Which is right for me? A loft conversion or an extension?

20 Mar 2025

If you're deciding between a loft conversion or an extension, this blog covers the basics, the benefits, and cost comparisons.

Stephen munley Vdahehd Mfl0 unsplash

When deciding between a loft conversion or an extension in your next home improvement project, it’s important to get clear on the basics:

  • What is the purpose of your expansion?

  • Would this project work in your current home?

  • What is your budget?

First of all, identify what the purpose of your expansion is:

  • Do you want to add another bedroom or study?

  • Are you hoping to enlarge your kitchen or living space?

  • Do you want to make better use of existing space?

  • Do you want to add the most resale value possible to your home?

Getting clear on the reason why you want to expand your home will be the first step in deciding whether a loft conversion or an extension will work better for you.

Secondly, assess the current structure of your home to determine whether or not the expansion is feasible.

For example, if you’re hoping to convert your loft, you’ll need to establish whether or not it has sufficient headroom for the space to work as a functional room.

Finally, establish your budget. This will determine which project is more cost-effective, the quality of contractors and materials you can afford and other variables.

Benefits of Loft Conversions vs Extensions

Loft Conversions Benefits

Increased energy efficiency: A surprising benefit of loft conversions is the increased energy efficiency within your home. Since you’re building on the existing roof of your house, you’re reinforcing the insulation as a result.

Less Disruption: Since loft conversions occur at the top of the house, the building work is relatively contained to a single room; meaning less disruption for you and your neighbours.

Space Optimisation: Loft conversions make use of existing space within your home, meaning you won’t need to sacrifice part of your garden or the surrounding areas of your house.

Extension Benefits

Increased Customisation: An extension gives you much more freedom over the design, since you’re not confined to a specific shape or size.

Increased Functionality: Extensions provide much more flexibility in terms of what they could become: whether you’re increasing existing living spaces or adding entirely new rooms into your home.

No space constraints: You don’t need to check whether or not your space has enough headroom to work as a functional room, unlike loft conversions.

Cost Comparisons and Planning Considerations

Cost Comparisons

Like most building projects, the cost depends on several factors: size, complexity, location of your property, contractors and the type of conversion or extension.

On average, building an extension is typically more expensive than a loft conversion (but this of course varies based on your independent circumstances).

For the average loft conversion, you should expect to pay anywhere between £30,000 and £75,000.

For the average extension, you should expect to pay anywhere between £2,000 and £3,200 per square metre, depending on quality of finish.

Planning Permissions

For loft conversions, it’s unlikely you’ll need to obtain planning permission to start work as your loft is within your permitted development.

That being said, there’s likely to be certain limitations on the conversion, including: size, height and materials used.

Before you start work on your loft conversion, double check with your local planning authority and ensure that you’re compliant with your building’s safety regulations.

Whether or not an extension requires planning permission depends on the type of extension you’re hoping to construct.

As a general rule of thumb, much like loft conversions, if your extension falls within your permitted development, you don’t need to apply for planning permission.

Here’s some examples of when you’ll likely need to apply for planning permission:

  • Your extension exceeds the height of the existing structure

  • You’re planning a two-storey extension to the side or front of the existing structure

  • The materials differ from the aesthetic of the existing structure

Always conduct detailed research on whether or not you need planning permission before you start work on your extension or loft conversion, check in with your local authority and ensure you’re compliant with your building’s regulations.

What adds the most resale value?

Typically, the loft conversion adds more resale value than the extension; though both can add significant value to your property under the right conditions.

Nationwide, a well executed loft conversion can add anywhere between 10-20% resale value to your property. In built-up areas where space is harder to come by, such as London, this number could increase.

By “going green” and installing eco-friendly roof windows, for example, you may be able to snag a further 5% value-add from more environmentally conscious buyers.

Ultimately, the value of your loft conversion or extension depends on factors such as:

  • Type: are you adding another livable room?

  • Quality: are you employing contractors or doing it yourself?

  • Market Conditions: what’s the current state of the housing market?


Final Thoughts

Both a loft conversion or extension are exciting and valuable projects to undertake in your home. Ultimately, which is better for you depends on:

  • Your reason for expanding your home

  • Your budget

  • Your resale value goals

Whichever project you choose, ensure you enlist the help of a CPA-registered tradesperson for a reliable and quality finish.


Photo by Stephen Munley on Unsplash


Screenshot 2024 05 07 at 14 17 16