Blog: Dmidrilling.com Why is My Contractor Saying Caissons Are Required? When a company makes a decision to build a bridge, tower or especially large, heavy or tall building, most general contractors will say work needs to begin well below the ground. While business owners may instinctively know the requirement will be necessary if sub-ground levels are included in the design, excavation work may also be required in a number of other circumstances. When a contractor says caissons are a must, for example, the recommendation is simply being made to ensure proper foundational support for the above-ground structure. Caissons are supports that are built by digging a hole into the ground with an auger. This hole is reinforced with steel and then filled in with concrete. The idea is to create a stronger foundation than straight building on top of the ground can provide. Like retaining walls that shore up the earth while a basement is being built, caissons are necessary to ensure safety. They are also, however, considered a must in many cases to ensure structure integrity for years down the road by preventing issues with compression or uplift as the true intended structure goes into place. Depending on the depth of the excavation required, dewatering work may also be required to ensure caissons are properly put into place. Finding out a construction project that involves a large above ground feature must begin with an excavation below the earth can be a little disconcerting. This recommendation, however, is made to ensure the final design is strong, solid and meant to withstand the test of time. When contractors recommend caissons, retaining walls or dewatering, they are doing so to protect people and the required structure alike.