23 Reasons Why Loft Conversions Are So Expensive




why are loft conversions so expensive?

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Loft conversions are one of the most expensive home improvement projects as they involve major structural changes to your home. There are also many additional costs such as professional fees, planning applications, and materials.

Of course, the major expense will be the specialist builder you employ to build your loft conversion. But within their quote there will be hidden costs and there will also be other expenses not covered by your builder.

Reasons why loft conversions are so expensive

1 – Structural changes
2 – VAT
3 – Planning fees
4 – Building control fees
5 – Party wall agreement
6 – Bat survey
7 – Location
8 – The economy
9 – Type of roof
10 – Dormers
11 – Architect fees
12 – Plumbing

13 – Underfloor heating
14 – Electrical
15 – Materials
16 – Storage
17 – The stairs
18 – Terrace, semi, or detached?
19 – Bungalow
20 – Plastering and decoration
21 – Insulation
22 – Finishing touches
23 – Furnishings

Structural changes

The biggest cost of all. Adding an extra story to your home is obviously going to have a major impact as the existing joists won’t support a new floor. The extra steelwork and structural changes to the roof are the biggest and longest job of the whole project. And with the internal preparation, steelwork, and alterations to the roof probably account for around £10,000 of your budget.

Needless to say, this is when you will experience the most disruption, but there’s no getting away from it. The time the structural changes take will depend on whether you’re having roof lights or a dormer built.


This is a pain in the wallet. Most if not all the contractors you use for your loft conversion will be VAT registered. This means you’re going to have to pay an additional 20% on most of the labour and material cost of your project. That £30K loft conversion has just gone up to £36,000.

Planning fees

Most loft conversions do not need planning permission. This is because they are classed as permitted development. Nevertheless, there are instances where you will have to apply for planning permission; if you live in a conservation area, if your property has been extended before, and if the loft conversion will be built above the existing roofline.

In these instances, then you will have to apply for planning permission and that process can cost over £1,000 depending on your local authority and complexity of the application.

Read this article for more information: Do Loft Conversions Need Planning Permission?

Building control fees

No getting away from these fees. Your loft conversion must comply with the building regulations and you must get building approval before and after your project.

Again, the amount you pay for your application will vary from council to council or whether you use an independent inspector, but expect to pay between £500 and £1,500.

For more information check out this article: What are the Loft Conversion Building Regulations?

Party wall agreement

If you live in a semi-detached or terraced home your loft conversion will impact neighbouring properties. Builders will often lay the new steel beams from party wall to party wall so you need to comply with the Party Wall Act.

This involves giving your neighbour advance notice of the work you intend to complete and you must reach a party wall agreement with them. Hopefully this will be straightforward but your neighbour can raise a dispute.

Although this dispute can’t stop your loft conversion from going ahead it can result in extra costs.

You have to pay for your own surveyor and if the neighbour raises a dispute you have to pay for their surveyor too. As you can imagine this can get expensive and you could be looking at fees of between £1,500 and £3,000.

You can learn more from this article: Do I Need a Party Wall Agreement for My Loft Conversion?

Bat survey

Wait. What? Ok, you’re going to be very unlucky if you get stuck with this but don’t discount it. Bats are a protected species. If you have bats nesting in your roof, and there is a surprising number of instances when this has been the case, you must have a bat survey done. And naturally enough, you must pay for it.

A bat survey can cost up to £800 but you must get it done. Bats won’t stop your loft conversion going ahead but you do need a licence to proceed with the work. And you can’t get that without having a survey done.


Where you live in the UK influences how much you will pay for your loft conversion. There is a definite north / south divide in the UK when it comes to costs and. If you live in the south east, you will pay around 20% more (at least) then someone who live in the north east for a similar loft conversion.

London is undoubtedly the most expensive place in the UK when you are converting the loft. Which I’m sure won’t come as a surprise to anyone.

The economy

Inflation, recession, rising prices – however the economy is performing will affect the cost of your loft conversion. Wages are frozen leaving us with less real income, interest rates may mean it’s more expensive to pay for your project, and even shortage of materials will force prices up. As anyone who was trying to convert their loft following the lockdowns will know.

Type of roof

Most lofts in UK properties can be converted, but some are much more complicated jobs than others. A mid-sixties terrace will usually have a large loft which is easy to convert but an inner London home may have a mansard style roof which is anything but easy to convert.

Similarly, if you live in a detached property, you may need a double hip to gable conversion will increase your costs and make your loft conversion much more expensive than a dormer on a terrace.


If you need to create extra headroom in the loft, you’ll need to build a dormer. The dormer is built up from the roof slope to make the additional headroom you need. But of course, this comes at a cost.

A dormer loft conversion involves more structural work then a Velux conversion and so you will pay far more for this type of project.

