How to Convert a Loft Into a Room

Completed loft conversion with bedroom and ensuite

How to Convert a Loft Into a Room

If you need more space but love your home, your neighbourhood and your neighbours, then a loft conversion could be the perfect solution.

Loft Conversion – Double Bedroom” by Holland And Green Architectural Design is licensed under CC BY 2.0 .

There are so many associated advantages when you convert a loft. Alongside increasing your living space, you will almost certainly add value to your home, creating room to house a growing family, making a private area for working from home, or even usable space for a new or existing hobby or business.

Loft conversions are usually a more affordable option than a traditional extension, and are a great choice where you don’t have the space to extend. And unlike a garden room, which is another option to create more space, you won’t have to brave the elements to access your loft!

So what should you be aware of when considering a loft extension? What are the options, benefits and challenges? 

What type of conversion should you go for

There are many different types and designs of loft extensions, and your choice will almost certainly be governed by the type of property you live in and what is practical and achievable. Here are several different options to illustrate the variety and potential for loft conversions.

What affects the price?

Loft conversions are not a standard project, so it’s important to choose your builder carefully. Make sure you get three quotes, and these quotes are as comprehensive as possible, detailing all aspects of the proposed job. This will make your choice easier and also alert you to any issues you may need to be aware of for your specific project.

  • What shape is your roof space in? This can be a deciding factor
  • The key purpose for your loft conversion will impact the price. As an example, a simple rumpus room will be cheaper than a master bedroom with a bathroom, or a whole suite of extra loft bedrooms
  • If you need planning permission, listed building consent or other considerations outside the remit of permitted development, this can increase the cost significantly
  • Your geographical location and accessibility of the property may impact the price tag
  • How much work you can do or are prepared to do will also play a role – if you’re a keen and able DIY-er, then there are plenty of areas where you can provide the labour
  • Consider your existing infrastructure and energy efficiency – significant upgrades may be required if you’re adding extra living space requiring heating and plumbing facilities

Dormer Conversion

Probably the most popular and easiest choice, a dormer loft conversion featuring dormer windows is a possibility for most properties and demands the least structural changes. Dormers project in a box shape from the existing slope of the roof, adding headroom and space.

They are usually the most inexpensive option and are generally considered permitted development. The eventual cost will depend upon the property and the design and intention for the space, but as a guideline this loft conversion cost will be between £40,000 – £60,000.  

Mansard loft conversions

A Mansard loft conversion project is often the design of choice for a terraced property. Usually situated at the rear of the house, this option involves raising the wall(s) you share with your neighbour(s) – the party wall – and is a popular choice as it can create both space and headroom. Be aware that you will almost always need planning permission for a Mansard loft conversion.

You will need a larger budget too, with an estimated cost of £60,000 – £80,000.

Velux loft conversions

A Velux loft conversion is ideal if you just want to make better, more habitable use of your roof by adding natural light and ventilation to the loft room and installing roof windows. Also known as skylight loft conversions and roof lights conversions, they are easier and cheaper as they fit into the existing roof slope and don’t require any change to the shape and structure of your roof.

Costs for a straightforward Velux loft conversion will range from £22,500 – £30,000.

Hip-to-gable loft conversions

If you want to maximise available space, then consider a hip to gable loft conversion, ideal for end of terraced houses, semi-detached and detached properties featuring a hipped roof with a sloping side. Here, the loft conversion replaces the slope with a gable wall at the end to add extra head and floor space. Homeowners often also opt for an accompanying dormer loft conversion.

Typical costs for a hip-to-gable loft extension will range from £50,000 – £70,000.

Do you need planning permission for a loft conversion?

In general, if you live in England, you won’t need planning permission – a loft conversion generally comes under the remit of permitted development, unless it is located in a designated Conservation Area, Area of Outstanding Natural Beauty or National Park. However, if your home is a listed building, you will need a listed building consent.

There are some important caveats to this, including how much space you are adding to your home, where this is and how it projects, the height of the extension, incorporation of platforms and balconies, materials and window glazing styles used. It’s always worth checking with your local Planning Office, and applying for a Lawful Development Certificate (LDC) makes sense and will be extremely useful if you plan to sell your home in the future.

In addition, note the Party Wall Act decrees that if your property is semi-detached or terraced, you must notify your adjoining neighbours of your intentions before work begins.

Whatever the style, size and design of your loft conversion, be aware that it will always need building regulations approval.

How to prepare for a loft conversion

So you’re still thinking about converting your loft? Read on!

  • Clear out any items stored in your loft so you and your builders and advisors have a clear view
  • Initial roof space inspection – take a close look at your existing roof space and think about how you want to use it – consult with builders, surveyors and architects to assess the potential
  • Start work on obtaining any necessary approvals
  • Select your builder – get at least three quotes and benefit from their advice and experience, and finalise a contract
  • Remember the impact on your home – water storage tanks and pipework will almost certainly require modifications
  • More structural issues may present themselves, such as the need to remove unused chimney stacks – you’ll need a structural engineer for this
  • Remember that loft conversions add weight, and your foundations may need checking to ensure their suitability to support this new space.

