Subsidence Underpinning Services & Solutions
What is underpinning?
Underpinning is the process of strengthening the foundation of an existing building or other structure and involves extending the foundation depth or distributing the load across a greater area. Underpinning is a major subsidence repair technique and in order to choose the correct method, it is necessary to understand the current situation and problems concerning the entire foundation.
Free site assessment: If you have a property that requires underpinning, contact Geobear for a Free Site Assessment that we can now complete via a video call.
Why is underpinning necessary?
There are a variety of reasons why underpinning might need to be carried out. These are usually related to subsidence issues. Some examples of why underpinning might be necessary are:
- A change in soil conditions under the foundation
- Soil characteristics were not properly taken into account during the design phase
- The original foundation is no longer suitable/strong enough
- The construction/repair/excavation of neighbouring structures endangers the current foundations
- Additional floors are to be constructed underground
What Are the Different Types of Underpinning?
There are a few different methods of underpinning that are commonly used to underpin a house or any other type of building.
Mass concrete underpinning
A traditional method of underpinning is soil replacement under the foundations by digging, followed by concrete pouring. The soil is often replaced in box-shaped parts in a predetermined sequence so that the bearing capacity of the current foundation is not compromised. The result is a foundation built underneath the existing one. This method can be used for relatively shallow foundations, and the current structure needs to have sufficient strength to span over the box-shaped underpinning pits.
A piled underpinning is generally used when firm soil layers are situated at substantial depths and the superficial soil is inadequate to bear the loads. Other influential factors favouring piling may be limited access to the construction site, environmental concerns regarding excavated soil or minimal structural movements during the underpinning process. The piles are usually steel-cased and can be filled with concrete. The pile foundations may be divided into three categories by installation technique: driven piles, drilled piles and jacked piles. Piling methods require load transfer structures to transfer loads from the existing foundations to the piles.
The creation of geometry of grouted soil by using a high-velocity jet of cement grout (with or without water/air) is called jet grouting. Regarding underpinning, jet grouting is typically used to create columns of grouted soil underneath an existing foundation. The end result depends on soil characteristics, especially erodibility, but generally, jet grouting is effective across a wide range of soil types. Load transfer structures are not needed, because in many cases the columns can be extended to the existing foundation. Because of the required drilling and high pressure used, jet grouting always causes a soil disturbance, and may not be viable for very sensitive foundations. The construction site must also be accessible to heavy equipment.
This is the super-fast alternative to underpinning invented by Geobear. Over 40 years, geopolymers have been used for a number of geotechnical applications, such as soil stabilisation and re-levelling of floors, compaction of granular soils or increasing the bearing capacity of foundation soils for existing structures. Geopolymers are based on multi-component structural, expanding resins and they are environmentally neutral and water-resistant. The technique is based on chemical expansion pressure, instead of heavy pressurised hydraulic systems, which makes the application more controllable and safe. Most of the projects can be completed in days in cases where traditional ground improvement and repair methods would require weeks or even months to finish.
Geobear provide a free site assessment and proposal to repair your home – Contact us today or call 0800 084 3503
Unlike traditional underpinning techniques, geopolymer solutions are excavation free, utilising small and light installation machinery, resulting in fast and non-disruptive solutions for commercial, industrial, residential and public buildings, as well as infrastructure and historic structures.
What Are the Problems with Traditional Underpinning?
The main problem with many types of underpinning is the length of time it takes and the mess it creates in and around a home. It requires excavation and digging beneath the property, which can be highly disruptive to your day to day life. Compared with Geobear’s geopolymer method, which only takes 1-2 days, old style underpinning is becoming the last resort for property owners.
If you do choose a traditional underpinning solution there are some questions that it is worth checking with your builder or contractor such as:
- Have you the site investigation data to diagnose the problem and the necessary level of information for the solution to be designed?
- Loads of the building should be assessed so that the loads on the underpinning works are catered for in the design.
- Do CDM Regulations apply?
- Are the contractors competent and have accreditations?
- Do they have adequate resources?
- If the site is mini-piled underpinning, will ground conditions be conducive to mini-piling?
- Will access be available for mini-piling equipment (if a piling route is chosen)
- Underpinning contractors generally execute their own design, do they have public indemnity or other insurances and are they financially stable so you are sure they can complete the work?
- Will the building contractor be able to deal with the complexity of the project?
- Have the necessary notices been served in respect of building control?
How Geobear Can Help
With the Geobear alternative to foundation underpinning, there is no reason to leave a property and there is absolutely no excavation or digging – we just need a way to get our material beneath existing foundations, which requires drilling a pattern of small holes around the affected area. At Geobear, we have been working in the UK for over 30 years on 10,000 properties using our ground injection method as a more convenient alternative to those traditional methods.
Contact Geobear Today
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