There are many reasons that a homeowner may want to strengthen their home's existing foundations with underpinning -- they may be guarding their foundations against potential damage caused by changing soil conditions or flooding, or reinforcing already damaged foundations during the process of foundation repair. However, no two foundation strengthening projects are ever identical, and there is a number of underpinning methods to choose from.

Two of these underpinning methods are more commonly used than the others, which are generally highly specialised methods suited to very specific scenarios. Mass concrete undepinning and beam and base underpinning, on the other hand, are highly versatile methods that can be used to strengthen almost any foundation. Each of these methods comes with its own advantages and disadvantages, so be sure to familiarise yourself with them and consult closely with your chosen underpinning service before deciding on a method.

Mass concrete underpinning

This simple and venerable underpinning method has been used for decades, but remains effective today. A comparatively simple process, mass concrete underpinning involves digging chambers in the soil beneath your existing foundations, before filling these chambers in sequential order with poured concrete.

This measured application of concrete prevents excessive shifting as the concrete sets and cures, minimising the chances of any structural damage being dealt to your home. However, this simple method also has other advantages: it is relatively inexpensive, does not require large amounts of heavy excavating equipment, and can be performed even if access to your home's foundations is obstructed.

However, mass concrete underpinning is generally limited in effectiveness beyond a certain depth, and may not be suitable for reinforcing particularly deep foundations. The need to transport large amounts of concrete to your property can also churn up your ground, especially during wet weather.

Beam and base underpinning

This method is essentially a more modern refinement of mass concrete underpinning; instead of simply pouring concrete into pre-dug chambers, the chambers are first propped and reinforced with robust steel piles, which effectively deepen your foundations and take excessive loads away from vital areas. These piles are then surrounded with a network of reinforcing steel beams, and the whole arrangement is covered with concrete as the chamber is filled in.

This sophisticated underpinning method is particularly well suited for reinforcing the foundations of heavy buildings, as the addition of steel beams makes beam and base underpinnings enormously strong. They are also particularly well suited to foundations damaged by shifting soils, as anti-heave materials can be inserted around the underpinnings to guard against soil expansion and contraction.

Unfortunately, the increased complexity of this method generally increases its cost, although the work can generally be carried out more quickly. Installing such an extensive network of reinforcing beans can also cause disruption to your sewage and draining systems, and you may have to vacate your home for a brief period.