How to plan a loft conversion

It can be difficult to know where to start when planning a loft conversion.

From deciding whether to go for a dormer, mansard or rooflight conversion, to figuring out planning permission and hiring a team to do the work, there's a lot of choices to make.

But it doesn't need to be a complicated journey. Read on to discover how to plan a loft conversion.

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Loft conversions step-by-step

There are five key steps to follow when planning a loft conversion: 

1. Work out your budget - including contingency costs: Before you start any renovation you should always work out what you can comfortably spend. Include at least 10% on top of your predicted spend to cover any unexpected costs. Read our guide to loft insulation costs to see how much you can expect to spend on different types of conversion. 
2. Find out if you can convert your loft: You'll need to consult an engineer for this step, but there are a number of checks you can run yourself. Jump to Can my loft be converted? 
3. Decide which type of conversion will work best: Depending on your budget and needs, you can opt for anything from a simple rooflight conversion, all the way up to a mansard conversion. Jump to Loft conversion types.
4. Check if you need planning permission: Many loft conversions can go ahead under permitted development, but larger scale conversions will require planning permission, and all conversions are subject to building regulations. Find out more in our guide to loft conversion planning permission and building regulations.
5. Choose a builder or architect: The best place to start is to speak to a friend or neighbour who has been through the process and get their recommendations. You can also read our advice on how to find an architect or builder for an extension.

Can my loft be converted?

Before you do anything else, you need to work out whether your loft space is suitable for a conversion.

You can ask a builder, architect or surveyor to visit your home and check this out for you, but there are a couple of assessments you can carry out yourself:

• Measure the head height: You'll need a minimum ceiling height of 2.2 meters in order to convert your loft.
• Look for other conversions on your street: If similar houses on your street have loft conversions, it's a good indicator that you can convert your loft as well.
• Work out if your building is protected: If you live in a listed building or an area of outstanding natural beauty, it will be much harder for you to get permission to convert your loft.
• Make sure you can create an access point: You will need to ensure there is space for a staircase leading up to your loft. 

Read our guide to loft insulation costs and savings

Types of loft conversion

There are four different types of loft conversions: rooflight, dormer, hip-to-gable and mansard. The one you choose is likely to be determined by a number of factors, including the type and age of house you live in, as well as your budget.

Rooflight loft conversion

• Pros An affordable option for buyers on a budget, suitable if you live in a conservation area.
• Cons Offers far less space compared to a dormer or mansard conversion.

Rooflight conversions are by far the cheapest and least disruptive option, as you won't have to make any changes to the shape or pitch of the roof. Instead, it's simply a case of adding in skylight windows, laying down a proper floor and adding a staircase to make the room habitable.

However, you'll need to have enough roof space without an extension for this type of conversion.

Dormer loft conversion

• Pros An option for most houses with a sloping roof.
• Cons More structural changes needed compared with a standard conversion, so can take a while to build.

A dormer loft conversion is an extension that protrudes from the slope of the roof. Dormers, in particular flat-roof dormers, are the most popular type of conversion. They're suitable for almost any home with a sloping roof. 

Dormer conversions are less expensive than mansard or hip-to-gable conversions, but will still add a good deal of extra headroom and floor space.

Hip-to-gable loft conversion

• Pros Generally less expensive than extending outwards and more natural-looking compared with a dormer conversion.
• Cons More expensive than a dormer conversion, only suits houses with a free sloping side roof.

Hip-to-gable conversions work by straightening the sloping 'hipped' roof at the side of your property to create a vertical 'gable' wall, creating more headroom in the loft. This type of conversion will only work on detached, semi-detached or end-of-terrace houses, as it requires a free sloping side roof. 

If you have a detached house with sloping roofs on either side, you can build on both to create an even more spacious double hip-to-gable extension.

Mansard loft conversion

• Pros Creates lots of new useable space, suitable for many different types of property.
• Cons Can be particularly expensive, doesn't look very natural due to the change in roof slope.

Mansard extensions run along the whole length of your roof and will alter the angle of the roof slope, making it almost vertical. These tend to be the most expensive type of conversion, but will result in a significant amount of extra space. 

Mansard conversions are suitable for most property types, including terraced, semi-detached and detached houses.  

Find out more about any permissions required in our guide to loft conversion building regulations and planning permission

Loft conversion ideas

Remember that any room that requires plumbing or a lot of floor space will be more labour-intensive - and therefore expensive - than simple conversions. 

Here are some loft conversion ideas:

1. A principal bedroom suite: Creating a new principle bedroom with an en suite typically generates the greatest return on investment for a loft conversion. However, it does require a lot of work, particularly installing the bathroom, and you'll need a decent amount of floor space. 
2. Home office: With many people now hybrid working as standard, adding an office space to your home can offer a good return on investment. It doesn't require very much space, but you will need to ensure you get good wi-fi in your loft. You may wish to consider a wi-fi mesh system - find out more in our guide to the best wi-fi extenders and wi-fi mesh systems. Check out our home office ideas, too.
3. Home gym: It's unlikely you'll be able to add a full gym to your loft, but if you want a quiet space for a treadmill or exercise bike, this can be a great choice. 
4. Non-habitable loft conversion: Don't forget that you can simply convert your loft into an open storage space. Non-habitable conversions can free up a lot of space in the rest of your home, and rarely require planning permission. They also need to adhere to fewer building regulations.  

