Can a conservatory be built over a drain?

Simon Edward • 7 February 2025

What happens if you want to build a conservatory over a public drain? Get the answers in our guide.

What happens if you want to build a conservatory over a public drain? Get the answers in our guide.

Getting a conservatory installed is a great way of expanding the potential of your home.


Of course, a well-built, well-maintained conservatory is a pleasant place to be in pretty much any environment. But it can also blend with your home's aesthetic, add to its market value and maximise its floor space.


So far, so good. But what if you want to build a conservatory over a drain?


This introduces two complications. First, building a conservatory over a drain, or even in close proximity, can damage the pipes running nearby. Secondly, water authorities need access to drains. Your conservatory could make that impossible.


For this reason, there are some steps you should take before getting the builders in. We hope this article helps you figure out the best way to proceed.


Rules and regulations


Your home, your rules? Not so fast. Public drains belong to the water and sewage companies, so building a conservatory on top of them creates a conflict of interest.


The key consideration is whether your proposed extension will be within three metres of a public drain. If it is, you need to get in touch with your local sewerage company. You can find your local supplier on the
Water UK website.


They will assess the risk that your conservatory poses to the pipes. If they consider it major, you should look for another location. If, however, they think the risk is negligible, you get the green light to go ahead and start installing your conservatory.


It's also important to note that you can't build over a manhole. These always need to be accessible for maintenance, regardless of whether they're sealed or not.


What happens when you get the green light?


So, you've sought and gained approval for construction from the water company. Before you go any further, you need to plan carefully to ensure the drain in question can be accessed for maintenance and repair.


Picture of a drain on a residential property.

In this situation, there are a number of things to take into consideration. 


Technical considerations


First, there's the foundation of the conservatory. If the drains are shallow or the conservatory will affect the lower end of the drain pipe, you may need to dig deeper foundations.


Your foundations should also be built in such a way that they don't shift over time. This can put unwanted pressure on the drainage system.


This also applies to the building materials you use. You will need to use high-quality materials that won't damage the drain and will distribute the weight efficiently.


The roof, too, needs consideration. You may want to add cavity trays and flashings where the roof meets the wall of your house. Otherwise, you could be looking at leakages.


Finally, you will need to ensure that access is available for maintenance. This could mean installing access points.


It's a lot to think about – and your priority should be getting expert advice from your conservatory installer. They will be able to recommend the right materials and install the conservatory in such a way that it doesn't block or damage the drainage system.


What to look for in an installer


If you get permission to build a conservatory over a drain, your best bet is to get advice from an experienced installer. They will have the skills and expertise you need to ensure a safe, stable, fit-for-purpose installation.


As well as looking for positive online reviews and listening to word of mouth, you should also check that the company is properly licensed, insured and accredited. These objective standards help give you peace of mind that you're working with the right firm.


The right installer can be the difference between the conservatory of your dreams and a logistical nightmare. Make sure to shop around before you sign on the dotted line.


An exception to the rule(s and regulations)


Building a conservatory over a public drain is a problem precisely because the drain is public and the water company may need access.


Picture of water technicians working on a drain.

If, however, the sewer is private and not connected to the public system, you don't need to seek approval.


Even if this applies, you should think carefully before beginning construction as you don't want to damage the pipes or block access.


What happens if you don't get approval?


If you don't get approval from your water company, you shouldn't build your conservatory. This is because the water company need access to the drains.


If you decide to go ahead regardless, you may find yourself in conflict with the water company. They will reserve the right to remove the conservatory to gain access. Fighting this will take a lot of time, energy and money.


On balance, it's rarely worth building a conservatory over a drain without proper permission and proper planning. With any luck, you should be able to get your conservatory installed elsewhere on your property.


Can I build my conservatory over a manhole?


You can't build a conservatory over a manhole as it needs to be accessible to the water company. However, if you get approval, you may be able to relocate the manhole. There are also systems available that install removable access panels.


Do I need planning permission for a conservatory?


Most of the time, you
don't need planning permission to build a conservatory on your property. There are, however, exceptions. These relate to the size and position of the proposed extension, as well as rules regarding designated areas and listed buildings.


Even if nothing stands out to you as unusual about your planned conservatory, it's worth checking to avoid disappointment. If you break the rules, you could be asked to retrospectively apply for planning permission, remove the extension or even pay a fine.


Are you looking for a
conservatory company near you? Calder Windows has been installing high-quality conservatories in Yorkshire for more than three decades. Get in touch today for a quick, competitive quote.


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