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What is the cost of moving drains for your home extension?

Updated: May 1

Drains in your garden can be a problem if they are in the way of your new home extension, however, the good news is that drains can be moved.

  • The cost of moving a drain to make way for your home extension.

  • Is permission required from the local water authority needed?

  • Can I move a drain myself?

  • Can I build a home extension over a drain in my garden?

If you’re planning to add an extension to your home and there is a drain in the way this will need to be either built over or relocated to ensure the drains do not get in the way of the foundations of your planned home extension.

Drains are part of complex networks of pipework, sewers and manhole covers, so it isn’t always a matter of moving just one drain. You may need to rebuild a drainage system in a new location, making sure it’s at the right depth (and this can be deep underground). You may also need to get permission from your local water authority, which can add to the cost.

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Average UK Cost

Moving a drain (materials)




Moving a drain (labour)




Drainage relocation design




Permission from the water authority




The average cost to move a drain will be around £4,500 to move a drain for a home extension, including the cost of labour and materials. More complex drain systems can cost up to £6,000.

If you are wanting to move a manhole or inspection chamber a good guide would be to allow around £1,000 to move the manhole, plus additional costs for cleaning up and refinishing the area. Moving a manhole is a messy job and can often make your garden very messy which may need re-landscaping or re-turfing.

Using a mini digger will make it a lot easier for your builder and in turn more cost-effective.

Consider if your access is suitable to get a micro-digger or mini-digger to the area that will be excavated.

You also need to allow the £750 cost of getting permission from your local water authority to move the drain.

Is permission required from the local water authority needed?

If your home extension is to be built within 3m of a public sewer or lateral drain, UK Building Regulations state that you must obtain approval from your local water authority.

If your home extension is outside the 3m it’s still worth checking with the relevant weather authorities before starting work – just in case.

Can I move a drain myself?

It's not recommended to take on drainage work as a DIY job as drainage systems can be quite complicated. Here at Excela Architecture we always recommend using a qualified drainage expert to undertake the work.

Can I build a home extension over a drain in my garden?

The short answer is Yes, but this will require a build-over agreement from your local water authority.

At Excela Architecture our architects will always look to design the structure of your home extension to incorporate bridging lintels to bridge over existing drains where the drains cross the foundations of the home extension rather than costly works such as moving and relocating existing underground drainage.

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