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Bay window subsidence

How to deal with bay window subsidence

If you suspect bay window subsidence is affecting your home, it’s important to get expert advice as soon as possible. Subsidence can lead to serious damage to your home, and dealing with it quickly will prevent the problem from getting worse. 

Mainmark offers swift, non-invasive and reliable solutions for bay window subsidence. Our Teretek® resin injection technology and JOG computer-controlled grouting deal with the root cause of subsidence, helping return the charm and beauty to your bay window with minimal disruption.

As alternatives to mechanical jacking, underpinning and piling, our methods use surgical-like precision and address subsidence under your bay window. Our solutions can:

  • Improve the ground – Our methods effectively increase the load-bearing capacity of the ground
  • Lift and re-level – Injecting these materials under the foundations of your bay window will gently lift the entire structure and return it to level.
  • Fill in voids – This ensures stronger and more even support for the foundation.

Why is bay window subsidence a problem?

Bay windows are a charming architectural feature, but bay window subsidence can compromise the window’s integrity, affect your home’s aesthetics and be a safety hazard. Bay window subsidence occurs when the structure begins to sink, settle or shift. Poor foundation construction is one common cause of bay window subsidence in residential homes. This is due to a historical misconception that bay windows were lighter than other parts of a house; therefore, they were built with lighter foundations. Other possible causes of bay window subsidence can include:

  • Soil issues, such as erosion or shrinking caused by droughts or flooding
  • Nearby heavy traffic can create underground vibrations that affect the soil
  • Historic mining activities or fracking

Signs of bay window subsidence include cracks in the walls, floors, or window frames, as well as uneven window alignment, difficulty opening and closing windows and gaps between the bay window and the main structure.

If you notice any signs of bay window subsidence, the best course of action is to have your window checked by a specialist who can diagnose the problem and advise on the right solution for your home.


Technologies for dealing with bay window subsidence

Teretek® – resin injection for treatment of bay window subsidence

Teretek® is an engineered solution for re-levelling subsided residential homes that can be used to treat bay window 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 treatment of bay window subsidence

JOG computer-controlled grouting is a multi-point injection technique. This technology typically uses cementitious grout to re-level structures, including residential homes. It can be used to effectively treat bay window subsidence as the 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

Mainmark technology benefits

Benefits of Mainmark’s treatments for bay window 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.


We’re happy to have helped

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.

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Mainmark Ground Engineering (UK) Ltd.

CRN: 09372443

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