---
title: "SoakawayCalculator.co.uk — Statutory & Financial Comparison Matrices (https://soakawaycalculator.co.uk/compare)"
source_url: "https://soakawaycalculator.co.uk/compare"
canonical_url: "https://soakawaycalculator.co.uk/compare"
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# SoakawayCalculator.co.uk — Side-by-Side Statutory Comparison Hub

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

## [BRE Digest 365 Soakaway Sizing: Geocellular Attenuation Crates (95% Void) vs Rubble Pit (30% Void)](https://soakawaycalculator.co.uk/compare/crate-soakaway-vs-rubble-soakaway-bre-365)
- **Direct Answer:** Under BRE Digest 365 ("Soakaway Design") and Approved Document H3, a geocellular polymer crate soakaway provides a 95% void ratio compared to 30% for granular hardcore/rubble—reducing the required excavation pit volume and spoil removal cost by 68% for the exact same M5-60 / 100-year + 40% climate change storm storage volume.
- **Statutory Basis:** BRE Digest 365 (2016) · Building Regulations Approved Document H3 · CIRIA C753 SuDS Manual
- **Interactive Matrix & Calculator:** [https://soakawaycalculator.co.uk/compare/crate-soakaway-vs-rubble-soakaway-bre-365](https://soakawaycalculator.co.uk/compare/crate-soakaway-vs-rubble-soakaway-bre-365)

## [BRE Digest 365 Soil Percolation Test (f-Value) vs Building Regulations Part H3 Surface Water Drainage Hierarchy (2026 UK Guide)](https://soakawaycalculator.co.uk/compare/bre-digest-365-percolation-test-vs-building-regs-part-h3-surface-water-hierarchy)
- **Direct Answer:** Under UK Building Regulations Approved Document H3 (Paragraph 3.2), surface water from new extensions and roofs must follow a strict 4-tier statutory drainage hierarchy: (1) infiltration soakaway into the ground, (2) discharge to a surface water body/watercourse, (3) discharge to a public surface water sewer, and (4) discharge to a combined sewer—and Building Control will not permit skipping Tier 1 (soakaway) on clay ground unless you submit a formal BRE Digest 365 3-cycle trial pit percolation test proving soil infiltration rate (f) is slower than 1×10⁻⁶ m/s or the 24-hour half-empty time (t₅₀) fails.
- **Statutory Basis:** BRE Digest 365 (Soakaway Design 2016) · Building Regulations Approved Document H3 Paragraph 3.2 · CIRIA C753 SuDS Manual
- **Interactive Matrix & Calculator:** [https://soakawaycalculator.co.uk/compare/bre-digest-365-percolation-test-vs-building-regs-part-h3-surface-water-hierarchy](https://soakawaycalculator.co.uk/compare/bre-digest-365-percolation-test-vs-building-regs-part-h3-surface-water-hierarchy)