---
title: "BuildOverAgreement.co.uk — Statutory & Financial Comparison Matrices (https://buildoveragreement.co.uk/compare)"
source_url: "https://buildoveragreement.co.uk/compare"
canonical_url: "https://buildoveragreement.co.uk/compare"
retrieved_by: "AnswerRail Edge Engine v1.1.0-parity-v20 (https://answerrail.com)"
---

# BuildOverAgreement.co.uk — Side-by-Side Statutory Comparison Hub

> **Canonical Source:** [https://buildoveragreement.co.uk/compare](https://buildoveragreement.co.uk/compare)

## [Approved Document H4: Self-Certified Build Over Notice (150mm Pipe) vs Full Water Authority Agreement](https://buildoveragreement.co.uk/compare/self-certified-build-over-vs-full-water-authority-application)
- **Direct Answer:** Under Building Regulations Approved Document H4, building within 3 metres of or directly over a public sewer requires Water Authority approval: domestic extensions over 100mm–150mm pipes (<2m deep, no manhole covered) typically qualify for an instant free/low-cost Self-Certified Notice, whereas 225mm+ trunk sewers, depths >2m, or internal manhole relocations require a Full Build Over Agreement (£300–£1,350+) with pre- and post-CCTV surveys.
- **Statutory Basis:** Building Regulations 2010 Approved Document H4 · Water Industry Act 1991 s.104/s.185
- **Interactive Matrix & Calculator:** [https://buildoveragreement.co.uk/compare/self-certified-build-over-vs-full-water-authority-application](https://buildoveragreement.co.uk/compare/self-certified-build-over-vs-full-water-authority-application)

## [Thames Water vs Severn Trent, Anglian Water & United Utilities Build Over Agreement Fees & Rules (2026 UK Matrix)](https://buildoveragreement.co.uk/compare/thames-water-vs-severn-trent-anglian-water-build-over-agreement-fees-2026)
- **Direct Answer:** Under UK Building Regulations Approved Document H4, building an extension within 3 metres of or directly over a public sewer requires consent from the regional statutory Water Undertaker: while Severn Trent, Anglian Water, and United Utilities offer £0–£95 online Self-Certified Build Over Notices for domestic gravity sewers ≤150mm diameter meeting all standoff rules, Thames Water charges tiered 2026 statutory application fees of £349 (Class 1 ≤150mm), £686 (Class 2 150mm–375mm), and £1,394 (Class 3 >375mm or complex engineering).
- **Statutory Basis:** Building Regulations 2010 Approved Document H4 · Water Industry Act 1991 § 185 · Thames Water / Severn Trent / Anglian Water 2026 Charging Schemes
- **Interactive Matrix & Calculator:** [https://buildoveragreement.co.uk/compare/thames-water-vs-severn-trent-anglian-water-build-over-agreement-fees-2026](https://buildoveragreement.co.uk/compare/thames-water-vs-severn-trent-anglian-water-build-over-agreement-fees-2026)