Moving a drain for your Extension Project

In this post, we will give you all you need to know about moving a drain for an extension, including what is likely to be involved, and details of the expected costs that will come with the process.

Chances are, moving a drain is probably something you won’t have given much thought to when planning your extension project. You will be thinking about the extra space you will be afforded, as well as all of the added functionalities within, whether you’re thinking of a conservatory, extended kitchen, or any other type of extension possibility.

However, and especially when thinking about an extended kitchen or any other extension taking place outside of your property, you will need to think about the drain. After all, you don’t want an unsightly drain in the middle of your new space, and you don’t want to create any problems that could occur for yourself and your neighbours when renovating near or over it. The drain will have to be placed outside of the area you want your extension built on, but where do you start? Moving a drain is a complicated task, and it isn’t one you should attempt without research and planning.

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Here's What You Need To Expect

Depending on the type of drain you have outside your home, the process to move it could be quite lengthy. It’s not an easy process either, but by knowing what to expect, you will be able to make headway with what needs to be done.

Firstly, think about the task ahead of you. Drains are part of a network that runs deep underground, so any work you attempt yourself could cause drainage issues if you don’t plan ahead.

At the outset, you should check with your local council to see if they have any plans of your house. You can use these as a reference point when planning to move your drain, as the plans should tell you more about the drainage system beneath your property. Of course, these plans could be redundant if the drainage has changed since they were drawn up, so double-check with your council on this.

You might also want to hire a surveyor. While this could be quite expensive, you will at least benefit from up-to-date information about your drainage system. This is also better than lifting up manhole covers yourself and trying to assess the situation with your limited knowledge alone. The average cost of hiring a surveyor is about £250 minimum in the UK, but the price might vary depending on the work that needs to be carried out.

The work required to move your drain is governed by UK building regulations and your local water authority. In the majority of cases, you will need to seek permission to carry out the work from your local water authority before you press on with the job. This is especially true if you intend to build within 3m of your drain or a public sewer, as you need to work according to UK Building Regulation H4.

When speaking to the local water authority, find out what type of drain you have. It might be connected to multiple properties, so there will be building regulations in place that need to be adhered to. A building inspector will be able to tell you more, although there will be a fee attached when calling somebody out to inspect your land and property. The cost varies between authority and private building inspectors, so its a good idea to get a quote from a number of different parties.

You will need to apply to the local water authority if you want to move a drain. In some cases, there may be restrictions on the type of work that can be done, so be prepared for this. If you are given the go-ahead, you will have to adhere to the agreement that is drawn up your water authority. They will also charge you an application fee, the cost of which will vary depending on the diameter of your sewer pipe. Typically, the larger the pipe is the higher the fee, but contact them to find out more about the cost you will be expected to pay upon your application.

The Process Of Moving Your Drain

If you don’t know what is involved when moving a drain, don’t do it yourself. You might only end up making up costly mistakes, and that could badly affect your finances. In most cases, it will be sensible to hire a drainage specialist, as they will know what the job entails. The more work that needs to be done, the more they will charge. Typically, you can expect their fee to be around £150 a day. Be sure to research the local drainage specialists in your area, as you don’t want to hire somebody not equipped to do the job. Get in touch with your local council or friends and family members for recommendations.

You might need to hire other tradesmen too, so factor these into the costs. You might need to hire a landscaper or a gardener to restore and repair the land where the drain has been moved from and to, for example, so include these additional tasks when working out the costs involved.

The work involved when making changes to your underground drainage is not an easy task. There is both surface water drainage (the pipes and drains that carry rainwater to the nearest body of water) and foul water drainage (the water that comes from your indoor sinks and appliances to the drain) to consider. Some properties also incorporate greywater systems, which are connected to storage tanks. A drainage specialist will have knowledge of each of these, but you need to take them into account when planning to take on any work yourself.

If taking on work yourself, only do what you can feasibly manage within your own skillset. You might be able to modify your gutters and drainpipes yourself, for example, as you need only fit any new pieces to the existing pieces after finding out the type of drainage system being used at your property. Modifying the underground drains is more difficult, however. You will need to make sure that all drains run downhill and at an angle to avoid nasty smells and blockages. You might also need to implement new junctions and inspection chambers within the drainage system. In instances such as these, you should seek expert assistance as mistakes can easily be made by people without the required expertise.

