Costs & Guides

Are you wondering whether to build an addition or a loft conversion? Our guide will explain which will give your property the greatest space and value.

When deciding whether to build an addition or a loft conversion, there are numerous aspects to consider. Both projects, obviously, provide homeowners with the opportunity to add usable more space to their houses without having to relocate — and each can add significant value if done well.

We’ll go over the following topics in this guide:

• Whether you do a loft conversion or build an extension, you will increase the value of your home.
• Costs of a loft conversion vs. an extension
• Each route’s planning approval requirements
• Which one will look best in your home?
• Which is more disruptive: a loft conversion or an extension

What is Cheaper to Build, an Extension or Loft Conversion?

When compared to extensions, loft conversions are a very cost-effective option to add extra room to your house. However, depending on the complexity of the job and the type of loft conversion you’re doing, these expenses can quickly escalate.

A basic ‘rooflight loft conversion’ with a double bedroom, for example, may cost between £18,000 and £25,000. However, if you upgrade to a dormer loft conversion, the cost might be closer to £40,000, while a modular or mansard loft conversion could cost £65,000.

So, how much does it cost to get an extension? It’s difficult to give a precise figure for extension prices because the amount you pay will be determined by the size, location, and style of your extension.

In general, however, the majority of extension projects cost between £1,350 and £2,250 per m2. Work on a budget of £1,350-£1,750/m2 for single story extensions, and £1,250-£1,650 for two storey extensions.

For both loft conversions and extensions, you will also need to factor in additional costs, including:

• Design fees
• Surveys
• Planning permission costs
• Building regulation fees
• Insurance
• Party wall agreements
• Structural engineer fees

What Adds More Value, an Extension or Loft Conversion?

It’s quite difficult to estimate how much value an extension will bring to a home; the size and location of the extension, as well as the sort of space it adds, will all play a role.

You must also consider the ceiling price of houses in your area — that is, the maximum value of properties in your neighbourhood. It’s advisable to contact with local estate agents, who should be able to estimate the value increase that an extension could provide.

Kitchen extensions, on the other hand, can add 5-10 percent to the value of your home, while an extension that adds an extra bedroom can add up to 20-25 percent.

When it comes to predicting how much value a loft conversion will contribute to a property, it’s difficult to give an accurate figure, just as it is with additions. However, if you add an additional bedroom with an en suite to your loft conversion, you can expect a value increase of 20-25 percent, assuming the loft conversion was completed to a high degree.

Expect a lesser value rise of roughly 10% in the event of a new home office.

Before you get too excited, keep in mind that in order to achieve these increases in value, you’ll need to think about how you’ll provide additional storage space elsewhere in the house once you’ve removed the storage that a loft previously provided.

Will an Extension or Loft Conversion Suit My House Better?

When deciding between a loft conversion and an extension, consider which way of adding extra space will work best for your property.

Loft conversions aren’t appropriate for every type of home. This is due to a number of factors. Some homes lack loft space (for example, those with vaulted ceilings), while others lack sufficient headroom – you’ll need at least 2.8m of unobstructed vertical space. In other circumstances, there will be insufficient space for the additional staircase, or planning approval will be denied.

While many of these challenges can be overcome, you must examine how any additional costs incurred as a result of these concerns will effect any potential profit.

Before making a decision, check to see if your loft is suitable for conversion.

Most properties, on the other hand, will benefit from extensions. For people who live in terraced or semi-detached homes, side return extensions, as well as rear extensions, can be a terrific alternative. Single storey back extensions or wraparound extensions are a fantastic way to create a larger, more social kitchen diner, while two storey extensions are a cost-effective option to add living space on the ground floor and an extra bedroom on the second floor.

The most important consideration is how much of your outside space your new extension will eat up, as well as how much value it will add in relation to your costs.

You must also consider planning approval requirements for larger extensions and loft conversions that do not come under Permitted Development.

Will an Extension or Loft Conversion Add More Space?

When compared to an extension, the amount of extra room you can add with a loft conversion is usually limited — but this will obviously rely on your outside area and planning approval constraints. A loft conversion may be the only method to acquire extra space internally for individuals who have little or no spare yard space.

Is It Easier To Get Planning Permission For an Extension or Loft Conversion?

Loft conversions and extensions may not usually require planning authorization.

Loft Conversion Planning Permission:

Loft conversions are frequently covered by allowed development rights. However, in order for this to be the case, your loft conversion must not have the following features:

• To the current roof space, add more than 40 cubic metres for terraced buildings and 50 cubic metres for others.
• Under PD rights, exceed the height of the existing roof.
• On the main elevation, extend beyond the existing roof slope.
• Include raised platforms on any verandas or balconies (Juliet balconies are allowed).

Furthermore, your property’s Permitted Development rights must not have already been used to create a second story. Your PD rights will be affected if you live in a designated location, such as an Area of Outstanding Natural Beauty.

Planning Permission for Extensions: 

Planning authorization is not required for all additions. Some will come under approved development, just as loft conversions. The following factors will influence whether or not your extension is considered permitted development:

• Single-story extensions that extend more than 4 metres from the back of your property will require planning clearance for detached properties. This is above 3 metres for terraced and semi-detached dwellings.
• Prior Approval is required for extensions of 8 metres (for detached dwellings) and 6 metres (for semi-detached houses).
• The extension can’t be bigger than half the size of the original house’s lot (as it stood as of 1948)
• Planning permission may be necessary if the materials used in the addition are visibly distinct from the remainder of the property.

• Two-story expansions must be no closer than 7 metres from the property line.
• Permission is required for front extensions, which are those that are located in front of the main or side elevations and front a highway.
• Permission will be necessary if the maximum height of your single-story extension exceeds 4 metres or is higher than the highest point of the roof.
• Planning authorization is required for balconies or verandas.

Is a Loft Conversion or Extension Less Disruptive?

Loft conversions are generally faster and less intrusive than extensions. This is not always the case, though. In order to add a modest bedroom or home office, a simple loft conversion to a space with lots of headroom might take as little as four weeks. A modular loft conversion to create an en suite bedroom or one that requires the floor to be lowered, on the other hand, may cause significant disturbance and take up to 16 weeks.

Similarly, a tiny back extension that can be shut off while work is done is unlikely to cause significant disturbance, whereas one that includes significant internal remodelling will. A simple, single-story extension could take two to three months to complete, while bigger, two-story extensions could take six months or more.