The Price of a House Extension in Essex for 2021

The Price of a House Extension in Essex

Wondering just how much a home extension will cost? Our guide is all you need to get a price estimate for your property extension before you seek out quotes.

Make sure you know what to expect going into your house extension quote to avoid any hidden surprises.

A single storey extension by Bush Builders


Single Storey Extensions

Double Storey Extensions

Kitchen or Bathroom Extensions

Additional Costs

Finishes and Fittings

Site Constraints


House extensions are an increasingly popular way to improve your home, and it’s not hard to see why. When it comes to choosing between moving or renovating, building an extension is often the more economically efficient option.

House extensions can:

• Add space and increase functionality
• Add value to your property
• Provide an alternative solution to the stress of buying and moving
• However, it’s important to get a proper understanding of the current rules, regulations and costs involved in a home extension before you get planning.

Of course, the overall cost will vary depending on a number of other factors, such as:

• Extension size
• Geographical location
• Soil type
• Standard of specification
• How much glazing you plan to use
• What the extension will be used for
• Accessibility and condition of the existing building

Generally speaking it’s likely that your budget will be split roughly 50/50 in terms of construction costs and interior costs, but there are many individual expenses to consider.

The following gives a breakdown of the average costs you’ll need to account for when building a house extension.

Basic Costs

A rear extension completed by Bush Builders in Romford

Single Storey House Extensions

Probably the most popular choice amongst families of all ages, this type of extension is a relatively straight-forward way to increase space and value.

Although it can vary depending on the quality, the average cost allowance in London/South East for a single storey extension is around £2,000 per sq/m.

On top of this, you will need to add 20% VAT as well as professional fees (such as structural design, architect involvement, building control, building regulation, and planning permission applications), which usually amount to around 10-15%.

Based on this, the estimated cost of a 5m x 5m single storey house extension will be:

Basic cost: 30sq/m = £33,000
+ VAT: £6,600
+ Fees: £2,000
= £41,600

Double Storey Home Extensions

An excellent example of a double storey extension

Despite what you might think, adding another storey to your house extension doesn’t mean doubling the costs – in fact, as you have already factored in the cost of your foundations and roof, it often works out to be not much more expensive than a single-storey extension. This is important to note when balancing your costs against the added value of your extension.

As a general rule, you can expect to add around 50% (if both storeys are the same size).

So the approximate cost of a 5m x 5m double-storey house extension will be:

Basic cost: £45,000
+ VAT: £9,000
+ Fees: £2,000
= £56,000

Additional Costs

A kitchen refurb as part of an extension in Brentwood

Kitchen or Bathroom Extensions

If you’re planning on using your new space for an extra kitchen or bathroom, this can have an impact on the overall price due to more complicated features such as properly installed plumbing.

For a low – mid-range finish you can expect to add around £5,000 for a bathroom or £10,000 for a kitchen.

Bi-fold Doors

These are an increasingly popular addition to a house extension and can be used in a range of configurations from two-door sets to larger, more open plan designs.

They usually cost around £1,500 – £2,000 per door leaf, meaning you can expect to pay an average of £5,000 for a few metres.

Finishings and fittings

It’s very difficult to put an estimate on this as it will, of course, depend greatly on the level of finish that you’re looking for, as well as your own personal taste!

Simple furnishings such as standard flooring painted walls and basic electrical work will keep these costs low, however, if you’re after a more bespoke look with built-in features and fitted joinery you’ll be looking at a higher end budget.

Site constraints

Are there any difficulties or complications your builder may have to overcome in order to complete the project?

These can include necessary demolitions, poor access to the rear of the property for transporting tools/materials/waste, alterations to drainage systems or gas supply, etc. Plus there may be issues to contend with if attempting to lay foundations on clay ground, or if the area is on a slope or surrounded by nearby trees.


Although each house extension project is unique in its design and complexities, with a bit of research and planning you can get a good idea of what your final costs might be.

Start with the basics by considering the average cost per sq/m (£2,000 in London/South East), adding 50% for a double storey. Factor in an additional 20% VAT, professional fees, planning permissions and building constraints.

Then finally add on £5,000-10,000 for a kitchen/bathroom installation, and the costs of other desired furnishings and fittings.

Work with your builder from the start to come up with a plan that covers your needs and an early estimate of additional costs, and you’ll be in a great place to start creating your new house extension!

Live in Essex, including Romford, Brentwood and Upminster looking for a house extension? Click here to find out more and get a free quote.