Quick Enquiry Call Us


If you cant find what you’re after please don’t hesitate to contact us.

Select Region

Please select the global region website you'd like to view.


Quick Enquiry

Submit your enquiry using our online form and include a brief message about the type of issues you are experiencing. One of the Mainmark experts will contact you as soon as possible.

Privacy Policy(Required)
Receive Information
This field is for validation purposes and should be left unchanged.


Extension subsidence

Are you concerned about extension subsidence in your home?

Extension subsidence is a problem that should not be ignored. If you suspect your home is experiencing subsidence, it’s important to consult with professionals right away to prevent further damage.

Extension subsidence typically occurs due to problems with the soil under your home’s foundations. As experts in dealing with subsidence in residential homes, Mainmark offers solutions that deal with the root cause of the extension subsidence, getting your home back to normal as soon as possible. 

Common causes of extension subsidence include:

  • Inadequate foundation – If an extension’s foundation is not properly designed or constructed
  • Shrinkage or erosion of soil – Often caused by flooding or prolonged dry spells, which cause soil to lose moisture
  • Historic land use – Such as mining or fracking

Mainmark’s extension subsidence solutions, Teretek® resin injection technology, and JOG computer-controlled grouting, are quick, reliable and cost-effective. Work can usually be completed in about a day, causing minimal disruption to your family and allowing you to rest assured that your extension is safe, stable and on solid ground.

The signs of extension subsidence

If left untreated, the problems associated with extension subsidence can become exacerbated, causing more damage, and possibly requiring the extension to be demolished or rebuilt. Knowing the signs of extension subsidence can help you spot problems early and get help before further complications arise.

A common sign of extension subsidence is the noticeable separation between the extension and the main house structure. This will appear as cracks in the internal or external walls where the extension meets the house. As well as being a clear sign of extension subsidence, this separation can be a safety hazard, it can cause draughts and it may allow rainwater and other moisture to get into your walls.

Other potential signs of extension subsidence include:

  • Cracks in walls, floors or ceilings
  • Doors and windows that stick or don’t close properly
  • Sloped, sinking or otherwise uneven floors
  • Unexplained ripples or creases in wallpaper
  • Leaning of the extension

By recognising these signs and taking prompt action, you can mitigate the impact of extension subsidence, ensuring the safety of your home and preventing more extensive damage in the future.


Technologies for treatment of extensions subsidence

Teretek® resin injection for extension subsidence treatment

Teretek® is an engineered solution for re-levelling subsided residential homes and treatment of extension subsidence, using a plural component, expanding polyurethane resin. Teretek® works in a way similar to keyhole surgery. Small holes are drilled under the foundation in order for Mainmark’s proprietary, environmentally inert resin to be injected under the house foundation, improving the stability of the ground and re-levelling the home.

Teretek® resin injection technology

JOG computer-controlled grouting for extension subsidence

JOG computer-controlled grouting is a multi-point injection technique that can be used to remedy extension subsidence in residential homes. This technology typically uses cementitious grout to re-level structures, including residential homes and extensions. This means that cementitious grout is injected under the foundations of your home, using computers to accurately control the injection amounts in the various predetermined locations.

JOG computer-controlled grouting

We’re happy to have helped

Mainmark technology benefits

Benefits of Mainmark’s treatments for extension subsidence


Our technologies are installed quickly and can be walked on soon after.

Environmentally inert

We use safe materials that are non-toxic and do not leach into the environment or affect the treated area.


Our solutions are surgical in nature, causing minimal disruption to you and your family.


Compared to other solutions, our technologies cost significantly less and have fewer associated costs.

Soil stabilisation FAQ’s
What happens with unlevel driveways, floors and hardstand areas?

After the application of the Mainmark solution, unlevel surfaces will become aligned again as the ground underneath is strengthened and re-supported. Simple cosmetic repairs may be required.

Will there be a mess?

Very little, if any. We use Teretek® engineered Resin Injection technology, which is likened to “keyhole surgery”, or JOG Computer-Controlled Grouting, with no major excavation and minimal disruption or mess. The injection holes required are very small.

How long does it take?

Each project is different and depends on the required amount of lift, area for correction, building construction, and ground conditions. Most projects can be completed in a day or two, and we can work at night or on one area at a time, so your business can keep operating.

Do i need to send my workers home?

No, most projects don’t require you to vacate the premises or even move furniture or equipment. For the most part, you can keep operating as normal. Driveways can often be driven on in as little as 30 minutes after treatment.

What warranty will i get?

The materials we use have been developed for use underground and have been specifically engineered to resist shrinkage and deterioration. Teretek® is warranted by Mainmark for an industry-leading period of 50 years.

Is it safe and environmentally friendly?

Injected Teretek® and JOG materials are environmentally inert and have no detrimental effects on the environment.

Get a quote

Arrange a site assessment in three simple steps:

Step 1

Submit your enquiry using our online form. Include a brief message about the type of foundation issues you are experiencing.

Step 2

Our friendly customer service team will be in touch to schedule a site assessment that suits you.

Step 3

One of Mainmark’s experts will visit your home or property, assess the damage and determine the likely cause. They will establish the approach needed, create a plan specific to the needs of your building and provide you with a detailed quote.

Privacy Policy(Required)
Receive Information
This field is for validation purposes and should be left unchanged.

© 2024 The Mainmark group of companies. ‘Mainmark®’, ‘Terefil®’, ‘Terefirm®’ and ‘Teretek®’ are trademarks of the Mainmark group of companies.

Mainmark Ground Engineering (UK) Ltd.

CRN: 09372443

Ground Improvement



Subsidence Repair

About Mainmark

Our team




Media & Press



Privacy Policy

Terms and Conditions

Created by Codex