Home extension tips

Planning an extension to your house
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Extend or move?

When your home is no longer large enough for your household’s needs, building an extension is often the best option, so long as you like the location of your current property. This is particularly true if you live in an area where house prices are high, or you’re at the high end of the property market anywhere, because the Stamp Duty and other costs involved in moving such as your estate agent’s fees which are calculated as a percentage of the purchase price.

Extending rather than moving also avoids the hassle of the whole moving process!

Planning an extension: where to start

If you decide that extending is the right option for you, this home extension guide will help you plan an extension to your house that will serve your needs and be a pleasure to live in for years to come.

What to consider when planning an extension

One storey or two?

A lot of Britain’s housing stock comprises terraced and semi-detached properties with fairly small. galley-style kitchens. This layout reflects how people lived even up to the 1960s, when kitchen gadgets were limited and families sat down in a separate dining room to eat. Today’s families, however, want much larger kitchens where they can eat, which accommodate a dishwasher and probably a washing machine, and with worktop space for things like bread makers, smoothie makers and coffee machines. This is why single-storey, rear kitchen extensions are amongst the most common house extension projects.

However, while you’re going through all the disruption of having the builders in, the additional cost of adding a second storey to your home extension plans may be relatively small, and could gain you a guest bedroom or dedicated home office at the back of your house. That said, if you really have no need for this, there’s no point in spending more than is necessary when planning an extension.

Extending up, back and sideways

Extending upwards by doing a loft conversion is a popular way of adding bedroom and home office space. But for kitchen and living space extensions, it’s worth considering whether extending your house sideways would be a practical alternative or addition to extending the rear of your property to give you the space you need. However, if you do consider using the side return next to your property, check your local council’s planning regulations regarding how close your side wall can be to the boundary. It’s also worth finding out whether there are different rules for one- and two-storey extensions – two-storey extensions usually need to be further from the edge of your land.

Another extension option is to build an over-garage house extension by adding second storey over an integral garage. One of the main advantages of this option is that it doesn’t change the footprint of your house by eating into your garden, but many councils do not permit this type of development when your garage is adjacent (less than two metres away) to your neighbour’s in streets of semi-detached properties because it leads the general look of the road becoming terrace-like. Homeowners who are able to do this often find that they actually need to knock down the original garage and start again because the additional second storey requires better foundations than the original garage did.

It’s rare to be able to extend your house forward of the street’s ‘building line’.

Think ahead

Although often less expensive than moving, a house extension is a considerable investment so it’s worth making sure that your home extension plans will serve your family’s needs in the long term as well as now. For example, when planning an extension over your garage to give you an extra bedroom to accommodate another child, it may be tempting to use some of the space for an en suite for the master bedroom. However, if this means that the size of the extra bedroom is too small to accommodate a desk where your new baby can do his or her homework in future years, it may be better to give the extra shower room a miss.

How to make the most of professionals when planning home extension

If your existing home or planned extension are particularly luxurious, it may well be worth engaging an architect who can bring flair and ingenuity to your home extension plans. For more standard requirements, an architectural designer can usually come up with an appropriate design and draw up the plans that your builders need at a considerably lower cost.

Tip: Whether using an architect or architectural designer, tell them the outcomes up you want (e.g. a large, light kitchen we can eat in) rather than the means to achieving those ends (e.g. a rear extension with a Velux window in a pitched roof) which could constrain their creativity.

Planning for extension: Frequently asked questions

When is planning permission required?

Government regulations allow ‘permitted developments’ without planning permission. Start by using the Planning Portal to find details of the latest specific limits that would be relevant to your situation when planning for extension. Then check whether your local planning authority has specific rules for your area.

Key points include:

  • Single-storey rear extensions must not go further than three metres from the original rear wall of a semi-detached or terraced house, or four metres for a detached house.
  • Two-storey extensions must not go further than three metres from the rear wall of any type of property.
  • A maximum of half of the area of land originally surrounding the property may be built on.
  • Single storey rear extensions can be up to four metres high.

Although applying for planning permission can feel like a hurdle to avoid at all costs, it’s usually free and if you’ve planned your project well, doesn’t add much time to its overall duration. It’s rarely worth reducing the scope of your home extension project substantially simply to avoid the need to apply for planning permission.

How much does it cost to build an extension?

Planning an extension costs as much as you are prepared to spend in most cases as the finish and materials you choose will dictate your budget. A minimum of £100 per square foot of floor space is a useful rule of thumb.

Where can I find an architect or architectural designer to draw up home extension plans?

There are architects and architectural designers who work with all types of property and you’re most likely to get a suitable solution for your home if you work with one who has lots of experience planning for extensions to your type of property at your budget. To find one, ask neighbours and friends in the area for recommendations – face to face or on a community website or Facebook page – or look up decent planning applications as these will contain the details of the professional who drew up the plans.

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