Extension Book Resources

This page features the full list of links and resources referenced in our book House Extension Details.

We update the content regularly to ensure you have access to the most current and relevant materials.

Please refer to the list below for the latest updates.

Contents

01. Historical Context
02. Existing Building and Surrounding Context
03. Permissions and Planning
04. Upgrading and Retrofit
05. Extension Detailing / Detailed Design
06. Sustainability and the Environment
07. Extension Design
08. Material, Choices and Limitations
09. Budget
10. Project Management
11. Health and Safety
12. Building Regulations

Historical Context

The Housing Stock of the United Kingdom Report – BRE Trust
Justine Piddington, Simon Nicol, Helen Garrett, Matthew Custard
https://files.bregroup.com/bretrust/The-Housing-Stock-of-the-United-Kingdom_Report_BRE-Trust.pdf

Retrofit Internal Wall Insulation – Guide to Best Practice
Department for Business, Energy and Industrial Strategy
https://www.gov.uk/government/publications/retrofit-internal-wall-insulation-best-practice

Domestic 1: Vernacular Houses – Historic England
https://historicengland.org.uk/images-books/publications/dlsg-vernacular-houses/

Village Buildings of Britain – Matthew Rice

Timber Framed Buildings Explained – Trevor Yorke

Houses of Britain – John Prizeman

PAS2035 – Retrofitting dwellings for improved energy efficiency- Specification and Guidance
https://retrofitacademy.org/wp-content/uploads/2023/10/PAS2035_2023.pdf

BS5250:2021 Management of moisture in buildings
https://knowledge.bsigroup.com/products/management-of-moisture-in-buildings-code-of-practice-1/standard

Retrofit Internal Wall Insulation – Guide to Best Practice
https://www.gov.uk/government/publications/retrofit-internal-wall-insulation-best-practice

Retrofit Room in Roof Insulation – Guide to Best Practice
https://www.gov.uk/government/publications/room-in-roof-insulation-riri-best-practice

Research into resistance to moisture in buildings
https://www.gov.uk/government/publications/resistance-to-moisture-in-buildings

Retrofit insulation for Suspended Timber Floors: Best Practice
https://www.gov.uk/government/publications/insulating-suspended-timber-floors-best-practice

Solid Floor Insulation: Guide to Best Practice
https://www.gov.uk/government/publications/solid-floor-insulation-sfi-best-practice

Retrofit Pattern Book
https://retrofit.support/

Retrofit Pattern Book by 5th Studio
https://nationalretrofithub.org.uk/wp-content/uploads/2025/01/NRH-Retrofit-Pattern-Book.pdf

Retrofit for the Future
https://www.gov.uk/government/publications/retrofit-for-the-future-a-guide-to-making-retrofit-work

Environmental Design Pocket Book – Sofie Pelsmakers

Old House Eco Handbook – Marianne Suhr and Roger

Hunt

Sustainable Traditional Buildings Alliance
https://stbauk.org/

BS5250:2021 Management of moisture in buildings – code of practice – BSI bookshop Retrofit Hub
https://nationalretrofithub.org.uk/resource/archetypes-library-best-practice-guide/

Guide to Domestic Retrofit – Sustainable Renovation
https://www.thepebbletrust.org/sustainable-renovation-guide/

Devon Retrofit Guide
https://www.energysavingdevon.org.uk/document/devon-retrofit-guide/

Bristolian Guide to Solid Wall Insulation
https://sdfoundation.org.uk/wp-content/uploads/2018/01/2015_bristolsolidwallinsulationguidance.pdf

Extension Detailing / Detailed Design

Government Radon Map
https://www.ukradon.org/radonmaps/

NHBC 6.4.8 Timber joist spans
https://nhbc-standards.co.uk/6-superstructure-excluding-roofs/6-4-timber-and-concrete-upper-floors/6-4-8-timber-joist-spans/

Sustainability and the Environment

Building Regulations Approved Documents
https://www.gov.uk/government/collections/approved-documents

SAP – Standard Assessment Procedure
https://www.gov.uk/guidance/standard-assessment-procedure

Passivhaus
https://passivehouse.com/

LETI
https://www.leti.uk/publications

BREAAM
https://breeam.com

RIBA Climate Challenge
https://www.architecture.com/about/policy/climate-action/2030-climate-challenge

PAS 2035
https://www.retrofitacademy.org/memberships/wp-content/uploads/2021/02/PAS-2035-and-PAS-2030-2020.pdf

RIBA Sustainable Outcomes Guide
https://www.architecture.com/knowledge-and-resources/resources-landing-page/sustainable-outcomes-guide

UK Net Zero Carbon Building Standard
https://www.nzcbuildings.co.uk/pilotversion

Extension Design

Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice
https://www.brebookshop.com/details.jsp?id=328056

Nationally Described Space Standard – Technical Requirements
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/354095/03__140731__HSR_Supporting_Doc2_Space.pdf

Material, Choices and Limitations

Self Build Website
https://www.Self-build.co.uk

Self Build Estimating
https://www.self-build.co.uk/build-it-estimating-service/

Price a Job
https://www.priceajob.co.uk/products/estimate

Material Pyramid
https://www.materialepyramiden.dk/#

Budget

VAT on Extension Projects
https://www.gov.uk/guidance/buildings-and-construction-vat-notice-708#:~:text=You%20can%20zero%20rate%20the,within%20the%20enlargement%20or%20extension

Resi
https://resi.co.uk/advice/house-extensions/house-extension-cost

Build Partner
https://buildpartner.com

Price A Job
https://www.priceajob.co.uk

Plus Rooms
https://plusrooms.co.uk/cost-calculator/

Project Management

RIBA Contracts
https://www.architecture.com/digital-practice-tools/riba-contracts

JCT Contracts
https://www.jctltd.co.uk/category/contract-families

NEC Contracts
https://www.neccontract.com/

Health and Safety

CDM
https://www.hse.gov.uk/construction/cdm/2015/index.htm

https://books.hse.gov.uk/Construction

Building Regulations

Building Safety Act
https://www.gov.uk/guidance/the-building-safety-act

Building Regulations
https://www.gov.uk/government/collections/approved-documents

Build Over Applications
https://www.ofwat.gov.uk/households/your-water-company/contact-companies/

RIBA Guidance on changes to Building Safety Act for Architects who specialise in domestic projects
https://www.architecture.com/knowledge-and-resources/knowledge-landing-page/building-safety-act-for-architects-and-domestic-projects

Additional Guidance from RIBA
https://www.architecture.com/knowledge-and-resources/knowledge-landing-page/building-safety-act-regulations-updates-2023

RIBA Principal Designers Guide
https://www.ribabooks.com/RIBA-Principal-Designers-Guide_9781915722201

CIAT Principal Designer
https://architecturaltechnology.com/resources/building-safety/new/principal-designer.html