Loft conversion stairs

A staircase may not be the first element that comes to mind when planning a loft conversion, but it is one of the most important.

Many people neglect to factor in changes to the floor below the loft when planning a conversion, but it's worth having a think about where the staircase is likely to go and how much room it might take up.

Even a well-designed, space-saving staircase could take up a sizeable chunk of a room, so make sure you have space you're happy to lose. Consider the flow of your home and remember – you'll need to carry furniture up to that room.

Expect a customised staircase to be at least five times more expensive than a standard one.

Think about:

• Headroom: Check whether you have enough space for the staircase and loft conversion. 
• Location: Where you can place the stairs and if the location will require an alternating tread staircase or spiral staircase.
• Step height: Regulations stipulate a particular pitch or angle for your stairs and the riser of each stair also has minimum requirements.
• Fire safety: You'll need a protected escape route and a linked fire alarm system for the whole house.

Insulation is also an important part of your conversion - find out more in our guide to types of loft insulation 

Other loft conversion considerations

Working with an architect

Unless you are a professional, you should always consult a structural engineer when converting your loft, to ensure it is safe to use. 

However, you may choose not to work with an architect (who will focus on the design of your conversion), if you are confident you can design a functional loft conversion yourself.

With that being said, working with an architect can offer a number of advantages, and even end up saving you money in the long-term. Not only will they help to oversee the whole project, they can ensure the project is as efficient as possible, and advise you on the designs which will offer the best return on investment

Loft conversion storage

Loft conversions can help you to create more storage space in your home. 

However, if you already use your loft for storage, you should bear in mind that converting it to a living space will dramatically reduce the storage capacity. 

You can maximise storage in your loft by opting for built-in furniture, which will create space in awkward corners (under the eaves or sloping ceilings, for example). 

Consider also multi-functional furniture, like beds with built-in drawers. 

Should I tell my home insurance company about a loft conversion?

Yes, you should tell your insurer about any changes that will alter your home’s structure, habitability, security or value. For example, a loft conversion may increase its value and this will likely affect your buildings and contents insurance premiums.

If you are staying elsewhere while your loft conversion is completed, you should tell your insurer about this and try to give several weeks’ notice.

In instances where you’re having serious building work done, consider specialist renovations insurance. This covers against things going wrong with the building work, materials and property owners’ liability.

How long does a loft conversion take?

Ultimately, the answer to this question depends on the trader you're using and the type of loft conversion they're dealing with.

• Rooflight loft conversions are usually the quickest, taking around four weeks to complete.
• Dormer loft conversions can take closer to five weeks.
• Hip-to-gable loft conversions can take around seven weeks.
• Mansard loft conversions will be closer to eight weeks to complete.

The first week or two will be spent preparing your home and gathering the materials and tools required. 

Work usually starts on the outside of your property. After that, the focus turns to the inside of your house and the flooring, insulation and stud walls. The final stage will deal with plastering, electrics and plumbing.

Discover the best and worst home insurance according to our research

Top tips for a smooth loft conversion

Some hiccups over the course of your loft conversion are unavoidable, but there are a number of things you can do to keep these to a minimum and avoid any nasty surprises. We've compiled some key expert tips to help you get prepared.

• Do your research: It's best to be as clued-up as possible, so you know what to expect and can be really clear about what you want – from how you will use your conversion to how it will look.
• Budget carefully: Make a thorough budget and then factor in around 10-15% extra for contingency costs, in case something goes wrong.
• Prepare for disruption: Bear in mind that the conversion may impact your whole home (for example, you may need to relocate a water tank from the loft or get fire doors fitted).
• Make a schedule: Once you have scheduled any structural work, remember to add time for any additional jobs, such as painting and decorating.
• Keep your neighbours on side: Set their expectations by agreeing start and finish times, and letting them know when certain parts of the building process will happen. Getting them on your side will be particularly useful if you need to get a Party Wall Agreement, which applies if your loft wall is shared with the neighbour – this can be a lengthy and costly process if they're not happy with the plans.  

Loft jargon buster

Builders finish

Typically, a builders finish involves fitting plug sockets, light fittings, skirting boards, architraves and plastering the walls. It's unlikely to include jobs such as decorating, tiling or carpeting.

If your building firm says that it will complete your conversion to a builders finish, it's worth double checking exactly what's included.

Pitch

The pitch of a roof simply means its steepness.

Some types of loft extensions, such as mansard conversions, work by altering the pitch of the roof to create more space internally.

Rafters

Rafters are the sloping beams inside your loft that support the roof.

If you have rafters, as opposed to roof trusses (see below), your loft should be easier to convert.

Roof trusses

Roof trusses are timber frameworks that span the cross-section of your loft space and support your roof.

Typically, roof trusses will make a loft trickier to convert than old-style rafters and could double the cost of your extension.

Shell conversion

Shell conversions are part conversions, where the structural work is carried out by a building firm but the rest is left to you.

Usually, a shell conversion involves completing all structural timber work, creating a watertight internal loft space and fitting windows and doors, chipboard flooring, a staircase and any internal stud walls.

Velux

Velux is a popular brand of skylight that has become synonymous with roof-light windows.

A Velux conversion simply involves fitting Velux rooflights, and is suitable only if your loft is already the right size and meets building regulations.