Building An Extension Where To Start

Building An Extension Where To Start

Building an Extension Where to Start


There are many reasons to build an extension to your home.

The number one being that it will improve your quality of life and increase your living space, without having to move.

But another prime reason for doing so is that it will add immeasurably to your property’s value.

One of the first questions when building a home extension is where to start?

In this article, we set out the cost, profit and timescale of an extension to your home.



Based on an extension measuring five metres by four and costing between £1200 and £1500 per metre squared, we have worked out a typical estimate.

Therefore, the best-case scenario is a cost of £24000, for a five by four extension.

Don’t forget to add on between ten and fifteen percent, for services such as the architect, the structural engineer, the planning application and so forth.

And, we’re not done yet with the extras. There is also then VAT to factor in.

So, therefore, we are looking at a figure of around £32000. A bargain if you consider the extra space and value.

That’s assuming you don’t have the misfortune to live in London, where everything will shoot up in price even more.


So, what would that be for two storeys being extended?

We suggest you add on half again, for the basic cost of the build, then add the ten to fifteen percent in fees and the VAT to that.

In other words, the lowest estimate would be in the region of £48000. A double storey extension is usually cheaper per square meter as the majority of the work has already been done in the footing, planning etc. The top floor is usually an extra bedroom or two that doesn’t require any much work after the brickwork and plastering.


Otherwise, there are a whole load of other factors that could push up the cost of your build.

Are you adding a bathroom or kitchen?

The general price to add for a bathroom is £5k  or £10k (kitchen) It is your own preference on what to spend in a bathroom and kitchen, but some great bargains can be found if you shop around. these are usually one of the biggest costs that add to your extension.

Also, things like glazing, tiling, fitted joinery and more intricate designs will put the prices up. As will factors such as limited access to the site, structural changes and the moving of any fixtures or fittings.

The above quote is an estimate for a basic level of fittings and fixtures.

If you want more, it will cost extra. A five-star deluxe finish could put the costs up considerably but the level of quality is down to the client ultimately..


Oh yes, is the short answer to this question!

According to property experts Zoopla, home improvements in general add on an average of £30000 to a home.

An actual extension garners an additional £14000 to your home and comes high in the list of home improvements, which will yield a lucrative result.

A survey by Nationwide, found that a double bedroom with an en suite could add an extra 23% on to the value of a home.

This is better than the value that either a lone double bedroom (12%) or a single bathroom (6%) bring, even added together.

And for the best type of extension, in terms of return on investment? A conservatory. This wins hands down every single time.

The average profit for a conservatory is £5750. This is for an estimated cost of £5300 initially.

Other great home improvement suggestions include a loft conversion.

This could yield a profit of approximately £12k, for an investment of £24.6k.

Loft conversions have the advantage of not needing to be actual physical extensions, by virtue of the fact that the loft is already there and just a space that is waiting to be used.

Also, it is possible you may not need to seek planning permission for some types of loft conversion.

Whether you do need planning permission or not, depends on how much you are having done and if you are going to actually extend the space drastically or simply convert what you already have.

Even if you do extend the loft, if it is within the permitted guidelines, you will not have to seek planning permission.

More statistics reveal that the average extension costs close to £20k and creates a 71% average return on investment.

Whether you convert your loft, extend it, add a conservatory or do something else, your home improvement is set to earn you a profit.

Building an Extension Where to Start



Each job is different so we can’t really give a definite time scale.

A standard extension without bi-fold doors with the minimum of knock throughs will take 10 – 12 weeks as soon as we get go ahead and start digging the foundations.


The first week is preparation. This means warning your neighbours of the upcoming inconvenience.

Preparation includes ordering a skip and finding somewhere to store all the materials.


This week your drains and trenches will be dug. Also, the concrete base will be laid.

Building Control should approve and oversee the foundation work.


Now things are really taking shape. The bricks are starting to go down forming the outer and inner skins.


The bricks are still being laid. the first floor joists have been fitted and the floor boards laid and covered to continue building.


The roof joist should be going on. Any knocking through should be done and then the doors and windows are placed into their frames, giving the whole extension a more finished look.

The first fix of the joinery, plumbing and electrics is begun. Rendering to external walls is also finished.


Plastering and finish to external works.


The electrics and plumbing are completed, with taps, sockets and light fittings going in.

The décor and painting are undertaken at long last and the flooring or carpeting is laid.


This is the final stage of the work, where any outstanding jobs are completed any landscaping and general tidying.

So, the final answer is it should take around three to four months for a simple extension to be completed – if everything goes according to plan.

As stated every job is different and this guide is just an outline of what to expect but we are confident that things often go very smoothly and we can keep relatively close to this time scale.

Read more about the building process here in part two of our home extension guide Preparation.

Please get in touch for a free quote.