What to Consider Before Starting Your House Extension

 

You like where you live but the space is tight and disorganised. Often a smart alteration of an existing layout could be the right answer. Carefully evaluate available space, how you use it and what can be done to improve it before you decide that extending up, sideways or at the back is the only solution to the problem. Building an extension is a disruptive process often taking a good chunk of a year, your finances and living arrangements. For this reason it is of utmost importance to decide what exactly your existing property is lacking that the extension could provide – it could be a new bedroom for your extending family, a bigger kitchen, home office or studio, larger living space, etc. This approach will result in a more appropriate and comprehensive solution than just blindly extending in pursuit of additional but unuseful and costly space.

 

The Cost of Building House Extension in London

 

The cost of an extension varies and mainly depends on:
– the quality of the build: standard, good and excellent (which on average costs 40% more)
– storeys & size (bigger is not always better)
– your involvement
– glazing amount
– kitchen (if extending it, its cost should be added to the list above)

If you are at the very beginning of your project, you probably aren’t in possession of detailed plans and specifications for your build, so it would be impossible to obtain a precise quote. At this stage you can only rely on ballpark estimates.
Extension costs in London and SE are higher than the rest of the country. A good estimate can be based on a cost per square metre, which ranges from £1850 to £2500+ and does NOT include VAT, professional fees or the cost of your new kitchen, bathroom, fitted joinery or glazing.
As an example, we can take an average cost of £2000 p/sqm for a basic build and an average size of 30 sqm single storey extension for a terraced house in London:
The cost would be £60000 + £12000 (20% VAT) = £72000. If using professionals, their fees will add 10-15% to the final cost. For a double storey extension you would have to add about 50% more.
Extension projects sometimes uncover hidden problems, and it is advisable to have a healthy contingency budget of 10-20% of your project value.

 

House Extension Legal Issues

 

Building Regulations for House Extensions

The Building Regulations equally apply to extensions as to any other build. They represent minimum legal requirements for your project – energy efficiency, structural integrity, ventilation, damp proofing, etc. The following are particularly important:

• Approved Document B – Fire Protection, Spread and Escape – dealing with the amount, position and size of windows as means of escape and provision of fresh air (along with garages as potential sources of fire)
• Approved Document LI – Insulation and Heating – your extension’s new roof, walls and floors must be constructed up to current standards regardless of how well, or not, your existing property is insulated. If you want a large amount of glazing (greater than 25% of new extension floor area) you would have to increase insulation levels of your new walls, possibly the existing ones and/or specify well insulated glass panels and windows. Calculation regarding the ratio of glazing are on a complex side, but worth pursuing.

Permitted Development

Some extensions (excluding listed buildings, flats/maisonettes and some new developments) will not require planning permissions as they would be considered Permitted Development under The Town and Country Planning (General Permitted Development). This will depend on the area you live in, the type of extension you want to build and is regulated by your local Planning Authority. Rear, side and two-storeys extensions, garage and loft conversion, with some strict regulations to follow, generally fall under Permitted Development. However, a wraparound extension might be judged differently and require planning application.

Planning Permission

You are legally required to obtain a Planning Permission if your extension project does not come under permitted development rights. In this case your local authority will need to assess your proposed design. You would have to submit existing drawings, your design proposal, and all information required by your planning authority.

Prior Approval

Required when you are building a larger rear extension or adding additional storeys. Prior Approval allows your local planning authority to assess whether your design meets the strict guidelines and how it impacts the surrounding area.

Lawful Development Certificate

Although not legally required, Lawful Development Certificate protects you in the event of policy changes and is a proof to your local authority and potential future buyers that your build was legal at the point of construction.

Insurance

Your existing insurance stops being valid with commencement of structural work on your property. Taking out a site insurance will make certain you are still protected. To protect yourself from dodgy builders going bust, as it sometimes happens, you can:
– take Developer Insolvency Insurance (or ask builders if they provide it)
– pay with credit card (valid up to £30000) as you would be protected by the Consumer Credit Act
– set up a staged payment plan (that’s how we do it at AD3London)
– hire a Project Manager (AD3London Project Manager is integral to our build projects)

Party Wall Agreement

Party wall is any boundary wall or structure where your and your neighbours’ lands meet. If your extension will be on or next to this party wall, you would have to consult your next-door neighbours to obtain Party Wall Agreement. Their consent might be straightforward, otherwise you could face a long legal process and fees.

Tree Preservation Orders
TPOs – Trees in your garden might be protected, and it is a criminal offence altering them in any way. They might invalidate your permitted development rights and in such a case planning permission might be necessary.

Other Considerations

• Sewers, drains and manholes locations on your property have to be carefully considered, as they can be tricky and costly to relocate
• Access, if restricted, can affect your project’s construction method
• Conservation Areas – your local conservation officer should be the first point of contact if you are planning an extension in such an area
• Overshadowing and Overlooking neighbouring properties – your neighbours’ rights to light and privacy

 

So What Are the Advantages

 

The list above is not exhausted but all the issues and potential problems are surmountable as proven by thousands of successfully completed extension build projects. The biggest advantage is that you would not have to go through one of the most stressful and costly events of your life – moving your home and starting your life anew in the pastures unknown. With patience, good planning and help from experienced professionals you would be able to:
– tailor your new extension to exactly fit your household needs
– create a new lifestyle without having to move
– improve the comfort and energy performance of your home
– increase the value of your property

For inspiration visit our Pinterest page dedicated to house extension projects.

Contact us to discuss your project via chat option or contact form.