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Loft Conversion Step-By-Step Guide. How To Convert A Loft?

loft conversion design ideas

A lot of homeowners around London want to add value to their property and increase the quality of living within their property. The only dilemma a homeowner may face is – how to do it. Here we aim to show you the ins and outs of converting your loft space into a suitable living space and hopefully, show you why you can’t afford to leave that space empty.

When you start the process, the first thing you should consider is what type of conversion will you go for…?

The Room In The Roof…

The most affordable options are Velux windows on the roof, reinforced flooring, insulation, heating, electricity, fire safety, and a staircase… this is the basic starting level of a loft conversion. With this option, there is generally no planning permission required because it will be covered under permitted development as you are not building outwards from your property, but you should always check that with your local authority. This can be a great option to add that extra bedroom for the teenagers in your home to finally get their own room, or you can go outside the box and indulge in a family home cinema. These conversions tend to carry a cost of around £1500 per square meter, not including VAT and fees, of which will be covered later.

To Dormer, Or Not To Dormer…

In our experience, a dormer conversion can really divide opinion, in terms of the aesthetic impact that it has on your home. You may also require planning permission, particularly if your property is in a conservation area. But the payoff is the extra light and the significant increase in height and subsequent volume within your new loft room. This can be the difference between a new kid’s bedroom and a master bedroom with an en-suite bathroom. Going this route with the extra en-suite could mean your conversion adds a juicy 25 – 35% of value to the property. Needless to say – the added convenience of having the extra shower, bath, and toilet in a family home could be priceless.

Upgrade The Structure Of The Roof…

Alternatively, you can alter the structure of the roof, along the lines of a hip to gable roof extension or a mansard conversion. This particular type of extension and conversion are the premium and most expensive possibilities – but they will also dramatically expand the space within your loft room and maintain the style of your original home without compromise. These conversions can even be combined with a dormer window or dormer extension, usually to the rear of the property to comply with planning restrictions. This type of conversion will require planning permission and you will need to prepare for the roof to be removed, rebuilt, and replaced, all the while using a scaffolding structure to cover your house to protect it from the weather while the roof is off. Remember – this type of conversion can mean rebuilding around 30% of the property, the price of which will be discussed later.

loft conversion cost

How Much Can You Expect To Make?

If you approach your loft conversion in the right way and use the skills of trade professionals to do the job properly and thoroughly, you can expect to add around 20% of the value of the property with a loft conversion. You can roughly summarise this by saying 15% for the extra room and 5% for the extra bathroom space. When you consider the price of a property in and around the Greater London area this can result in a huge increase in property value. With that in mind, are you hungry to push ahead? Have you got a curious hunger kindling in your belly for that extra space, are you ready to go on that adventure and explore what you can achieve? Then read on – and let’s go on that journey together!

Loft Conversion – Planning Permission

This is always a daunting prospect, but it really needn’t be. It isn’t always required. For example, if you just wish to go for a loft conversion without constructing a new roof, it’s covered under permitted development. Furthermore, there are allowances you can follow to avoid applying for planning permission and the possibility of having your application denied. These are detailed below:

  • A volume allowance of 40 cubic metres of additional roof space for terraced houses
  • A volume allowance of 50 cubic metres additional roof space for detached and semi-detached houses.
  • No extension extends beyond the plane of the slope of the roof of the front of the property, facing the road.
  • No extension that will be higher than the current highest part of the roof.
  • No verandas, balconies, or raised platforms
  • Any side-facing windows must be obscure – glazed and 1.7m above the floor
  • Roof extensions are not permitted development in areas such as: national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas, and World Heritage Sites.
  • Roof extensions (not including hip to gable) to be set back a minimum of 20 cm from the original eaves
  • The extension cannot overhang the outer face of the wall of the original house.

Be aware that these permitted development regulations apply to houses, not apartments or other types of property. If you own a different property than a house, check out PlanningPortal.co.uk for more information specific to your circumstances.

As you can see from the above, there is plenty of scope for extending your home with a loft conversion without needing to apply to your local authority for planning permission. That said, even if you don’t need planning permission, it is worthwhile to check with the regulations of your specific authority, as it does vary depending on location and council. You would also be wise to discuss your planned loft conversion with an architect or a loft conversion specialist to discuss what you can and cannot achieve with the space that you have. If you want to do it, you should aim to do it right, pay the professionals who can get it done for you and you will reap the rewards at the end of the project.

For Your Consideration…

Building Regulations. This is the first part of the planning that you will need to consider and understand. Likely it will be covered by your designer or architect, but it is good to have an understanding of it beforehand.

Semi–detached or terraced houses … will need to comply with the Party Wall Act guidelines, which correspond to any shared boundary walls, or any walls which touch the boundary. The type of work that is included in this act covers a lot of what you will be required to achieve during the course of the conversion:

  • Converting a loft – cutting into boundary walls to support new beams
  • Underpinning
  • New damp-proof course
  • Increasing thickness
  • Demolishing and rebuilding the party wall
  • Extending above a story on the boundary side
  • Excavating work for new foundations – you must show you will not cause any damage to your neighbour’s foundations

If your project crosses off any of these boundaries – you must serve notice to your neighbours.

