The foundations are the fundamental constructive element of support of the buildings. Bad execution of the same, the incorrect choice of the depth of support, an incorrect dimensioning of the same, or its simple deterioration by the passage of time in case of old buildings can suppose severe damages for the rest of the building, even arriving at its collapse in the most severe cases. The HD Foundation Repair experts talk about the most common foundation repair techniques.
SUPERFICIAL UNDERPINNING
This is the most common type of operation. It consists of underpinning a foundation whose support level is superficial with another element that will also have external support. The most common techniques are
Reinforcement by injection
This is the solution used when the support area of the foundation is sufficient, but the foundation is deficient due to deterioration or poor execution.
The technique consists of the pressurized injection of grout or cement mortar. This injection needs communicated spaces to progress, so it is only possible to perform it in foundation massifs of dry masonry, gravels, etc., all of them typical of old buildings. These foundations have a low dosage binder that will be degraded due to the passage of time.
Expansion of the foundation by acting on the contours
This involves enlarging the bearing surface of the footing by working exclusively on the shape so that the floor retains its original depth.
In this technique, the new concrete and the old one must be adhered to entirely so that the whole works as a single piece. This is achieved by careful preparation of the contact surface, the old footing being ground and adequately cleaned, and geometric arrangement. The use of appropriate epoxy resins can also achieve good adhesion. It may also be necessary to introduce reinforcement through the old foundation, stitching it to the new one in some cases.
Expansion of the foundation by acting from below
This consists of constructing a new footing under the existing one with sufficient dimensions for its load. This technique is safer and easier to apply in-wall foundations than in column footings. However, HD Foundation Repair professionals must take special care with this technique when loading the new foundation, as the settlement may occur and cause cracks in the building.
This action requires, in any case, the total unloading of the foundation and to carry out the operation by points or zones of action, which must be defined in the execution project.
Extension of the foundation by improving the ground
This method consists of converting the existing land under the foundation into a more resistant material with a larger dimension in the plan. This is achieved by acting from the outside through the pressurized injection of fluids spread over the ground and subsequently forming a compact and resistant material.
Replacement of the footings
On many occasions, it is not viable neither the reinforcement nor the extension of the existing foundation, for what it is necessary to choose to construct a new foundation that replaces it, conserving or not the existing foundation, and never counting on its collaboration.
In this technique, it will be necessary to unload the foundation element using shoring.
It is valid both for intervention on spread footings and isolated footings. However, in the latter case, the intervention is highly compromised, and the shoring of the element on which it acts must be total.
DEEP UNDERPINNING
When the surface pavement does not meet the foundation’s needs, the loads are transferred to deeper, more resistant layers.
There are three types of deep underpinning operations possible:
- First, underpinning using shafts (only suitable for load-bearing wall foundations).
- They are underpinning by piles surrounding the foundation.
- They are underpinning using micropiles passing through the foundation.
Choosing one or the other type of foundation rehabilitation intervention will depend on the designer’s criteria or the project manager. However, micro piles have recently gained a lot of presence in urban rehabilitation, where the space to work with is reduced.
