August 28th, 2025

Building a roof terrace or balcony is a great way to make the most of your home’s outdoor space, a place to relax and enjoy great views. But before you start planning, it’s essential to understand the costs involved. 

 

From structural alterations like knocking through walls and installing French doors, to finishing touches such as flooring, painting, and safety features like glass balustrades, the price can vary significantly depending on materials, design, and contractor choice.

 

In this guide, we break down the average cost of building a roof terrace in the UK, covering basic, standard, and premium specifications, and we also provide cost benchmarks for different regions across the country.

Roof Terrace Cost Calculations

When calculating the cost of a roof terrace on an existing build, there are several additional works to factor in. These often include knocking through an external wall, fitting a patio door, relocating a radiator, laying new carpet and underlay, skimming the wall, and applying a fresh coat of paint. 

 

Our calculations assume that the foundations are already in place, typically above an existing single-storey extension. For safety and style, we’ve calculated the cost using a glass balustrade.

 

In terms of build specification, BuildPartner gives you three broad options to choose from:

 

• Basic spec is a basic finish; e.g., Leyland, Everest, Wickes.
• Standard spec is a standard finish; e.g., Dulux, Hamilton, Slim Line.
• Premium spec is a high-spec finish; e.g., Farrow & Ball, Fine Line, Siemens.

 

In this article, we’ve provided a breakdown of the cost of building a roof terrace to each specification. In addition, we have provided three different benchmarks to show the range of pricing you can expect among different contractors. These are:

• Low benchmark – smaller companies are generally lower cost but less specialised and with low project management function; good for low/mid-spec projects and tight budgets.

• Mid benchmark – medium-sized companies offer a balanced mix of cost-effectiveness and specialisation; good for mid-range projects for effective execution within moderate budgets.

• High benchmark – larger companies generally have a higher cost base but can handle a wide variety of specialist tasks; good for mid/high-spec projects and project management.

 

The specification and benchmark you choose will have a major impact on the overall cost, so it’s important to align them with your budget and the level of finish you’re aiming for.

Cost Of Building A Roof Terrace – Basic Spec

The table below shows the average cost of building a roof terrace to a basic specification:

 

Roof Terrace (Basic Spec)	Total Average Build Cost			Average Cost Per Sq Metre
	Low Benchmark	Mid Benchmark	High Benchmark	Low Benchmark	Mid Benchmark	High Benchmark
East Anglia	£9,831	£10,993	£12,065	£1,639	£1,832	£2,011
Greater London	£10,091	£11,388	£12,282	£1,682	£1,898	£2,047
Inner London	£10,110	£11,372	£11,632	£1,685	£1,895	£1,939
Midlands	£9,529	£10,655	£11,695	£1,588	£1,776	£1,949
North England	£9,872	£11,039	£12,116	£1,645	£1,840	£2,019
Northern Ireland	£9,650	£10,389	£11,688	£1,587	£1,732	£1,948
Scotland	£9,777	£10,933	£11,999	£1,630	£1,822	£2,000
South East	£9,181	£10,208	£11,391	£1,663	£1,849	£2,041
South West	£9,562	£10,854	£11,914	£1,618	£1,809	£1,986
Wales	£9,417	£10,530	£11,262	£1,570	£1,755	£1,877
Average	£9,702	£10,836	£11,804	£1,631	£1,821	£1,982

All costs exclude VAT but include overheads and profits for contractors.

 

Here’s what the data shows for building a roof terrace to a basic specification:

 

• The minimum cost is £9,181, and the maximum cost is £12,282.
• The total average cost is £10,781, or £1,811 per square metre.

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Cost Of Building A Roof Terrace – Standard Spec

The table below shows the average cost of building a roof terrace to a standard specification:

 

Roof Terrace (Standard Spec)	Total Average Build Cost			Average Cost Per Sq Metre
	Low Benchmark	Mid Benchmark	High Benchmark	Low Benchmark	Mid Benchmark	High Benchmark
East Anglia	£10,521	£11,764	£12,912	£1,753	£1,961	£2,152
Greater London	£10,795	£12,159	£13,129	£1,799	£2,027	£2,188
Inner London	£10,831	£12,175	£12,434	£1,805	£2,029	£2,072
Midlands	£10,219	£11,427	£12,541	£1,703	£1,904	£2,090
North England	£10,562	£11,810	£12,962	£1,760	£1,968	£2,160
Northern Ireland	£10,340	£11,142	£12,534	£1,702	£1,857	£2,089
Scotland	£10,467	£11,704	£12,846	£1,745	£1,951	£2,141
South East	£9,816	£10,909	£12,047	£1,778	£1,976	£2,182
South West	£10,252	£11,625	£12,760	£1,733	£1,938	£2,127
Wales	£10,107	£11,301	£12,077	£1,684	£1,884	£2,013
Average	£10,391	£11,602	£12,624	£1,746	£1,949	£2,122

All costs exclude VAT but include overheads and profits for contractors.

