House Extension Cost
Planning an extension guide with costs and advice
Extending your home is becoming a very popular way to gain additional living space in the UK without having to move. When you look at the costs involved with moving, the removal firm, the conveyancing, the estate agents fees, stamp duty etc, it can often work out cheaper to build an extension (plus the total cost of the extension, or more, can usually be recouped in terms of added property value if you ever do decide to move). Extensions will vary in cost enormously depending on the size, soil type, whether single or two stories, the amount and type of glazing, and of course the builder! For most of us, a house extension is definitely not going to be a DIY job, so a local builder or building company will be required.
Example costs for building an extension
Things to consider when building an extension
You still have to put a lot of thought into even the smallest extension to be sure of improving the property value. Plus there are also practical issues to consider such as access and parking if you are creating extra rooms (one of the main reasons for planning refusal is lack of off-street parking). Other practical and important aspects to consider before you start getting plans drawn are the existing services (where are they located and are they up to the job), the site soil conditions, history of flooding in the area, any trees near to the proposed extension, plus any right of way issues.
Whether your new extension requires planning permission or not, it will need Building Regulations Approval. These regulations are laid down to ensure certain design and construction standards are achieved in all new building. These standards cover many different aspects but are particularly concerned with safety, energy efficiency, drainage and access. To comply with Building Regulations you can either submit a full plan and have the building inspector visit the site at regular intervals to inspects the work as it proceeds. Or you can simply submit a Building Notice to inform the council that you will be complying with the regulations and give the building control department 48 hours notice before starting any work. This notice method is more risky as you do not have the benefit of an approved plan to work to and the building control surveyor cannot warn you in advance of any pitfalls, he may only notice after you have contravened a regulatory requirement, which could prove expensive.
Before you start work on any extension you need to assess your heating requirements and check that the existing boiler system can cope with the extra rooms. If your boiler does not have sufficient capacity you can add a second heating system or upgrade the original system by replacing the boiler. It may be cheaper long term to use electric heating via radiators or an under-floor system, rather than paying for a new boiler.
Doing it Yourself
Many people design their own extensions, using structural engineers or architects for advice and help with the planning. Others use their own design and employ builders who can take on the project. But it is unusual for homeowners to build an extension on their own as a complete DIY project. There are numerous advantages to hiring a professional to at least do the design work, plus of course, certain aspects of the project will need to be completed by a tradesman authorised under the competent person’s scheme, such as the wiring.
But building a home extension needn’t be overly difficult for anyone that is physically fit and has some DIY experience, however, if tackling this yourself you will need dedication and perseverance as due to Sods Law there will be upsets, delays and problems no matter how well you planned the project. Conservatories are a relatively easy to extend as kits can be bought cheaply with detailed instructions, but you need to make sure you choose a conservatory that fits the look of the house to be sure it will add value when it comes to selling. But even with a conservatory kit, there is still an awful lot of work to do, with the foundations/groundwork’s being particularly hard physical labour. Connecting plumbing for heating and doing electrics will not be a DIY task in most cases, however. Building a home extension from scratch without a kit isn’t as difficult as many think. But there is a lot of experience required when it comes to choosing the right materials and knowing when and where to use them. If you are a competent DIY enthusiast, then most of the work will be straightforward enough, but having an expert available to offer advice could be invaluable. Therefore, even when self-building, it is highly recommended that you at least pay for the services of an experienced architect.
Remember that if self-building a home extension then you need to make sure the insurance will cover you during the project. you will likely have to update your household and contents insurance plus cover yourself for possible damage to other people or their property while the project is in progress. This will usually require a separate “all risks” type policy in addition to the existing home insurance, though some insurers may be able to simply upgrade the existing cover temporarily.
Building an extension checklist
- Before you do anything sit down and decide exactly on your budget
- For some extensions you may not need planning permission, but you should check all local planning regulations and requirements before making any plans
- Bigger projects are not simple DIY jobs and you will need the services of an expert
- An architect can be a worthwhile investment and can help you to explore your building options
Hiring a Tradesman Checklist
- Always get at least 2 quotes before hiring.
- Never pay the full amount upfront.
- Get the quote in writing.
- For any payment you make, always get a receipt.
- On more expensive jobs, ask for references.
- Check if the tradesman is a member of any trades associations.
- Make sure the tradesman has public liability insurance.
Will I Need Planning Permission for my Extension?
Do I need to move out while extending?
How long does it take for my plans to be approved for my extension?
Ground floor kitchen shower extension.
Submitted by Sam
Hi there, planning to build a new bedroom top of the garage.
Submitted by Wasim
Single story kitchen diner rear extension, the same width of the house. Currently, 1 small extension/sunroom that is not keyed into the house which needs knocking out which will be replaced by this extension and remove the wall from kitchen to sunroom. Wanting to be done asap and completed within a ...
Submitted by Daisy
We have had an L-shaped extension done onto our house. It has been roofed and glazed. The builder did not finish the walls up to roof height, and left the job as he was offered a contract in London, and said his mate would come around and finish the job. His mate came around and fitted barge-boards ...
Submitted by Rick
Conversion of a conservatory to a dining room with a bit more extension to sideways. Building plan in hand.