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Help! My Neighbour Is Building a Basement

Defending Your Property: What to Do When Your Neighbour Builds a Basement.

Article By: Tom Ayre
Last Update: January 2023

If you have a neighbour who plans to build a basement, you may be concerned about the potential impact on your home and neighbourhood. The process of building a basement can be quite lengthy and involve significant excavation and construction work. This can cause disruption and noise, as well as the presence of heavy machinery and delivery trucks. In addition, living next to a construction site can be stressful, as contractors may need to access your property and there may be constant noise and activity throughout the day.

Despite these challenges, basements can be a great way to add additional space to a property. Many homes in London have undergone or are undergoing basement construction, and these projects can involve digging down as many as three floors. If you are faced with a neighbour who is planning to build a basement, there are steps you can take to protect your property and minimize the disruption during the construction process. In this article, we will discuss what you can do before and during a basement building project to help manage the impact on your home and neighbourhood.

Table of Contents

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THS Concepts undertakes monitoring surveys across London & the South East. We work for insurers, surveyors and structural engineers providing detailed reports on building movement.

How Are Basements Built?

There are several ways to build a basement, and the specific method used may depend on factors such as the location and soil conditions of the site, the size and shape of the basement, and the intended use of the space. Here are the main steps involved in building a basement:

  1. Excavation: The first step in building a basement is to excavate the area where the basement will be located. This involves removing soil and other materials to create a hole large enough to accommodate the basement. The excavation process may also involve grading the site to ensure proper drainage and stability.

  2. Footings and foundation: After the excavation is complete, the next step is to pour concrete footings and foundation walls. The footings are typically located below the frost line to prevent the foundation from shifting due to freezing and thawing. The foundation walls are typically made of concrete, and they support the weight of the house and help to transfer it to the ground.

  3. Waterproofing: To protect the basement from water infiltration, it is important to apply a waterproofing membrane to the exterior of the foundation walls. This may involve applying a layer of waterproofing material, such as rubber or plastic sheeting, or applying a liquid waterproofing compound.

  4. Framing: After the foundation is complete, the next step is to frame the basement walls, floors, and ceiling. This typically involves installing wood or steel framing members, which will support the finishes and other materials that will be applied later.

  5. Finishes: Once the framing is complete, the next step is to add finishes to the basement, such as drywall, paint, flooring, and electrical and plumbing systems. This may also involve installing windows and doors, as well as any other features or fixtures that are needed.

Overall, building a basement involves several steps, including excavation, pouring the foundation and footings, waterproofing the walls, framing the space, and adding finishes.

Basements In Terraced Houses

When digging / underpinning on a terraced block of houses it is common for properties to share foundations and structural walls (party walls). It is the details surrounding the foundations that will need thorough investigation by the Structural Engineer / Party Wall Surveyor. 

During construction it is these foundations that will need to be underpinned, adjusted or added to. With the extensive amount of work that has to be undertaken with digging out and forming a basement it is no surprise that there can be problems. Common issues range from minor cracking where at best you may have a few minor cracks in the walls to the (very rare) major structural failure!

What Can You Do Before Building Works Begin

Firstly, speak to your neighbours and discuss the works with them. If your neighbour is friendly then they should be happy to explain the process of the works and time frames.

It’s also a good idea to have a look at your local council’s online planning portal. You can type in your neighbour’s address and view/download their plans and planning application document.

Your neighbour should have a Party Wall Surveyor who you can ask questions about the works. If you are particularly worried it may be prudent to appoint or take advice from your own, independent Party Wall Surveyor (we recommend Congreave Horner if you’re in the South East!). The Party Wall Act 1996 ensures that there must be an agreement between you and your neighbour regarding the works.

You may want to also want to consider asking your neighbour to appoint a monitoring survey company, like THS Concepts, to install fixed targets to their and your property. The purpose of the survey will be to observe these fixed points on a regular basis. Your monitoring survey company will be able to report back and advise if a point has moved up, down, left or right. This will in turn indicate if there is a structural weakness in the wall.

THS Concepts undertake monitoring surveys on a range of different projects across London and the South East. Following each job we issue our clients with a detailed report showing movement of points to within 1mm!

Carrying out a monitoring survey can be a key piece of evidence in neighbourly disputes by illustrating clearly that something has moved. A common problem occurs when residents have complained about building movement, but there are no base records to suggest what the building movement was prior to the works being undertaken. This can weaken an argument as it can’t be proven that construction was the cause of new movement!

At least 1 month’s notice must be given to you if your neighbours are building a basement. You must ensure you have received notice as it should outline the proposed methodology and details of what they are planning to do.

Another good idea is to take lots of photos of your property focusing on the area/wall the works are going to be taken next to. A photographic record can help demonstrate locations that have been damaged as a result of the works. Doing this prior to the works being undertaken and safely storing these away is important. Make sure your photos are clear, extensive and are taken with good lighting.

Monitoring Your Neighbour’s Building Throughout Construction

It can be a good idea to introduce yourself to the building contractor undertaking the task of digging out and forming the new slab; a bit of dialogue with the contractor can sometimes put your mind at ease. If you get a contact telephone number from them you can also get in touch if to discuss issues such as loud noises before or after social hours, workers parking on the road, contractors smoking outside your property etc.

Should you find that the work is causing you and your property problems, then keep a diary. The diary should be updated with dates and times as to when things are occurring. Take plenty of photos of damage and areas you aren’t happy about. You can then keep your Party Wall Surveyor up to date. Keeping good records is important as if a claim does arise then these will be vital evidence to support it.

If you have noticed structural damage to your property, then it is important that you notify your neighbour and advise on the problem. If the issue is serious, they may have to pause works on site whilst this issue is rectified or re-planned.

If there is a monitoring survey being undertaken during the works, then it would be a good idea to have the regular results sent to you as well. This way you can keep a detailed eye on the movement within theirs and your property.


  • Speak to a Party Wall Surveyor and let them know the situation. 
  • Speak to your neighbour / their builder and ask them to explain the build.
  • Engage with a structural monitoring company such as THS Concepts
  • Keep records, take photos and record details about your property prior to works.

Keeping things friendly with your neighbour is important. A regular dialogue between you, your neighbour and their contractor can really help put your mind at rest. Sometimes a quick conversation can solve many problems on the spot.

Prior to the works being undertaken it is important that you record, photo and document and area you feel may be affected. Store these away safely on your computer and back them up so you don’t lose them! Construction jobs can last many years so safely filing them away where they can be retrieved is important.

During the works you need to be keeping an eye on your property. If you have any problems, then document and report them to your neighbour. Keeping things civil is crucial. Losing communication and general nastiness can cause problems with tit for tat claims and often results in negativity for both parties!