How Much Does a Double Storey Extension Cost?

Thinking of carrying out some much-needed renovations to your home? Trying to make your tired old place feel new again? An extension can help you fall in love with your home again and add valuable, functional space where you need it most, giving the rest of your home a little extra room to breathe. And if you’re thinking of adding an extension, doubling up can be highly beneficial in a number of ways. In the age of “don’t move, improve” extensive renovations like house extensions can lend your property a new lease of life while potentially insulating you from the caprices of the property market.

But how much can you expect to pay for a double storey extension? What logistical or legal difficulties can you expect to encounter? And will the benefits outweigh the caveats? We’ll try to answer all of these questions and more on this page.

How much does a Double Storey Extension Cost?

We don’t want to bury the lede here so we’ll just cut straight to the quick. While your mileage may vary depending on the type of materials you use and the size and nature of your property, by rule of thumb, a two storey extension will cost roughly 50% more than a single storey extension.

Let’s take a fairly average sized 18 square metre (3x6m) room size and use it as the basis for our proposed extension. With this figure we can extrapolate roughly what our two storey extension would cost.

We allow between £2,500 and £3,000 per square metre, depending on finishes.

An extension will set you back around £45,000-£55,000. This assumes that window sizes are standard, bathroom suites are pretty middle of the road and that there’s no need for any purpose joinery or glazing. Given how much extra this can add to the value of your property this figure makes for a pretty impressive return on your investment (more on that later).

If, however, you have your sights set on something a little grander with custom timber cladding, more extensive glazing or a grander kitchen or bathroom design you can expect to pay anywhere between £70,000 and £80,000.

Please note that these figures are intended as a guideline and you should always speak to an architect before proceeding with these kinds of major renovations.

Does a Double Storey Extension require planning permission?

In most cases, two storey extensions do not require planning permission as long as they meet the following requirements;

a) The heights of the pitch and eaves and pitch heights must not exceed the height of the existing house. If the property is within two metres of a boundary, the overall maximum eaves height is restricted to 3m. Roof pitch should be designed to match the existing house where possible.

b) The extension’s footprint should not exceed three metres from the original house and must be more than seven metres from the rear boundary (opposite the rear wall).Your extension must not exceed 50% of the total land areas surrounding your property.

c) The materials used should be as similar in appearance as possible as those used to make your existing house.

d) The extension must be behind the house proper. Two storey extensions to the side or front of the original house are not permitted.

e) The extension may not have any balconies or verandas. If you have your heart set on one of these, you will require planning permission.

f) Any upper floor windows in a side elevation must use obscured glazing and be non-opening, unless the window is above 1.7m from floor level inside.

The above also assumes that;

Your property is a house

Permitted Development rights apply to houses but not flats, maisonettes or other types of buildings. While you may be able to extend a property of this type you will certainly require full planning permission. What’s more, if your property has undergone a change of use (such as being converted from a barn, mill or warehouse into a home, this may affect your permitted development rights. Always check with your local authority’s department of planning.

Your house is not listed, neither are any other buildings contained within your boundaries

Development of listed buildings requires specific planning consent which usually demands a lot more detail than a standard planning application.

Your home is not within a designated plot of land

Buildings within designated spaces such as National Parks, World Heritage Sites or areas of Outstanding Natural Beauty cannot be extended without full planning permission.

Is it worth it? The benefits of a double storey extension

A two storey extension can be a cost effective way of gaining maximum floorspace for your property, without eating too much into your garden. It will also mean that your house isn’t bottom heavy, which can be an issue with some large single storey extension projects where they have a huge living space but a lack of sleeping accommodation above.

What’s more, it can add significantly to the value of your property. As much as 11%. According to Zoopla, the average value of a house in London is £644,215. Let’s assume that your property is fetches this average price. With an added 11% that adds an increase of £70,863.65 boosting your home’s value to over £715,000. Assuming you spent around £45,000-£55,000 on an average extension that makes for a pretty healthy return on your investment of over £15,000-£25,000.

Even if you have no intention of giving up your highly desirable London property any time soon, that’s still an impressive increase that will give you peace of mind even in a tumultuous property market.

Get it right, let us in on the ground floor!

Even a modest double storey extension can be a costly process and there’s a great deal that can go wrong. Which is why it’s so crucial to get an experienced and knowledgeable architect involved from day one. Preferably someone with in-depth knowledge of your area and a good relationship with local authorities.

We can even liaise with local authorities on your behalf to check whether planning permissions are necessary. Want to know more? Get in touch with us today. We can’t wait to help you unleash your home’s true potential.

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