What main activities are involved in a loft conversion?

Most loft conversions are complex challenges requiring different construction processes, materials and activities.

A typical schedule of works will include:-

First Fix

  • Inspections for suitability – initial assessments and recommendations
  • Creation of plans
  • Cleaning and preparation of the space
  • Fitting of new floor joists and all associated tasks involving timber, joist hangers etc
  • Wiring, pipework, roof, wall and floor insulation, roof and soffit vents
  • Installation of floorboards
  • Installation of dormers and/or roof lights and vents
  • Access considerations – staircases
  • Installation of partition walls with CLS timber stud work
  • Drywall plasterboarding
  • Upgrades to existing plumbing system and electrical system
  • Decorating

Second Fix

  • Skim coat plastering, architraves, skirting boards
  • Installation of sanitaryware where required
  • Decorating

Asses whether the space is suitable

To be suitable for a loft conversion, head height is important; the usable section of the loft space should be at least 2.2m. Measure from the bottom of the ridge timber to the top of the relevant ceiling joist below.

If the measurement is less than 2.2m, a loft conversion may still be possible, but you will need to either raise the roof – a complex and costly task requiring planning permission – or lower the ceilings in the rooms directly below.

Roof pitch is an important consideration too; the central head height will be higher if your roof is more steeply pitched. Adding a dormer will increase the potential floor area.

Building a staircase to the space

Access to your loft conversion is an important consideration, as you don’t want to lose too much space on the storey below, but equally don’t want to create a staircase which presents access issues for people and objects.

A purpose-built loft conversion staircase will be significantly more expensive than an off-the-shelf option and should be approved first by Building Control.

There are fire safety and fire protection implications too – stairways are supposed to lead to a hall and external door. If your layout is open plan, you may need to create a partition wall and also consider fire doors and escape routes in the event of a fire. Fire safety also requires a linked fire alarm system with mains-powered smoke alarms for the entire house.

There are additional building regulations requirements for staircases involving the number of steps, step sizes and balustrading, and your staircase may require a timber framework.

Assess and improve roof structure and joists

The majority of cut and pitched roofs involve rafters and purlins supported by internal struts located in the loft space. For a loft conversion, these internal struts need to be removed to make unobstructed room for the new loft space.

In addition, the existing ceiling joists from the floor structure below are unlikely to make adequate floor joists to comply with building regulations, so additional, stronger new floor joists will need to be fitted alongside. These will either span between external and internal load-bearing walls, or it may be necessary to install new beams to support them, and joist hangers will require replacement.

For smaller loft spaces and conversions, a dwarf timber stud wall known as an ashlering may be constructed to support the sloping rafters, enabling the removal of the internal struts and braces.

Fit windows

Bringing in the maximum amount of natural light will probably be an important consideration for your new loft conversion. Rooflights and skylights are relatively easy to accommodate, whereas dormer windows will require walls and a roof to be in place.  Dormers to the front of a property require planning permission.

Dormers maximise head height and add space, but are more complex structures and need to be supported at the ridge with a ridge beam.

Construct stud walls

Interior stud walling is usually constructed as partition walls or batten walls using CLS (Canadian Lumber Standard). CLS is straight and consistent and provides a reliable and affordable choice for stud walling and concealment applications, for example, cisterns.

Add electrics, lighting and heating

All electrics must comply with Part P of the building regulations and also to the 17th Edition Electrical Regulations. Employ an appropriately qualified electrician to carry out the work and make sure you get a certificate of compliance when it’s done.

It may be necessary to fit a new consumer unit and other elements to bring the electrics in line with requirements.

Insulating the space

The increasing focus on energy efficiency for buildings means that loft conversion insulation is now a more complex consideration, involving either cold roof insulation or warm roof insulation. If you’re replacing the roof, then you can fit insulation between the rafters and the roof itself, which is a great solution.

If you are retaining the existing roof structure, then insulation must be fitted between the rafters. Here, choose a high-performance insulation such as a foam board for optimum results. This should also be used around dormers and ashlaring walls.

Floors and walls require insulation too. For the floor, insulation is usually laid between the joists. Internal partition walls require sound insulation as well as heat insulation, and party walls can be insulated by installing timber studwork with the insulation hidden beneath the sound-rated plasterboard. Requirements for your property will be covered by building control regulations.

How long does a loft conversion take?

This will be dependent upon the design and complexity of your loft conversion design; if structural reinforcements are required, then the work on-site will take longer. As a general guideline, loft conversions usually take anything between six and twelve weeks.

Does a loft conversion add value?

Which? Magazine states that “A well-designed loft conversion can add up to 20% to the value of your home.” How to plan a loft conversion – Which?

The actual increase in value from more useable space is dependent upon several factors. Geographical location is an important issue; generally, homes in the south of England see a greater increase.

The purpose of the newly converted loft is also a consideration. Adding a luxurious ensuite master bedroom loft conversion commands the greatest returns.


If you’re considering a loft conversion for yourself or are buying materials for a loft conversion for a client, then Supreme Merchants offer a comprehensive range of building supplies, available ex-stock, and delivered nationwide.

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