 

Here’s what the data shows for the cost of building a roof terrace to a standard specification:

 

• The minimum cost is £9,816, and the maximum cost is £13,129.
• The total average cost is £11,539, or £1,939 per square metre.

 

Cost Of Building A Roof Terrace – Premium Spec

The table below shows the average cost of building a roof terrace to a premium specification:

 

Roof Terrace (Premium Spec)	Total Average Build Cost			Average Cost Per Sq Metre
	Low Benchmark	Mid Benchmark	High Benchmark	Low Benchmark	Mid Benchmark	High Benchmark
East Anglia	£11,743	£13,130	£14,411	£1,957	£2,188	£2,402
Greater London	£11,922	£13,488	£14,630	£1,987	£2,248	£2,438
Inner London	£12,112	£13,601	£13,927	£2,019	£2,267	£2,321
Midlands	£11,444	£12,797	£14,045	£1,907	£2,133	£2,341
North England	£11,785	£13,178	£14,463	£1,964	£2,196	£2,411
Northern Ireland	£11,549	£12,914	£14,174	£1,925	£2,152	£2,362
Scotland	£11,689	£13,070	£14,345	£1,948	£2,178	£2,391
South East	£10,939	£12,193	£13,572	£1,823	£2,032	£2,262
South West	£11,476	£12,993	£14,261	£1,913	£2,165	£2,377
Wales	£11,332	£12,671	£13,524	£1,889	£2,112	£2,254
Average	£11,599	£13,003	£14,135	£1,933	£2,167	£2,356

All costs exclude VAT but include overheads and profits for contractors.

 

Here’s what the data shows for the cost of building a roof terrace to a premium specification:

 

• The minimum cost is £10,939, and the maximum cost is £14,630.
• The total average cost is £12,913, or £2,152 per square metre.

 

Average Cost Of Building A Roof Terrace

So, how much does it cost to build a roof terrace in the UK? Based on the three specifications covered in this article, it costs on average (when using a mid-benchmark contractor):

• Roof terrace – basic spec: £10,836, or £1,821 per square metre. 
• Roof terrace – standard spec: £11,602, or £1,949 per square metre.
• Roof terrace – premium spec: £13,003, or £2,167 per square metre. 

Your final cost of building a roof terrace could be lower or higher depending on the quality of materials you choose and construction methods. 

Please note that the costs outlined in this article assume the foundations are already in place, typically above a single-storey extension, and include:

• Knocking through an external wall
• Fitting a patio door
• Relocating a radiator
• Laying new carpet and underlay
• Skimming the wall
• Applying a fresh coat of paint
• Installing a glass balustrade

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All costs exclude VAT but include overheads and profits for contractors.

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Frequently Asked Questions About Building A Roof Terrace

Here are some answers to frequently asked questions about building a roof terrace.

Are there any security concerns with a roof terrace?

On single-storey properties or where the terrace is easily reached from the ground, it can provide easy access to higher windows or doors when using a short ladder. 

To improve security, fit strong locks on terrace doors and windows, use toughened glass, and consider motion-activated lighting or CCTV. Designing balustrades and barriers to make climbing difficult can also help reduce risk.

Do green roof terraces need special construction?

A green roof terrace usually features a grassy or planted area to create a garden-like space. The roof must be strong enough to support the extra weight of soil, plants, and retained water. 

A high-quality waterproof membrane is also needed to prevent leaks. Not only that, but most green roofs need a drainage system to keep plants healthy and prevent waterlogging. 

How can I increase the privacy of a roof terrace?

One of the simplest solutions is to install privacy screens, which can be made from timber, metal, or other durable materials. You can also use frosted glass balustrades to block views while still keeping the terrace feeling open, airy, and light.

Natural solutions like planters and green walls work just as well, creating leafy barriers that add a touch of greenery. Overhead structures like pergolas or canopies provide shelter while reducing visibility from overlooking neighbouring properties.

Do roof terrace lights need to be waterproof?

Any lighting installed on a roof terrace should be rated for outdoor use, with an IP (Ingress Protection) rating suitable for UK weather. An IP65 rating is usually recommended to protect against rain, wind, and dust. But if you’re installing lights flush with the ground where water might pool, opt for IP67, which is rated for temporary submersion.