Underpinning a Property: Selling a House With Subsidence
Owning a home is everyone’s dream and when it happens it brings joy. However, after owning a home, subsidence is what you don’t want to encounter.
Underpinning is a process that involves correcting properties or structures that have been weakened by subsidence.
It is done to strengthen the existing foundation of a structure.
To strengthen the subsidence structure you start by digging deep into the soil around the property.
The dug place is then replaced with strong construction material with deeper footings to aid the properties structure and stabilize its strength.
Different Types of Underpinning
- Mass concrete underpinnings
This is the most used strategy in underpinning. The process involves deepening the already existing foundation to create new space for new fresh concrete.
- Piling
The use of piles is highly recommended in this process of underpinning. The piles are hard driven into the ground of the subsidence structure.
A stable soil is then added to the piles to support the current weak soil that holds the structure.
- Jet grouting
When the current soil beneath the structure starts to show signs of weakness, grout is added to strengthen it.
This is done using a high-pressure jet that mixes both the existing soil with grout to create a strong base.
You can also inject resin into the ground of the weak soil. A chemical reaction takes place and expands to strengthen the base ground which makes the building level again.
- Beam and base
This involves the support of existing footings by concrete beams. The weight of the structure is moved onto the new concrete beam.
This option is adopted from mass concrete underpinning but it’s more advanced.
- Cantilever needle beam
The process involves an external approach and the work happens outside the property.
The reason why a House Needs Underpinning
When the ground beneath your house shifts and starts to sink, it’s a sign the structure needs underpinning or it will sink and collapse.
Before the property is damaged you will be able to see some signs.
Below are some of the warning signs
- There will be substantial cracks thicker than 2mm which are visible both external and internal
- Torn wallpaper that will start to crinkle on the wall due to wall movement
- Windows and doors will start to stick when opening or closing. The frames also warp due to subsidence
- Large trees around your property have roots that will unsettle the soil beneath the house foundation.
- Clay soil is known to crack and move during dry weather conditions.
- Water leaks that cause saturation and the soil beneath becomes unstable
- The old foundations never used to go deep as the new ones. This makes them too prone to subsidence
How Does Underpinning Devalue a Property?
Underpinning may devalue or increase the value of a property but it will depend on how severe the subsidence was and when it occurred.
Before you buy a house that has a history of subsidence, make sure you get all the needed information about its state before and after subsidence.
Go the extra mile and find out whether the subsidence was dealt with to the fullest and have a complete structural survey.
This will help you know if there’s still the threat of another subsidence and if there’s another threat how big is it.
Up to You
Underpinning will make sure your structural foundation is protected and strongly secured. It also helps you access the mechanics of your house like plumbing which may also require repairs.
Subsidence can also be caused by improper construction of the foundation, wear and tear or even extreme climate conditions.
