Structural rehabilitation involves the upgrading or changing of a building’s foundation in support of changes in the building’s owners, its use, design goals or regulatory requirements. In every case it is determined that it is cheaper to rehabilitate the structure and make the building improvements instead of demolishing and constructing a new building in the allotted space. Sometimes the existing building has historical characteristics deemed significant where many city, state and national regulations can prevent demolition as a viable property improvement option.
Some of the changes that trigger the need for a structural rehabilitation can be a plan for the addition of new floors above the existing structure, the installation or expansion of an underground parking garage or increasing the size and depth of the elevator shaft enabling it to reach to the basement levels. Also, settling damage where a small shift in the foundation causes cracks in walls and floors can affect the function of the structure such as a pool that suddenly begins to leak through the floor of the pool.
Column needling is the temporary realignment of foundation loads onto temporary beams that allow underpinnings work to proceed without disrupting the displacement of the weight of the supported structure.
As shown in this photograph of the column needling performed at the Bard Hall project, two footings are made at the new (deeper) basement level. This involves digging out the floor and removing rock to the engineer-defined appropriate level. Then the two temporary footings have rebar installed and concrete is poured.
Two horizontal beams that span the interval between the two new footings are welded to the load bearing vertical beam and shim-style inserts prop up the ends of the horizontal beams. This allows the weight of the structure to be safely transferred from the center beam to the two new footings through the horizontal beam.
Underpinning work to extend the footing below the center beam can now progress. This typically involves removing the old footing, rock removal and installing a new steel reinforced footing to the engineer-defined depth. The beam can be extended with new steel or the footing can be built up to the existing end-of-beam level. Once cured and prepared for final installation, the horizontal beams are cut from the load bearing vertical beam and then the horizontal beams and two temporary footings are removed.
Island Foundations Corporation are specialists in structural rehabilitations with complex challenges and or demanding work schedules. We have experience in column needling techniques, rock removal in confined spaces, cement pours in awkward and demanding places and are frequently asked to complete complex assignments on tight schedules.
We invite building owners and general contractors to contact us early in their project development phases so that we can offer our advice based on years of experience to help with budgeting and job scope.