Basement Excavation Contractor – St. George, Utah
Here in St George, many homeowners prefer to add on basements. The added square footage and the excellent insulation from our hot summer months provide added value and cool escapes for families throughout Southern Utah.
If you are like most of the homeowners who ask us what is involved with digging a basement then you too might be a little surprised to learn there is quite a bit of preparation, skill and even engineering that goes into digging out a basement.
Did you know that the overall finished height of your home and sometimes even the dimensions of your basement may be affected by one or more of the following:
- Considering Utility Elevations
- Soils Testing – Composition and Compaction
- Excavation and Planning
Considering Utility Elevations
When digging or excavating a basement it is important to consider the elevation of the existing sewer lines. If the house is set too deep and the finished grade of the basement is too low then a sewer pump might be needed in order to get the waste out of the home. Given the additional cost and the long term maintenance of sewer pumps, it is usually better to bring up the grade of the home rather than installing a sewage pump, but in some cases it might not be possible any other way.
When figuring out how deep we need to dig for the height of the basement walls, we need to take into account the existing elevation of the lateral sewer line coming in from the city or county and the distance from it. From there we determine how low the finished grade of the home can be while still offering the appropriate drainage for the sewer lines. If the overall height of the home needs to be raised, we simply dig a hole that is more shallow and use the excavated earth as back fill around the home.
Building Lot Topography
Another important element to consider is the drainage of the lot and this is determined in large part by the topography of the lot. This is especially true here in Southern Utah where we can get flash floods (usually during the months of June through August). A lot of people who relocate to the desert, specifically here in Southern Utah are surprised to learn that flooding can be a problem in the desert. When the monsoons season comes, a basement can turn into swimming pool in minutes if the appropriate drainage is not planned for.
Soils Testing – Composition and Compaction
Caliche soil (also known as blue clay) is something you definitely don’t want. If you have been around St. George for a while then you know that several decades back blue clay was causing a lot of people a lot of problems. The problem with blue clay is that it swells when it gets moist. If you have a lot of it under your house, under your footings, it can actually raise that portion of the footings causing cracks and damage. The inverse is that if you build on the clay when it is swollen and it dries it will actually collapse equal to the amount of swelling. That is why it is so important to get a soil report done by a soil engineer before you purchase your lot or before you begin construction. On average, a soil test will cost about $500, which is money well spent. A soil engineer will come out to the lot and check for the density (compaction) of the soil and the actual soil composition.
One of the only solutions to the blue clay problem is to over excavate until you don’t find any more (up to 14 feet) and then bring back the right kind of fill in lifts (usually every 12 inches) and compact that new soil properly. As you might guess, digging out 14 feet of dirt, hauling it away, bringing in new good material, and compacting it every foot can get expensive. The soil engineer will come out and test the soil at very bottom of the hole after we’ve dug it out, just to make sure that we don’t need to go any deeper. Then they will test every 2 feet on when we are bringing in new materials and compacting it in lifts. So if in the case of a 14 foot blue clay over excavation, the engineer will test it at 7 different lifts and usually you’ll do it 3 or 4 times per lift. They test it in different spots of the home. The 14 foot example is not as common (maybe 3% – 5%), but we see quite a lot of 4 – 6 foot over excavation (maybe 30% – 40%). So it really pays to make sure if you are looking at putting in an offer on a building lot, make it contingent on the soil test report. In some cases the costs of over excavation, like in the 14 foot example it can be between $30,000 and $50,000.
On properties that have a slope, walkout basements are popular. In this case you will usually need to plan for retention walls to the side, but this will depend on the lot, drainage and choice of materials.
Excavation and Planning
We like to plan out your basement excavation in St. George before we begin digging. We also need to consider if the lot will have a well and/or septic system, but they should be spelled out on the plot plan/blueprint which we will need to have before any excavation begins. We will consider where the spoil pile (the ground removed from the hole) must go and if we are going to need to haul any material away. In some case we may need some of the dirt and material to build access ramps for the equipment and even the concrete trucks, although more and more concrete contractors in St. George are opting to use concrete pumping services.
When excavating a basement, we really don’t want all the dirt removed and stacked on one side of the property. A portion of this dirt has to be backfilled against the basement walls. If there is enough room on site we can slope the extra dirt so that the concrete contractor can have room to walk around or have room to position their stacks of form boards. The amount of room we have on site dictates where we can position the extra dirt and how your concrete contractor can access the site.