We have put up this step-by-step guide to underpinning to help you decide if your property requires it and what measures you will need to take.
The installation of new, deeper footings beneath an existing house to stabilize it and prevent ongoing or new movement or subsidence is known as underpinning a house foundation. Depending on your situation and why your property is shifting, underpinning might be the ideal solution.
Let’s take a look at what underpinning is and how it might potentially be able to help you with your subsidence problems.
What Is the Basis for?
Underpinning is the process of reinforcing the foundation of a home, a residential residence, or even a commercial structure by constructing new concrete or steel footings to stabilize, reinforce, or raise the existing footings.
In order to support your home on more stable ground than the land it currently rests on, underpinning is a construction technique that involves adding additional footings beside and beneath your home.
Residential underpinning serves the function of supporting your footings on soil that is more solid, stiffer, stronger, and less prone to shift in the future.
When structural engineers recommend underpinning in structures, it is often to sustain a house that has one downward reflection of soil and requires deeper footings in order to prevent potentially dangerous structural movement.
What Is Structural Movement?
It is a reality that all structures move. Many older structures were also built with shallower foundations, which means they move more than modern buildings in response to variables such as seasonal changes in ground conditions or new loadings — especially in areas with clay subsoils.
While structural movement may cause the occasional door or window to stray in its frame, a little forethought may quickly correct such small niggles. So, for calm-headed homeowners, worries about structural movement and underlying expenses may sometimes be used to their advantage by acquiring a deal.
What Causes Subsidence?
Some types of sinking can occur if the earth beneath a portion of the foundation shrinks, removing support from the wall (often caused by leaking drains or lengthy periods of drought aggravated by trees taking moisture). The unsupported portion of the wall directly above might then rapidly descend, producing cracking.
This is in contrast to ‘settlement,’ in which the earth is gradually squeezed over time by the weight imposed by the construction. As the earth adjusts to the increased weight forced on it, all structures settle after construction or in reaction to substantial new structural changes such as expansions and loft conversions.
Surprisingly, the majority of insurance claims for reported subsidence turn out to be cosmetic damage, and the vast majority are denied as invalid since the source is elsewhere, such as differential movement cracks. Almost three-quarters of the legitimate claims are tree-related.
Regardless of the particular source of movement, the main issue to answer in all circumstances is whether the movement is historical or ‘progressive’ and likely to move more in the future.
Subsidence is more common in older homes with shallow foundations on clay subsoil, on slopes, and among trees. Where fractures spread beyond damp-proof course level down to foundations, alarm bells should start to sound – now is the moment to start thinking about underlying expenses and how they may affect your budget. You can contact Watertight Homes as they can perfectly guide you in this regards.
When Should a House Be Underpinned?
Underpinning is a trendy word right now when it comes to resolving home movement issues. Is underpinning, however, the best answer to your house movement problem?
House footings shift for a variety of causes, and not all of them need underpinning.
Underpinning is beneficial when the footings for a home or set of units have sunk or lowered for an unreversible reason. When a footing is built on loose or soft soil (such as unmanaged fill), the movement is unlikely to be reversed.
Underpin footings can be used to strengthen the stability of your house if your house’s footings were not initially put deep enough.
The Downsides of Residential Underpinning
Although widespread advice suggests that underpinning, which entails excavating behind the sunken wall and pumping in massive amounts of concrete, is the solution to subsidence, it is expensive and should only be used as a last option.
This is especially true with older properties since the unsupported portion will continue to move naturally in response to ground conditions, creating pressures with the suddenly rock-solid underpinning length of wall.
Future purchasers and insurers are also scared off by underpinning.
Before you consider underpinning charges, make sure the reason for the sinking has been carefully researched.
How does Concrete Underpinning Work?
Underpinning a home with concrete often entails excavating new bored pier footings beside a house at 2m to 3m centers around the outside of the structure.
Inside the home, concrete foundations are sometimes necessary. The underpin footings must run deep enough into the soil to find a solid adequate foundation to support the weight of the structure.
The deeper footings must then be connected to the existing building. This is frequently accomplished by excavating beneath the existing footing (undermining the footing) to produce a strong support for the current footing.
Each pier and prop configuration is then strengthened with steel reinforcing bars and filled with concrete.
Underpinning contractors that are astute allow enough space between the undergird and the old footing so that once the concrete is solid enough, the underpin may be utilized to jack up the house and level it again.
The jacking operation will occasionally cover up settlement cracks in a home, but because the fractures dislodge unevenly, the fissures will not always close up.
How Long Does it Take to Install Underpinning?
The amount of underpinnings selected by the engineer determines how long the underpinning procedure takes.
The job for a house that requires up to ten underpinnings will take about two weeks.
If your entire house requires underpinning, you might be away from your home for roughly a month.
How to Set Up Underpinning
Most underpinning contractors recommend that a structural engineer evaluate and report on the foundation first. This is due to the need to identify and diagnose footing movement that may reverse due to a change in soil moisture conditions.
Before developing a foundation underpin solution, the structural engineer should advocate independent soil examinations.
The depth, diameter, and spacing of the underpinnings can be specified by the structural engineer depending on the kind of building, the strength of the soil, the type of soil, and the degree of footing movement. Then you will need to hire a contractor to get building approval and install the underpinnings.