Free Extension Tools and Spreadsheets
Calculators, a budget spreadsheet, a building terms glossary, and the Approved Documents explorer. All free, all UK-specific, no account needed.
Most of the cost of getting an extension wrong is paid before anyone digs a trench. A budget with no contingency line, a quote nobody checked against typical rates, a decision made two weeks after the electrician needed it. The tools below exist to close those specific gaps, and none of them ask for an email address.
Extension Calculators
Free37 calculators covering costs, quantities and timings: foundation concrete, blockwork, insulation, roofing materials, screed drying, skip volumes, and professional fees.
Extension Budget Spreadsheet
Free downloadA ready-made budget spreadsheet with every cost category pre-populated. Fill in your quotes and it calculates your total with contingency automatically.
Kitchen Extension FAQs
Free21 answers to the most common questions about UK kitchen extensions: planning permission, costs, build stages, and finding builders.
Building Terms Glossary
FreePlain-English definitions for 1,300+ building terms: tools, materials, trades, concepts, and regulations. Search or browse A-Z.
Approved Documents Explorer
FreeEvery UK Building Regulations Approved Document, Parts A through T plus AD7 and the Manual, with a plain-English summary of each Part.
When you would use each one
These tools are useful at different points in a build. Reaching for them in the wrong order is why budgets slip.
Before you talk to anyone
Start with the extension cost calculator and the budget spreadsheet. A realistic total, with contingency, tells you whether the project is viable before you spend money on drawings. The permitted development limit checker and planning permission checker tell you which consent route you are on, which changes both the timeline and the professional fees.
While you are getting quotes
The builder quote checker and professional fees calculator give you the reference points to read a quote properly. The quantity calculators for foundation concrete, blockwork and roofing materials let you sanity-check the materials line rather than accepting a single lump sum. Our guide to comparing builder quotes explains how to make three quotes price the same job.
Once the build is running
The payment schedule calculator and certificates checklist keep money tied to completed work and stop certificates going missing. The glossary is there for the moment a tradesperson uses a term nobody explained, and the Approved Documents explorer for when you need to know what the regulations actually say.
What is free and what is not
Everything on this page is open. So is the structure of every build guide: you can browse the kitchen extension tree phase by phase and see exactly which tasks a build involves, in what order, without paying anything. The blog is open too, including the complete kitchen extension timeline, what a kitchen extension costs in 2026, and what happens at each building control inspection.
What sits behind the Access Pass is the step-by-step detail inside each task: the sequencing decisions, what to check before signing off a stage, the questions to ask each trade, and the mistakes that cost money on a real build. The free layer tells you what needs doing. The paid layer tells you how to do it without learning it the expensive way.