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The checklist
What to check in your extension quote
Each point lights up on the quote as you read.
- Whether planning permission is needed
Some house extensions can use permitted development rights, subject to limits and conditions. Confirm what applies to your property and plans before work starts.
- Building regulations approval, and who applies for it
Most extensions need building regulations approval. Agree who will arrange the application before work starts.
Source: Planning Portal: building regulations for an extension
- Any party wall notices needed for the work
Work on a party wall, building at a boundary or certain excavations near a neighbouring building can require notice. Check whether the proposed work is covered.
- The quote is in writing
Citizens Advice says not to rely on a verbal quote and to get it in writing.
- A fixed price, not an estimate
A quote gives an agreed price for specified work. An estimate gives an approximate cost. Ask which you’ve been given.
- When each payment is due
Citizens Advice suggests agreeing payment stages, with a chance to put problems right before the final payment.
- When the work will start and finish
If no time is agreed, the law only says the work must be done within a reasonable time.
- The insurance the business holds
Ask what insurance the business holds and to see the policies. Citizens Advice includes public liability insurance among the cover to check.
- Who takes away the waste
You must take reasonable steps to make sure waste from your home only goes to someone authorised to take it, such as a registered waste carrier.
- Cancellation information, if you agree the job at home
For a contract agreed in your home, the business must give you set information and a cancellation form, on paper or another lasting form.
Before you agree
Registrations and certificates to ask for
- Agree who will arrange building regulations approval
Confirm who will apply for approval and arrange the inspections before work starts.
- Check any party wall notice before setting a start date
The notice period depends on the work. Check which notice is needed and when it must be served before agreeing a start date.
The money
Know what you’ll pay and when
Citizens Advice says to keep the deposit as low as possible and not agree to more than 25%.
NI Direct advises avoiding large deposits and never paying the whole amount up front.
If you agree a job in your home, you can usually cancel within 14 days of agreeing it.
If you asked for work to start within those 14 days and then cancel, you pay for the part already done.
Ask the business
Questions to ask before you agree
- Does this extension need planning permission, or does it meet the permitted development rules? Planning Portal: extensions, planning permission
- Does any of this work need a party wall notice, and who will arrange it? GOV.UK: work you must tell your neighbour about
- Is this a fixed price or an estimate? Citizens Advice: before you get building work done
- What insurance do you have, and can I see the policy? Citizens Advice: before you get building work done
- Can I pay in stages, with the last payment once the work is finished? Citizens Advice: before you get building work done
- Who will take the waste away, and are they a registered waste carrier? GOV.UK: waste duty of care code of practice
- If we agree this at my home, will you give me the cancellation information in writing? Consumer Contracts Regulations 2013, regulation 10
Common questions
Questions people ask
Do I need planning permission for an extension?
Not always. Some house extensions fall within permitted development rights, but limits, conditions and property restrictions apply. Confirm what applies to your plans. Building regulations approval is a separate question.
When do I need to give a party wall notice?
The notice period depends on the work. Party-structure notices normally require at least two months; notices for new boundary walls or excavation normally require at least one month. Confirm the correct notice and timing before work starts.
How much deposit should I pay for an extension?
Citizens Advice says to keep the deposit as low as possible and not agree to more than 25%.
Should a quote be a fixed price?
A quote gives an agreed price for specified work. An estimate gives an approximate cost. Citizens Advice recommends getting the quote in writing.
Can I cancel building work I agreed to at home?
If you agree a job in your home, you can usually cancel within 14 days of agreeing it.
This guide covers England. Rules for building work differ in Wales, Scotland and Northern Ireland. It is general information, not legal advice, and it does not say whether a price is fair.