Guide to Loft Conversion Prices


In 2016 a survey by the Nationwide Building Society showed that converting a loft can increase the property’s value by up to 20%. But how much does a loft conversion cost and how long does the work take?

Converting your loft from a cold dark storage area to a desirable and habitable living space is, in fact, one the quickest and cheapest ways to add extra room and value to your home.

How much this work costs will depend on the existing roof structure and any planning constraints but use our guide below to give you a rough idea of how much this type of work should cost.

Today a quick search on Google shows loft conversion companies claiming the work can be done for as little as £18,000.

But, how realistic is this price?

Loft conversion prices screenshot

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The question below is entirely optional but we would like to know your answer as we are conducting research into loft conversion prices and how much people think it will cost.

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Is My Loft Suitable for Converting?

This page will reveal the actual price you can expect to pay to convert a loft that already has an acceptable headroom and the height of the finished conversion will not be higher than the original roof.

If your loft doesn’t have enough headroom then the roof will need to be raised or in some cases, the floor below lowered. The cost for this type of conversion is not covered by our price guide. For more complex loft conversions such as these, you will almost certainly need planning permission and a customised price.

For more complex loft conversions such as these, you will almost certainly need planning permission and a customised price.

Measure the Headroom Yourself

Tape measureIf you haven’t done so already, measure the space between the bottom of the ridge timber and top of the ceiling joist.

The bare minimum for a conversion constructed with a dormer should be 2.3 metres and ideally more.

For a loft without dormers, just roof windows, you really need 2.5 metres as a minimum.

What is the Difference Between Planning Permission and Building Regulations?

Planning permission covers how the work will look externally and how it affects the property and any neighbouring dwellings.

Building regulations cover things like fire regulations, safety, ventilation, electrics and plumbing etc.

Is Building Regulation Approval Required?

Yes, all aspects of the build must meet current building regulations and be signed off at various stages throughout the work. For example, the insulation must be approved before the plaster boards are installed.

Is Planning Permission Required?

Planning permission is not normally required. However, permission is required where you extend or alter the roof space and it exceeds specified limits and conditions. www.planningportal.co.uk

Loft plans
About 75% of all loft conversions are covered by “permitted development” rules which allow for work without going down the arduous planning permission route.

For example; a typical semi-detached house outside of a conservation area and with plans for a rear dormer and front aspect roof window would not require permission.

However, a front aspect roof dormer, increasing the roof height beyond original build height, listed buildings or construction in a conservation area would require planning permission.

Framed or Truss Roof


Framed roof structures were used on most properties until the mid 1960’s and are generally more suitable for loft conversions.

Trusses are typically used with thinner timbers and while the prefabrication method results in a faster installation time, they often require additional support during a loft conversion.

Additional support is usually achieved by installing RSJs (rolled steel joints).

Both types of roof structure can be converted but extra supports take more time to install and will add to the overall cost of the build.

Cost of a Typical Loft Conversion

A typical loft conversion could be described as:

  • front aspect roof windows
  • rear aspect window or dormer construction
  • side facing windows (if any) to be obscured glass
  • headroom within existing structure
  • does not overhang original wall construction and walls ideally ~200mm back from roof eaves
  • no balconies or verandas
  • less than 40 cubic metres for a terraced house and 50 cubic metres for semi-detached or detached dwellings
  • the building is not a flat or maisonette
  • the materials used will be in keeping with the original structure

*the cubic metre allowance must include any existing loft conversions.

Project:Price:
Single room, roof windows but no dormer£32000.00
Double room, roof windows but no dormer£35000.00
Double room, shower en suite, roof windows and one dormer£43000.00

Our Guide Price Excludes…

The prices you see displayed in the table above include all labour costs but do not include the cost of the bath, shower, sink, carpets or blinds.

Expect the Loft Cost to Increase if…

Houses with slate roofs tend to cost more to convert than ones with concrete tiles.

Townhouses require extra scaffold at additional cost.

How much work needs to be done to the original building, for example; constructing new partition walls, completely redesigning the layout of the floor below or relocating water tanks to make room for a staircase would add extra cost.

The condition of the existing wiring will need to be inspected and potential changes made such as a new consumer unit or in some cases a complete rewire.

Our experience of home improvement projects is limited to the south-east of the United Kingdom, we believe that prices in central London would be higher, while houses located in regions further north would be somewhat cheaper.

Where Does Your Money Go?

More detail

Below is a more detailed list covering all aspects of a loft conversion:

  • Architect’s fees
  • Structural engineer fees
  • Planning permission fees
  • Building control fees
  • Part wall fees
  • Scaffolding
  • Timber work including floorboards
  • Insulation
  • Plasterboards
  • Dormer construction
  • Roofing felt, leadwork, tiles and vents
  • Windows and roof windows
  • Staircase construction and installation
  • Electrics
  • Plumbing for hot and cold water as well as waste removal
  • En suite items and installation
  • Wall tiles and flooring
  • Doors and trims
  • Painting and sealants
  • Blinds and curtains

The Two Most Common Types of Loft Conversion

  1. a loft constructed without dormers and only roof windows within the constraints of the existing building.
  2. a loft with a rear aspect dormer and front aspect roof windows.

Any type of loft conversion project outside the scope of these two options may cost considerably more than the prices we have suggested.

How Long Does the Work Take?

This depends on the size but 6-9 weeks is a good estimate.

Week 1 – Scaffold erected, materials delivered to site and roof opening made.

Week 2 – Change the structure of the roof and add extra supports if required.

Week 3 – Dormer construction, begin external work and floor joists indoors.

Week 4 – Complete dormer construction and most of the external work Begin plumbing and electrical work.

Week 5 – Install windows, insulation, vents, floor and plaster boarding.

Week 6 to 9 – Bathroom installation, staircase installation, finish electrics and plumbing, door hanging, trims and skirting.

Week 10 to 11 – Decoration.

Get a Firm Quote

We have done our best to research the cost of a loft conversion but our prices are guides and nothing more.

To get a form fixed quote in writing, hit the link below to see how we can help:
Get a Quote Online

More:

We suggest you explore the following websites for official guidance regarding loft conversions:

Planning Portal - loft conversions

Government website - permitted developments

Slough council guide to loft conversions (pdf)

We feel these websites are worth exploring if you are planning a loft conversion:

The loft converting mini guide

An in depth guide to loft conversions by an architect

We feel that this price is not realistic for a complete loft conversion but could apply to the structural aspect of a small conversion.

Some homeowners use a professional firm to carry out the structural work and then complete the remaining work either themselves or by arranging for other tradespeople to do it.

We can only conclude that a price of £18000 is for this type of conversion.

Below you can find a link to our recently updated trade day rates page:

Day Rates For Tradespeople