BuildGuideClear help for your home projectSign in
Premium Project Pack

House Extension Project Pack

Plan, price and run a single or double-storey extension without losing control of the budget or the programme.

  • 62-page PDF
  • 15 templates
  • Instant download
  • Updated August 2026
See what’s included

Secure checkout coming soon — payments are not yet enabled.

What's included

Everything in this pack

The practical toolkit for anyone extending their home — from feasibility and budget through to snagging and sign-off.

PDF

The 62-page extension handbook

Every stage of an extension explained, with realistic timescales and the decisions that matter most.

Spreadsheet

Budget and contingency planner

A structured cost model covering design, approvals, build, finishes and the 10–15% you should hold back.

Editable

Quote comparison template

Compare builders like for like so you can see what is included, excluded and hidden.

Printable

Build-stage inspection checklist

What to look for at foundations, damp-proof course, structure, roof, first fix and completion.

3 templates

Party wall and neighbour pack

Notice templates, timelines and a plain-English explanation of when the Party Wall Act applies.

Printable

Snagging list template

A room-by-room snagging sheet to complete before you release the final payment.

Who is this for?

Built for you if…

Homeowners planning an extension

You know roughly what you want and need a realistic view of cost, time and approvals.

Budget-conscious builders

You want to avoid the overruns that turn a £60k job into a £90k one.

People managing their own trades

You are acting as your own project manager and need stage-by-stage structure.

Table of contents

What you'll work through

Part 1 — Feasibility and design

  1. What your plot and property will realistically allow
  2. Single vs double storey vs wrap-around
  3. Setting a budget that survives contact with reality
  4. Choosing a designer and structural engineer

Part 2 — Approvals

  1. Permitted development limits for extensions
  2. Planning applications for extensions
  3. Building regulations and inspection stages
  4. Party wall notices and awards

Part 3 — Building it

  1. Finding and vetting builders
  2. Contracts, payment schedules and retentions
  3. Managing variations without losing control
  4. Completion, certificates and snagging

Inside the pack

Example pages

A look at the layout and depth you can expect. Final pages may differ slightly.

  • Extension type comparison
  • Budget and contingency planner
  • Quote comparison template
  • Building regs inspection stages
  • Party wall notice timeline
  • Snagging list

Reviews

What homeowners say

Homeowner reviews will appear here once the pack is released.

Homeowner reviews will appear here once the pack is released.

Homeowner reviews will appear here once the pack is released.

Pricing

One pack, one payment

House Extension Project Pack

£39£59

One-off payment. Lifetime access to updates.

  • 62-page extension handbook (PDF)
  • 15 editable templates, planners and checklists
  • Free updates when the rules change
  • Instant download, no subscription

Payments are not enabled yet — this is a preview of the pack.

Prefer to start free?

Every BuildGuide guide and tool stays free. The pack simply gathers the templates, trackers and detail into one place so you are not piecing it together yourself.

Browse free guidesAsk Mason

Instant download once payments go live.

FAQs

Frequently asked questions

Does the pack include cost data?

It includes cost structures, ranges and a planner you fill in with local quotes. Prices vary widely by region, so we teach you how to build a reliable number rather than quoting a national average.

Is it useful if I have already appointed a builder?

Yes. The inspection checklists, variation tracker and snagging list are most valuable once work is under way.

Does it cover loft and garage conversions?

The approvals guidance applies broadly, but the pack is written around extensions. Dedicated packs for conversions are on the way.

Ask Mason

Not sure this is the right pack?

Describe your project and Mason will point you to the guidance — free — that fits your home and situation, including whether the House Extension Project Pack is worth it for you.

Start with Mason

Recommended next steps

Read next

Extensions 10 min

Planning Your House Extension

From first sketch to shovel-ready drawings, learn the practical steps that lead to a smooth, well-priced extension project.

Read guide
Building regulations 9 min

Structural Work and Party Wall Basics

A plain-English guide to structural work in the home and the Party Wall etc. Act 1996 for UK homeowners, covering when engineers are needed, what notices to serve and how to keep neighbours onside.

Read guide
Planning permission 11 min

Do I Need Planning Permission?

Find out whether your extension, loft conversion, outbuilding or home improvement needs planning permission. A clear UK guide for homeowners.

Read guide
Planning permission 10 min

Permitted Development Rights Explained

Understand what Permitted Development Rights cover, the limits that apply and how to check whether your extension, loft conversion or outbuilding qualifies.

Read guide

Recommended tools

Interactive tool

Extension Feasibility Checker

Answer seven quick questions and see how likely planning permission, permitted development, building regulations and the Party Wall Act are for your extension.

Open tool Interactive tool

Ask Mason: project checker

Describe your project and get tailored, plain-English guidance on the approvals, steps and risks that apply to your home.

Open tool Interactive tool

Building Regulations Checker

Answer a few short questions about your home improvement for an early, plain-English indication of whether Building Regulations approval is likely to be required.

Open tool

You may also need

Recently updated

BuildGuide Project Packs provide general guidance for homeowners in England. They are not legal advice, a planning decision or a professional design.