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UK House Extension Episode 4 - Builder

Updated: Apr 15, 2022

Builder working on house extension

Selecting your builder will be the most important decision you will make in your extension journey. Every building project will have its ups and downs and partnering with the right builder will go a long way in ensuring your dream extension is completed without hassles. Once you have the designs from your architect then you can use that to get formal quotes from the builders. Best to take quotes from at least three builders for comparison. Most likely you will approach and select builders whose reference you have received from family, friends and colleagues.


Some aspects you need to consider are:

  • How big is the builder?

  • Does the builder have a fixed office and a fixed contact phone and preferably a website showcasing their projects?

  • How many projects the builder is executing simultaneously?

  • Is the builder using the same team to work on different projects or has multiple teams?

  • Has the builder executed local projects in your area?

  • Will the builder let you visit one of their sites and talk to their clients in private?

  • Does the builder have Insurance and Employees liability cover?


Once you get the quote from your builders you need to look for hidden extras or unclear work scope:

  • Is flooring/tiling covered in the quote or is it included on a per SQM basis?

  • Is installing bi-folding doors, windows, front porch door included?

  • Is Kitchen installation included?

  • What is covered under electrics and media? Is it a fixed price and not depending on number of sockets and fittings or has the builder quoted on a per point basis?

  • What is included in doing good, if for e.g. you are removing a chimney stack then will the builder paint the whole room or only the wall on which stack was removed?

  • Is the builder supplying, installing a new boiler or re-installing your old boiler?

  • Does the quote include all the works you had specified?

  • Has the builder specified what you will be expected to buy and what the builder will provide?

  • Does the builder know if you will be staying elsewhere during the build or will be living in the property and has he planned his schedule accordingly?

  • Will the builder make good any damages to neighbours’ property?

  • Will the builder do a deep cleaning at the end of the build?

  • Will the builder prime and finish woodwork like doors, skirtings, etc.?

  • Will the builder arrange for skips?

  • Will the builder unload heavy deliveries like tiles, flooring, etc.?

  • Will the builder help move your interior furniture?

  • What time will the builder work on Weekdays and on Saturday?

  • Is the builder providing grouting and adhesives for tiles?


A good builder will:

  • Give you a timeline for completion

  • Divide the contract value over the number of weeks work will be carried

  • Will not charge you a deposit

  • Weekly payments will be based on committed work for the week in the contract

  • Will provide an Insurance backed Guarantee of 10 years on structural and roof elements

  • Will have a 1-year defect liability period

  • Structural movements (Cracks) will be covered for 1 Year.

  • Will keep the site safe by boarding, railings and will arrange for a portable toilet for the crew

  • Will always be contactable and communicate promptly to your queries

  • Give you a list of things you would be expected to supply along with time when needed


You also need to be prepared for extra work that may arise during the extension for e.g.

  • Replacing your incoming mains water pipe with a 25mm Blue pipe. This is worth doing to increase water pressure. This may also be necessary if your existing water pipe is made of lead. Your water company may replace lead pipes for free.

  • However hard your builder tries your wall in other parts of the house will need painting

  • It may not be possible to have the skip in your front drive, in which case you will have to apply to council for keeping the skip on designated area on the road

  • Existing copper pipes connected between your boiler and radiators, taps may have oxidised and need replacing

  • Replacing existing radiators or adding TRVs

  • Installing a Smart Thermostat like Nest

  • Installing a Video Door Bell like Nest or Ring

  • Installing a Patio or steps from your extension to the garden

  • Staircase bannister and hand rails

  • Moving electric meter if doing an under-staircase WC

  • Relaying the lawn if damaged during construction phase

  • Builders will quote for a 1m foundation. An building inspector may ask for a deeper foundation if for eg due to a nearby tree

  • Installation of Water Softener and filter

  • You will need to provide Parking permits to the builder if necessary


Building Control

You may also discuss with the builder the plan for Building Control approval. You can use your local council provided inspection service or opt for an Independent Approved Inspector service. The independent service will be more expensive than the council offered service but could offer a much faster turnaround time for inspections. Builder cannot progress certain parts of the the build till inspected by the building inspector for eg the inspector will have to check the foundation depths before the foundations are filled. If you are on a tight completion schedule then you can opt for independent inspector. We used for our build.


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Gabriel Brown
Gabriel Brown
Apr 16, 2021

For container aded to the biding we need planing permission?

Gabriel Brown
Gabriel Brown
Apr 16, 2021
Replying to


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