Building Over Agreement (Thames Water Sizes Costs and Fees)
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There are two types of build over agreement If you’re building over or near a domestic sewer with a diameter of 160mm or less, you can potentially apply for a self-certified build over agreement. We may grant this if you’re able to confirm that your plans pose little risk to the pipe. We group sewers into three sizes, which determine the type of application you can make and the amount of survey work required and Thames Water cost.
If the sewer you’re building over or near is up to and including 160mm in diameter, you may be eligible for a self-certified agreement or may require a full agreement.
You need to apply for a full build over agreement if the sewer you’re building over or near is from over 160mm to 375mm in diameter. We’ll carry out a pre-construction CCTV survey to check whether any repairs are needed. We also carry out a second survey when your building is complete, to make sure the sewer hasn’t been damaged.
You also need to apply for a full build over agreement for sewers over 375mm in diameter. In this case, we may needto enter the sewer to carry out our pre- and post-construction surveys rather than using a camera.
How much does the application cost?
A self-certified build over agreement is free but can only be applied for if you’re building over or near a domestic sewer up to 160mm in diameter, you’ll also need to meet all of our criteria.
The cost of a full build over application depends on the size of sewer and whether your property is domestic or commercial.
Class 1 Up to and including 160mm (6”) Domestic £343 or £299 when applying and paying online Up to and including 160mm (6”) Commercial or new build £687
Class 2 Over 160mm (6”) to 375mm (15”) inclusive
Any £687 Class 3 Over 375mm (15”) inclusive Any £1,300*
*There is also a legal fee involved in entering into an agreement for sewers over 375mm in diameter, which is usually around £550. If you apply online you can pay using a credit or debit card.
What does the fee cover? For Class 1 sewers, the fee covers:
Processing your application • Technical reviews of your plans
Discussing and agreeing any design change proposals
Liaising with your building control officer
Issuing your agreement
Registering the agreement to build over or near the public sewer on our records For Class 2 sewers, it funds all of the above, plus two surveys of the length of affected sewer (pre- and post-construction). For Class 3 sewers, the fee again covers all of the above but the two surveys are likely to take a lot more time and be much more expensive.