Architect fees

It’s always a good idea to have full plans drawn up. Especially if you’re building a dormer or have a complicated build like a mansard loft conversion. You can of course have the plans drawn up before you look for builders which will give a great handle on what the build will entail.

Some builders will include plans in their service but if you hire your own architect you can expect to pay a few hundred pounds for very basic plans but a full architect service may cost around £2K.


Part of the reason why loft conversions are so expensive is the plumbing work which must be done. Properties with an older boiler will need it replacing as it won’t be able to cope with the increased demands of an additional floor to the property. Older properties will also need their water tank taking out or relocating which also adds to the overall cost.

And if you are creating a new bedroom in the loft then you’ll more than likely want an en-suite bathroom too. This is where it gets expensive as a new bathroom could add as much as £5,000 to your overhead.

Underfloor heating

Radiators have been the usual solution for heating loft conversions but underfloor heating is gaining in popularity. It’s far more energy efficient, straightforward to install, and importantly it frees up the space that bulky radiators take up.

Of course, there are additional costs involved and an underfloor heating system will probably add around £1,500 to the final cost of your loft conversion.


You’ll need to pay a sparky to do all your electrical work. Electricians are at the higher end of the contractors’ hourly rate table so the more electrical work you need the more the costs will add up but will probably top out at around £2,000.


The cost of raw materials can vary around the country and are also at the whim of the economy as we mentioned earlier. With a loft conversion your builder will use a lot of timber and steel so price fluctuations can affect how much you end up paying.


When you convert the loft, you gain lots of living space, but lose all that convenient storage. But you can still include plenty of storage solutions in your new space but you will need bespoke furniture.

Built-in and eaves cupboards are elegant ways of making extra storage and builders now are adept at fitting ingenious storage solutions into even the smallest of spaces.

Of course, there are more costs involved and thousands of pounds could be added to the final cost especially when you have bespoke storage made for you.

The stairs

Locating the stairs is one of the most important elements of a loft conversion. But the cost of building and installing stairs varies widely depending on the style of staircase you decide to install.

Most of us will go for a standard staircase but costs can quickly escalate if you want something different. Custom built stairs will be around twice as much as a standard staircase but if you want something like spiral stairs you could be looking at as much as £10,000.

Terrace, semi, or detached?

The type of property you live in will affect the final cost of your loft conversion. Converting the loft of a detached house will cost more than a semi-detached, with a terraced house conversion costing less than either.

With a detached property the rear slope of the house will often be rebuilt as a gable end to allow a dormer to be installed. All this structural work adds to the cost which is why detached loft conversions are so expensive being around £10,000 more compared to a semi-detached.

For semi-detached and terraced properties installing roof lights is the simplest and cheapest option though dormers can be built on either type of property.


Adding an extra story to a bungalow with a loft conversion is an obvious attraction for many homeowners. The added space can be used for bedrooms or an upstairs living area.

Because bungalow lofts tend to be larger than those on other properties they do cost more and, as the building was never intended to support two levels of living rooms, there will also be extra structural costs.

Plastering and decoration

When you get to this stage the end of the project is in sight but unfortunately the end of the spending isn’t. Plastering and decoration all add to the final cost and with labour fees of up to £50 an hour the final tally keeps rising. You could save costs by doing this work yourself but if you’re unable to do so you may need to hunt around for more affordable contractors.


Needless to say, your new loft conversion needs to be properly insulated. The different types of insulation will impact on your costs with sheet insulation costing twice as much as blanket insulation. With any building project energy efficiency is important, but especially so when you’re working in the loft. To learn more, you can read this article: Are Loft Conversions Energy Efficient?

Finishing touches

Don’t forget to include flooring and materials such as paint into your budget. Some builders will include the finishing touches in their quote but most won’t.

As an example of how the finishing touches can impact on the cost of your loft conversion, consider the flooring. If you opt for tiling the floor it’ll cost four or five times as much compared to laying carpet.


Not a component cost of the loft conversion itself but once the build is finished you do need to furnish it. Which is the fun bit but don’t forget to budget for new beds, furniture, fittings etc when you do your initial planning.

How much does a loft conversion cost anyway?

As we’ve seen the expenses can mount up, but the final cost of your loft conversion will depend on a whole range of factors from where you live to the type of roof you have or even whether you have bats in the belfry (or rather the loft).

All that said, you could pay as little as £27,000 or as much as £80,000. We’ve covered this in more detail with a breakdown of average costs in this article: How Much Does a Loft Conversion Cost?

A final thought

Yes, loft conversions are expensive. There’s no getting away from that. But converting the loft will not only increase the living space in your home but it could also add up to 15% onto the value of your property. So even though loft conversions are so expensive they can be well worth doing.

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