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Can I Build an Extension Over a Drain?

As a homeowner or property developer, the thought of extending your property can be an exciting prospect. Perhaps you want to add a new kitchen, create a larger living space, or build a whole new room to increase the value of your property. However, there are several considerations you need to take into account before you start, one of which is the presence of drains on your property. So, can you build an extension over a drain? The answer is not straightforward, and several factors come into play.

Understanding Building Regulations

In the UK, the construction of new buildings or extensions over or near existing drains is subject to strict building regulations. These regulations are intended to ensure that the work is carried out safely, to protect the environment, and to prevent any potential problems in the future. It’s essential to consult with a professional surveyor or builder before you start any work to ensure you are complying with all the relevant rules and regulations.

Types of Drains

There are two main types of drains you might encounter on your property: private drains and public sewers. Private drains are the responsibility of the property owner, while public sewers are maintained by the local water and sewage company.

Building over a private drain is generally easier, but still requires careful consideration and adherence to building regulations. Building over a public sewer, on the other hand, usually requires permission from the local water and sewage company, and may involve additional costs and restrictions.

Factors to Consider

When planning an extension over a drain, several factors need to be considered:

  1. Access: The drain should remain accessible for maintenance, repairs, or replacements. You might need to install inspection chambers or manholes to provide easy access.
  2. Protection: The drain should be protected from the weight of the extension. This may involve using special materials or construction methods to ensure that the drain isn’t damaged during construction or over time.
  3. Diversion: In some cases, it may be necessary to divert the drain around the extension, especially if it’s a public sewer. This can be a complicated process, involving negotiations with the local water and sewage company, and may involve additional costs.
  4. Impact: Consider the potential impact of the extension on the drain. For example, an extension could increase the amount of water flowing into the drain, leading to potential issues such as flooding or blockages.


Building an extension over a drain can be a complex process, and it’s essential to seek professional advice before you start any work. With careful planning and adherence to building regulations, it’s possible to build an extension that’s safe, functional, and adds value to your property. If you have any doubts or need further advice, contact a reputable UK drain company to ensure your project goes smoothly and safely.

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