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The Costs Involved

Your initial cost will be the survey of the drain, and at a minimum, this will be around £250. The price will go up according to how long it takes for the scan to be completed.

You will also be looking at the different materials required for your drain removal. These include the pipes you will need, and the bigger the job involved, the more pipes you will likely need. A basic pipe costs as little as £5 for 1 metre, while higher quality and specific types of piping will cost upwards of around £30 for each pipe.

You will have to factor in the application fee to your local water authority, and more details can be gathered by getting in touch with them.

Then there are labour costs, which could be around £250 per day. The amount you will have to pay will depend on how long the work takes to get done, and how difficult the job is for the drainage specialists and tradesmen you hire for the tasks involved. You are also looking at around £125 for your sewer line to be signed off by a building inspector.

Cost breakdown for a small drain could amount to around £1,000. You’re looking at £750 for tradesmen hire and £250 for materials.

If you need to relocate the drain from the main supply, your costs are going to escalate. At most, you are looking at around £4000. Materials will cost around £2250, the scope and timing of the project will be reflected in the cost of tradesmen hire, roughly £1800, and there will be the added cost of waste removal. This will amount to £450 on average.

Cost breakdown for a small drain could amount to around £1,000. You’re looking at £750 for tradesmen hire and £250 for materials.

Frequently asked questions

Below are some of the frequently asked questions raised by customers looking to build an extension.

Can I build over a drain?

Building over your drain can cause complications. While it isn’t out of the question, you should still contact your local water authority and sewerage company to find out about the viability of such a plan. If the risk to the drainage system, including all of the pipework, is minimal, then you might be granted permission. So long as regulations are being met, work might still be able to go ahead.

In some cases, you don’t need to seek approval from your local water authority. If the sewer is private and only linked to your property, then you should be able to go ahead with your plans. However, it is still in your best interest to double-check, as if you do build over a drain without permission, and it is later discovered that your drainage system does extend elsewhere, your extension might have to be demolished after building work has finished.

If I can’t build an extension, what are my options?

If you aren’t granted permission to extend your property over a drain, or if the drain can’t be moved, then you are going to have to rethink your plans. If you’re intent on building outwards, you will have to choose a locale that is unaffected by the drainage system. By retrieving any plans of your home from the local council, you might be able to source a new location. And as we suggested earlier, it is worth hiring a surveyor too, in the event that the drainage system highlighted on the plans has changed.

If you can’t build the extension you want, there are other ways to extend your home. You could convert your garage into an extra living space or add an extra floor to your property, so there are options available to you. We recommend getting in touch with ourselves, as here at Extension Prices, we can discuss some of the other options that could be suitable for your property. We will then send you a quote for the type of work that will need to be involved, and put you in touch with the trusted extension contractors that work with us.

If sewer pipes are damaged, will I be covered by my home insurance?

Most home insurance policies don’t cover damage to the sewer pipes, but it is worth checking with your provider. Of course, damage can be alleviated by delegating the work that needs to be carried out to the professionals, as they are less likely than you are to cause damage, as they will have the skills and experience necessary for the planned drain removal.

What are the dangers of building over underground drainage?

If you build over an existing sewer or drain, you could damage the pipes, and this could cause blockages and leaks. The main issue is that there will be access issues should there be a problem with the drain. When damage occurs, there could be a problem with nasty smells, environmental damage, and the risk of health-related issues. This is why you should consider moving a drain before building your extension, as any problems will then be alleviated. You will also save yourself a lot of money, as you won’t be responsible for any repair costs that might otherwise need to be considered should damage take place.

Contact Us

For more advice on all things extension-related, get in touch with our friendly team. Leave us a message on our site, and we will get back to you with the information you require. Take a look around our site too for information on the types of projects you might want to consider and the costs associated with each.

Rich Crossley
Having spent 30 years working all over the world for top-tier investment banks, I’ve owned and developed houses all over the world – Europe, the US and Asia. I’m now based back in the UK and involved in the property industry – oh, and I’m a keen DIY enthusiast!
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