Knowledge Centre
Blogs, FAQs, technical downloads and guided journeys — everything you need to understand insulated raft foundations.
Who is this for?
Choose your path and we'll walk you through the essentials for your role.
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.
Start journey →Browse all content
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
All
SD-0031 — EM10 Threshold Support
All
SD-0032 — EM15 Threshold Support
All
SD-0033 — EM20 Threshold Support
All
ISOQUICK Threshold Support Brochure
All
SD-0018 — Drains and Ducts
All
SD-0015 — External Tanking
All
SD-0003 — General Sub-Base Arrangements
All
Stepped Footing — Large
All
Stepped Footing — Small
All
DPC & Full Radon Protection
All
Underfloor Heating Options Guide
All
Installation Guide — Part 1: Groundworks
All
Installation Guide — Part 2: ISOQUICK Installation
All
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
All
IQ-90 U-Value Tables
All
IQ-210 U-Value Tables
All
Kiwa BDA 3rd Party Certification
All