Kansas City Real Estate Thoughts...
Expansive soil is common in the Kansas City area and clay dirt is a prime example of an expansive soil. So dealing with it is a necessary evil when it comes to new home construction in the area. I’ve been a partner in several Kansas City new home community developments and when you’re around construction enough you quickly learn that clay dirt will swell when particles in the clay begin to absorb water from rains, underground springs or watering of your lawn. Years ago an engineer told me that clay soil can expand around 10% when exposed to moisture. Since expanding soil can cause upheaval of foundation walls, basement floors, driveways and patios this is a concern. More often than not the result is minor cracking of concrete and, since cracking is inevitable in all concrete, it may be impossible to determine if the cracking is a result of expansive soil or were bound to happen irregardless. Side note: I’ve added concrete cracking to my death and taxes “guaranteed to happen list”. If expansive soil is located on a single-family residential lot, there are many remedies I've seen to stabilize the structure being built. One of the remedies includes spread footings, which means doing a wider footing than is typically installed. Another option may be adding more than typical numbers of rebar into the concrete. Rebar is reinforcing steel that is placed within the concrete when it is being poured. Another option is "piering" down to virgin soil, which would thus place the base of the foundation on solid ground. It can be nearly impossible for area homebuilders to produce the perfect construction conditions but in perfect world clay soil would never be dry when foundation footings are poured. Conversely, water would never be left to pond around the foundation before, during or after footings and foundations are poured. Unfortunately, producing perfect conditions are often impossible – and if they are possible I’ve never met a buyer willing to wait for the perfect conditions or who has the additional money it would take to make the conditions perfect. On the subject of “fill dirt", this is soil that is brought in to a construction site when there's not enough soil already present to complete the project. A simple rule of thumb is to think of fill dirt as the opposite of virgin soil. If the soil in question has been moved whatsoever (from one lot to another or within the lot), it is fill soil and not structurally sound for building on without taking additional measures. The reason it’s not sound is essentially because the soil is no longer compacted. You can imagine what would happen if you tried to built a fort in your back yard on top of a dirt pile - after the first rain the fort would sink on one corner or another or maybe just slide down the hill altogether. If you wanted the fort to stay in it's place, you'd have to drill some piers down through all of the fill soil to reach solid virgin soil. Then the fort should be stable. Building on fill dirt will no doubt result in additional construction costs. Even more expensive than building on fill dirt is finding out that you’re building on fill dirt with a lot of rock mixed into the fill. One situation I saw was where the developer had brought in a lot of fill to make existing lay of the land more level so streets could be completed. But not only was the fill not all dirt, it was well more than 50% rock! The story gets better. While the developer should have rejected the fill dirt due to all of the rock included in it, there would have been a problem no matter what because 14 feet of fill had been brought in - which is obviously well more than any 8 or 9 foot basement could have accomodated. If the fill had been strictly dirt then piers could have been installed five or so feet down to reach virgin soil. But because the fill had so much rock in it, piering was not an option. The alternative? Digging out all 14 feet of fill dirt and rock – under the entire base area that would soon be the home – and filling 5 feet of it back in with compactable gravel. That’s a lot of gravel, and it wasn’t even as simple as throwing in 5 feet of gravel and calling it good. The gravel had to be installed in 6-inch layers, and then compacted by a large excavation machine driving over the gravel for hours. Then a soil engineer did compaction tests every 6 inches to verify the gravel was adequately compacted. You can see that many thousands of dollars can be quickly spent. How can a buyer minimize the risk of unknown subsurface conditions that that lay below the beautiful lot there about to purchase? The buyer can do a subsurface “perk” test to see what they’re getting into. There are varying levels of tests that can be done such as an engineering company could get involved with drilling holds deep in the ground to see what’s there. A cheaper alternative may be having an excavator dig a deep hole in the center of the lot to see what’s there – this wouldn’t be as thorough as drilling many holes all around the lot of course, but could provide a buyer a better comfort level in moving forward. The costs associated with perk tests can vary greatly. Although I did stay at a Holiday Inn Express last night, I’m far from an expert on the matter so be sure to contact an engineer if you have concerns about expansive soils, fill soils or concrete issues. I’ve put together the follow list to hopefully assist you in locating someone who can help…
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