Knowledge Centre
Blogs, FAQs, technical downloads and guided journeys — everything you need to understand insulated raft foundations.
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Self-Builders
First principles, costs, and getting started on your self-build project.
Start journey →Architects
Thermal data, CAD details, specifications, and RIBA stage guidance.
Start journey →Timber Frame Companies
Precision tolerances, thermal performance, and trade partnership.
Start journey →Builders & Developers
Programme savings, compliance, and cost comparisons at scale.
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What Foundation Should I Choose for My Self Build?
How ground conditions, energy targets and programme should shape your foundation choice.
What Rising Energy Bills Mean for the Business Case for Fabric-First Design
Why low energy demand, smaller heating equipment and durable running-cost claims matter more as energy prices rise.
Why Housing Associations Are Choosing Passivhaus Before They Are Forced To
Lower tenant bills, reliable performance and fewer retrofit liabilities are making the case now.
Insulation Below vs Above the Slab
How insulation position changes thermal mass, comfort, and performance.
Minimum Concrete Thickness for an Insulated Raft
Why 200mm is the baseline in most domestic projects and when 250mm is needed.
Insulated Raft Foundations Explained
A practical primer on how insulated raft foundations work and where they fit best.
What is an insulated raft foundation?
An insulated raft foundation is a reinforced concrete slab that sits on top of a layer of load-bearing insulation, with more insulation wrapped around its...
Why Use an Insulated Raft Instead of a Traditional Raft with Insulation Above?
Insulation below the slab does more work, with less effort. When insulation sits above a concrete raft, the concrete sits outside the building's thermal...
What Is the Minimum Concrete Thickness for an Insulated Raft Foundation?
200mm for most houses. 250mm for taller buildings. If a supplier is showing you anything less, ask them to explain why. Structural calculations alone might...
Technical Details (PDF Library)
Typical Section
All
Standard Edge Detailing
All
Edge & Base Combinations
All
Edge Details — Common Variations
All
Brick Plinth Detail
Brick & Block
SD-0022 — Brick Support, DPM Under Slab
Brick & Block
SD-0022A — Brick Support, DPM Above Slab
Brick & Block
SD-0022B — Brick Support, Waterproof Concrete
Brick & Block
Solid Aircrete Wall with EWI
Brick & Block
Hollow Clay Blocks Detail
Brick & Block
Timber Frame & SIPs Wall Junction
Timber Frame, SIPs
Larsen Truss Detail
Timber Frame
I-Stud Twin Wall — Dual Bearing
I-Stud
Twin Wall I-Stud — Inner Bearing
I-Stud
Sole Plate Location Guidance
Timber Frame
ICF Wall Detail
ICF
Wood-Cement Fibre Blocks Detail
Brick & Block
Slate & Tile Edge Detail
All
Party Walls Detail
All
SD-0023 — Threshold Detail
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SD-0031 — EM10 Threshold Support
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SD-0032 — EM15 Threshold Support
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SD-0033 — EM20 Threshold Support
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ISOQUICK Threshold Support Brochure
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SD-0018 — Drains and Ducts
All
SD-0015 — External Tanking
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SD-0003 — General Sub-Base Arrangements
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Stepped Footing — Large
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Stepped Footing — Small
All
DPC & Full Radon Protection
All
Underfloor Heating Options Guide
All
Installation Guide — Part 1: Groundworks
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Installation Guide — Part 2: ISOQUICK Installation
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Installation Guide — Part 3: Brick Support System
Brick & Block
ISOQUICK Brick Support System — Introduction
Brick & Block
ISOQUICK Brick Support System — How It Works
Brick & Block
IQ Technical Specification
All
IQ-60e U-Value Tables
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IQ-90 U-Value Tables
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IQ-210 U-Value Tables
All
Kiwa BDA 3rd Party Certification
All