Hence, your concrete slab “sinks.”
Concrete depends upon the soil conditions. The amount of organics in the soil prior to pouring the slab can also affect settling. If the organic content is too great, then no solid soil compaction can be maintained over time. This too can cause settling of the structure.
In the same way, cut/fill lines (infamous on structures placed on hills) can cause settling and divergence in the plane of the slab. I once inspected a home on a 120-foot cut/fill line. When I walked in the front door of the home, I began walking downhill towards the dining room. That was one for the books with over a 4-inch slab deviation in level.
Again, as with cracking, keep your eyes open on your structure. Inspect things you see as slight deviations. The structure will usually let you know where the problem arises, but you have to be diligent in inspecting and observing.
On the other end of the spectrum, a slab that lifts up (heaves up) can usually be attributed to poor soil and/or water infiltration. In this instance, much like the soil conditions which cause settling, high organics or loamy soil retains the moisture from irrigation, rain or other occurrences. These types of soils can absorb large amounts of water, perching it under the slab. The swelling soils uplift or heave upward, causing the slab to rise in various locations. It is difficult to see with the naked eye, but usually your edges of the structure appear lower than the middle portion. A secondary problem associated with this type of condition due to water is efflorescence or water percolation through the slab. This can be abated by a high-quality vapor barrier.
Some solutions for settling and uplifting of slabs includes mudjacking, the process by which concrete is injected under a slab to re-level it. This usually insures levelness for the life of the slab. Other methods can be to install concrete piers around the edges of the slab, which will hopefully avoid future movement in either direction.
The moral of the story is that the ground moves and soil is permeable. And, most important around here, make sure your flower beds are not holding any water, that water runoff is not moving or perching next to the seals, that your gutter exits are extended away from the foundation, and that runoff from the roof does not perch around the foundation. Spending the extra time and money on high-quality geotechnical evaluations, concrete mixes, and slab reinforcement will go a long distance in keeping the integrity of your structure for the duration.