Planning a home extension

Planning an Extension

Unsurprisingly, many people have found themselves feeling as though they have outgrown their home during the lockdown, and with the stamp duty holiday pushing up average house prices, the demand for home extensions and additions jumped by 52% in 2020.

Adding extra room in your current home can create some much-needed space without the hassle and financial burden of moving. This can be in the form of a loft or basement conversion, a garage extension, side extension, or a double or single storey rear extension.

Here are the five key questions to ask before embarking on a home extension project.

Will the extension add value?

On average, an extra bedroom or basement conversion can increase your home’s value by up to 15%, and an interior loft conversion may add up to 21%. So before you commit to a home extension, make sure that any added value will not only be enough to recoup the cost, but also that it doesn’t push the price of your property above the “ceiling” value for your area. This can be tricky to assess but researching similar local property sale prices via websites such as will help.

Will I need planning permission?

Planning rules have changed for England and Wales and you can find more information via Generally speaking, the more ambitious the extension the more likely you are to need planning permission. This may apply for example if your extension covers half the area of land surrounding your home, or extends towards a road, you’re increasing the overall height of the building, you’re using materials that differ from the original style of the house, your house is listed, etc.

Should I hire an architect?

An architect can be very helpful in managing the whole process. It’s best to pick a designer with a style or track record of projects that match up to what you’re trying to achieve. Plus if you use a local firm they will be more familiar with the local planning rules and how to work with planning committees.

Where do I find a builder?

As with most things these days, asking local friends or neighbours who have had work done on their homes is a good first step. Social media feeds are usually full of people asking for and giving recommendations. You can also try trade bodies such as the Federation of Master Builders. When looking for referrals ask to see examples of completed work and ask questions such as: Was the project completed to schedule and as expected? Was it finished on budget? Were there any unforeseen problems and how were they dealt with?

How should I budget?

Start with the high-level cost, which might be difficult because neither architects or builders like to commit until there are plans in place. has a handy Extension Cost Calculator that will help. Once you have a high-level cost you can draw up a detailed budget that needs to include VAT and professional fees as well as costs of materials, skip hire, etc. Then add a contingency of at least 10% for any unforeseen expenditure and keep updating it as you go along.


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