When we are called out to bid a job, the damage, as they say, is already done. In this post we will be discussing the cause of most settling and what you can do to insure your slabs remain stable after we leave.
There are two primary issues that cause concrete to settle and they are often related; soil compaction and excess water. If you have settled concrete you likely have one or both of these problems, so, what to do?
Let’s discuss the first issue, compaction. After the home is built it is nearly impossible to effect the deeper layers of the earth around your home so unfortunately, if your builder failed to compact, which is the rule not the exception, time will have to take its toll. Typically the major settling will take place in the first two or three years and by year seven or so, you’re generally finished with the worst of it.
The second issue, dealing with excess water, can be frustrating, especially if no thought was put into dealing with the inevitable rain and snow melt when the home was being built. So, what can be done after the fact?
1) Install gutters and down spouts. Down spouts should be directed at least five feet away from foundation walls and from walks and other concrete slabs. Of all the slabs we raise, the most common is the one right in front of the entry. Why? A down spout, or roof design is nearly always dumping water at that point.
2) Do not plant bushes or sod near foundation walls or sidewalk slabs. A good rule of thumb is to allow five feet between the foundations and plantings and two feet between walks and plantings. Plantings too close to walks or along foundation walls, cause root issues, erosion issues, and compaction issues. A Slabjackers paradise! Something to remember, most trees and bushes have a root system that is 50% larger than the width of the canopy. That nice looking Japanese Maple that is nearly touching your eve has roots extending along your foundation and under your sidewalk. Water follows the roots and before long you have voids that further take top soils away and settling is well on its way. For an interesting example of what roots can do to a driveway, go to our web site www.SlabjackGeotechnical.com and in the before and after pictures look at the driveway photo. (We had to raise three additional slabs to match the one that was raised)
3) Maintain fill along slabs, fill in any erosion you see prior to settling occurring and if all else fails, call us when the settling starts, before cracks develop, to raise and stabilize your slabs.
4) Give your sod and plantings the absolute minimum amount of water to keep them healthy. Turn your sprinklers down until the sod begins to suffer then turn it up slightly. Too much water cause funguses, such as necrotic ring spot and mushrooms to grow and some soils such as clay, allow concrete slabs to settle because water saturates, then drains very slowly through them. A good example of this is a job we did in the Wenatchee area; a sidewalk was settling, inspection showed fully saturated clay down to a depth of over six feet! We could literally stick a probe two feet into the ground with one hand! We advised the home owner to turn off her water for a week and to reduce the timer to ten minutes on that zone verses the forty minutes it was programmed for. Too often what sod needs is nitrogen and it keeps getting more water because “it isn’t green enough”
The key to stable concrete is a stable base, you can’t do much about compaction after the fact but you can reduce waters role in the equation. Plant well away from foundation walls and walks, reduce sprinkler timers to only what is needed. If water is pooling you may have clay soils and need to further reduce watering. If flooding occurs or you notice soils have washed out along slabs, replace the fill as soon as possible. Finally if you notice settling call the concrete raising and leveling professionals 1-855-752-2522, the answer to settled and sunken concrete all across Eastern and Central Washington.
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