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Basement Underpinning for Lowering Floors

Basement Underpinning/Lowering Floors in Virginia

Sometimes Virginia and Maryland homeowners want to lower their basement floors in order to make their basements into additional living space. The method most commonly used for digging a deeper basement is basement underpinning. Underpinning involves digging beneath the footings of the home (concrete that distributes the load of the foundation) and filling in additional concrete. Once complete, the basement floor can be dug deeper without undermining the support of the foundation walls.

Steps for Basement Underpinning/Lowering Floors


underpinning a basementBasement Masters Waterproofing implements the following steps to underpin a residential foundation and lower a basement floor.

  • A series of 4′ wide holes, separated by 8′ of undisturbed soil, is dug beneath the current footings of the home and filled with concrete. The top 2″ of the concrete-filled hole is usually packed with non-shrink grout to avoid air pockets between the bottom of the footing and the top of the underpinning segment.
  • Once the first series of underpinning segments are complete, the adjacent 4′ wide segments are dug-out and filled. This process essentially extends the footing of the home to a lower level.
  • After excavating, we can install steel push piers underneath your foundation. These devices are used to support the weight of the structure and take pressure off of the foundation by anchoring into the soils deep under the surface of the ground. Once the weight of the building is transferred onto the piers, the foundation is lifted to the proper position.
  • After the underpinning process is complete, the concrete floor of the basement is removed, and soil is dug deeper into the basement.
  • When the basement is deep enough, another concrete floor is poured, while the foundation walls of the home are undisturbed.
  • The soil excavated outside of the foundation walls will be replaced so that the home’s exteriors looks the same as it did before.

Things to Consider When Doing a Basement Underpinning Project

inspection and evaluation of your basement underpinningThere are several things that you and Basement Masters Waterproofing will need to take into consideration before completing a basement underpinning project:

  • Make sure that you check the level of the sanitary sewer connection before starting this type of work. If the sewer is higher than your basement floor, then you may have to install a sanitary ejector pump in the basement.
  • Make sure that the underpinning of your foundation doesn’t encroach upon the stable soil which supports your neighbor’s house. (The neighbor’s home may need to be underpinned also.)
  • Make sure that the water table is not too high so that your basement floor is “underwater”. Ideally, the water table should be at least 24” below the bottom of the underpinned wall to maintain adequate soil-bearing capacity.

If you have a  need to lower the floor of your basement, the experts at Basement Masters Waterproofing can help you with all of your basement underpinning excavation needs in the Northern Virginia area. Contact us for a no-cost evaluation!

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