What does underpinning a house mean? 

Underpinning is an engineering method used to strengthen and improve the foundations of a property. This technique is usually required when the original foundations become weak and are no longer strong enough to support the weight of the structure. Factors such as soil movement and subsidence are common causes of unstable foundations.  

Why might your house need underpinning? 

Over time, the ground beneath the property can shift, causing the structure above to become unsupported and potentially subside. Underpinning methods strengthen the foundations, ensuring the house is re-levelled and supported. Your home may need underpinning if you notice any of the common signs of subsidence such as cracks in walls, sticking doors or windows and sloping or uneven floors. 

Types of underpinning 

When it comes to resolving subsidence issues, there are different methods of underpinning available. The chosen method typically depends on the scale and severity of the damage.

Mass concrete 

Mass concrete underpinning is a traditional method that involves excavating sections below the foundations of a building and filling each void with concrete. Traditional underpinning methods dating back to the 15th century, it remains the most widespread underpinning method. 

Piled 

This method involves removing the internal floors of a property and installing a grid of steel-cased piles, which is then filled with concrete. Piled underpinning is typically used to transfer a foundation load to more stable soils at deeper depths, as the previous soil is too weak to bear the weight of the building. 

Computer-controlled grouting 

This method involves using an array of injection ports to inject high-mobility grout into the ground, under precise computer control. This non-invasive method gently raises the structure (by up to 300mm) and can be used for a range of applications from residential homes to large commercial buildings. 

Resin injection 

Resin injection involves injecting resin through small holes to fill voids, improving soils and increasing the load’s ground bearing capacity. This modern method doesn’t require digging or excavation.  

For example, Teretek® resin injection was used to improve the foundations of a terraced home in North Dublin. Leaking clay drainage pipes had weakened the ground beneath the property and had to be repaired. Following these repairs, resin injection provided a non-invasive, effective solution, completing ground strengthening in two days. 

Will underpinning affect your home’s value? 

Although subsidence can affect the value of your home, underpinning can help to mitigate this because it confirms the property is now supported. It’s worth noting, however, that some building insurance providers may charge higher premiums for properties that have experienced subsidence.  

Some buyers may also be reluctant to purchase a property with history of subsidence, and mortgage lenders may not approve financing unless proof of repairs has been made. Typically, buyers and insurers will want to see a Certificate of Structural Adequacy (COSA), a report from a qualified engineer, or a completion certificate to prove that the building is structurally sound.  

Mainmark expertise 

Mainmark Ireland offers a range of reliable ground improvement technologies that can support your home, safely and quickly. Our underpinning alternative technologies are non-invasive, compared to traditional underpinning solutions, which means in many cases occupants don’t need to leave the property while work is taking place. Additionally, works can often be finished in a day. 

Although subsidence is concerning, understanding more about underpinning and how it can help remedy the issue, is key to protecting your home both structurally and financially in the long-term.  

If you have concerns about your foundations, get in touch with our experts today.