TOP 10 THINGS TO BE AWARE OF WHEN BUILDING A HOUSE EXTENSION

6 months into our Renovation and the ground floor and 1st floor extensions are complete.

Building a house extension is an exciting experience. I recently wrote a post on ‘A Guide to building work and all the extra costs that go into it’ which you can read here, but I thought i’d recap some of the key points which I feel are the most important to consider from the offset.

Here’s a checklist of things to be aware of when building a house extension.

How much can you extend a house without planning permission?

Under permitted development rights, you can extend your house to a certain extent without

planning permission, but this varies based on the type of extension. For a single storey

house extension, it can be no more than 4m in height when it is within 2m of a boundary,

with eaves no higher than 3m, and there are further guidelines for the width of the extension

depending on whether it is detached or semi-detached.

As there are so many specific requirements that need to be met depending on the type of

extension, it is best to err on the side of caution and consult an expert before beginning the

construction.

Do I need to comply with building regulations?

Before going ahead with building a house extension, you need to contact your local authority

to be sure that your planned extension complies with building regulations. These set out key

requirements to ensure that a building is safe, including in terms of fire safety and damp

proofing. Learn about how to damp proof walls using paint to maximise your chances of

approval.

Who do I need to hire to build my house extension?

You may choose to do the construction yourself, or in other cases, you might choose an

architect to design the plans for you. You can select contractors to build the extension, or you may let the architect choose their

own contractors. If you want an extra level of control over your construction, you can project

manage the construction yourself, or hire a project manager to oversee the work.

Do some research online, talk to friends about local contractors, and if you wish to take on

the project yourself, consider carefully whether you have enough time to dedicate to the

work.

How will construction work affect my home?

You should also consider the impact contractors will have on your home. As well as the

disruption to your home life that will come with builders entering your home, you will need to

ensure there is enough room for contractors to park their vehicles and store materials.

Will you feel comfortable staying in your home during the construction? You may need to

factor in costs for accommodation or have discussions with family members about possibly

staying with them whilst the work is being done to your property.

Do I need to take out site insurance?

It is vital to ensure that your home insurers are aware of any intended extensions to your

property. Many home insurance policies will not cover extensions, and your existing policy

may be undermined by any structures you build. You should never assume that builders will have insurance. In some cases, even if they do

have insurance, you may be required to prove you are not at fault when taking out a legal

claim against them.

Will my house extension cause conflict with my neighbours?

The Party Wall Act 1996 prevents and resolves disputes over party walls between

neighbouring buildings. If you intend to build a house extension on or close to a boundary

that you share with a neighbour, you will need to give your neighbours notice of your

intentions. If your neighbours disagree with the extension, the act provides a mechanism for

resolving disputes.

Factor in purchases for blinds, curtains and partitions if you feel concerned about lack of

privacy between the properties.

How should I plan for the costs of building a house extension?

You should factor your costs for the extension well in advance, including contingency plans,

as it is common for housing renovations to reveal wider issues with housing structure, etc. Before writing a list of planned costs for materials and construction, ensure you have

factored in all aspects of the work. You may need to reserve extra money for insurance,

plumbing, VAT charges, accommodation, amongst other things.

It’s vital not to cut back on quality, as selecting the highest quality materials secures the safety of your extension. For example, C24 Timber is the best choice for floor joists due to their high strength

How should I factor in the position of white goods?

If you intend for your extension to be a kitchen or bathroom, you will need to consider where

your plumbing or white goods will go, and if you need to have anything installed. Discuss the locations of any white goods, sinks or toilets with your designer and any building

contractors to ensure they are aware of changes that will be required. This factoring of white goods is a thing to consider if it’s a kitchen you’re extending, helping you to prepare for the cost of new appliances, including a fridge/ freezer that fits the new dimensions of your kitchen. 

Will I have to pay VAT when building a house extension?

Labour and materials for building a house extension will generally be subject to VAT at a

rate of 20%. You may be able to avoid the extra VAT charges on labour by using a local

builder who is not VAT registered, but you will still be required to pay VAT for any materials

Used. You may also be able to claim relief from VAT charges if your property is a listed or

unoccupied home, but you will be required to use a VAT registered builder.

How much glazing can I add to my house extension?

Building regulations dictate that the amount of glazing in an extension should be limited to

25% of the extension’s floor area. If your intended extension exceeds this amount, you can

deduct the total amount of windows and doors that have been removed due to the extension,

which should help you to fit within the guidelines.

If the amount of glazing still exceeds 25% at this stage, you will need to show that the

extension’s CO2 rate would be no higher than a compliant structure of the same size.

Now you’ve gone through the building a house extension checklist, it’s time to put your plans

into action. Take these aspects into account, and you’ll have a fantastic new extension that is fully compliant and fits your everyday needs.