Serving the Party Wall notice…

If your project is covered by the Party Wall Act, you must send a letter to the owners of the neighbouring properties which will be affected and you must include the necessary information, such as :

  • Notice service date
  • Project start date
  • All names and addresses of parties involved
  • Work description

Without all of these, the notice will be invalid.

Present your notice with a copy of the Act and explanation, 2 months before starting. They will have 2 weeks to provide approval or rejection. They will get a template for both in the explanatory booklet you provide them with. If they do not respond, this will be deemed as a rejection.

Should this occur and you cannot agree on terms, you must employ a Party Wall surveyor, who will use their knowledge to mediate an agreement for both parties, resolving how the work can be carried out, how the work will proceed, the timing, how to prevent damage – and if damage occurs, how much will be owed to the neighbour.

Cost = £1000 – £2000 + VAT

Other regulations

You will have to make sure that your plans minimise heat loss through the floors, walls, and roof. You will need to make sure there is a 2m minimum of headroom in all escape routes, including the staircase. This can be reduced to 1.8m if there is a sloping roof, but the centre of the stairway must be 2m. There are electrical and fire safety regulations you must adhere to as well, so be aware of that when you are consulting your building team.

loft conversion design guide

Is My Loft Suitable For A Conversion?

Usually, the older the property the more suitable it is. This is because of the style of the roof in older buildings. The roofs tend to be steeper, with traditional frames and with higher ceiling joists. Anything lower than 2.2m from ridge timber to ceiling joist will require a rethinking of how to achieve the correct dimensions – possibly leading to the lowering of the floor or the raising of the roof.


One of the most important factors you need to consider for the comfort and practicality of your new loft conversion is the lighting. Natural or artificial?

Natural Lighting

This can be achieved through the cunning placement of new roof lights, openings made in the roof which are economic and allowed without planning permission. Or you can go for the dormer, which will extend out of the sloped roof, increasing the available and useable floor space as well as lighting the room. The mansard dormer will give you the greatest available space by lifting the roof out and housing windows in individual dormers.

Artificial Lighting

Here you can control the atmosphere within your new rooms. A carefully planned extension with lighting can really add value and quality of life. Ambient lighting, which acts as daylight, task lighting (ie reading lights), and accent/atmosphere lighting can all be incorporated here if you want to do it right.


Heating can be achieved through central heating or underfloor heating, and while you now have a larger space to heat within the house, it should make your house more insulated and therefore more efficient, if your construction has followed building regulatory guidelines.

The Extra Bathroom

This is where you can really add value to your property. By adding that extra en-suite bathroom or shower room, depending on space, you could be adding a further 5% to the value of the property, not to mention the practicality if you wish to stay in the property for the foreseeable future. We have a number of pages on our website which will guide you through how you can design your new bathroom and examples of projects we have already completed for you to take inspiration from, but what we must advise you here is to consider where the waste is going to go. Do you have a soil pipe from the drain to the vent above the property around the roofline? Or is there a soil pipe close by to which you can attach it to? Just consider because, while anything is possible, it is easier and cheaper when you plan around existing services.

You also need to carefully plan where you are going to place the appliances in the new bathroom. For example, you will need full headroom for a shower, but you can place a beautiful standalone tub under the sloping roof, under a roof light. You’ll most likely want standing space for the toilet and basin, but you’ll want to plan for the plumbing before you do the plastering, so you can conceal it in the stud walls and joists.

Health and Safety

If you’re in a house, you’ll need to consider the fire escape route. Generally, this will require a fireproof staircase leading from the loft to the final exit door, with a 30-minute safety time. Failing that, you can explore a sprinkler system.

How much does the loft conversion cost?

Well, we hear that question a lot. Our favourite answer tends to be, how long is a piece of string? Everything depends upon the specifics of your project and you don’t want to haggle for the price, because then you indirectly compromise on the quality of the finished project by limiting the manpower and subsequent time spent on delivering your finished project. What you need to consider is what project will meet your requirements and your budget. Will the cost of the project exceed the subsequent value of the property? Will the room serve the function and purpose that you will set out to achieve? Then you need to consider each component of the project, what is non-negotiable and what you need to pass on if it is exceeding your budget.

That being said, having done our research and the projects that we have been around, we have been able to present you with some ballpark figures for you to consider while you contemplate that big extension up. Use it as a guideline and reach out to the relevant people who can help you specifically.

  • Simple Loft Conversion – £30,000 +
  • Dormer Loft Conversion – £50,000 +
  • Hip to gable / Mansard – £75,000 +
  • Planning Permission – £206
  • Building Regulator – £600 +
  • Party Wall Surveryor – £1000 +
  • Architect / Designer – 10 – 15% of the budget

Of course, we say again, these fees will vary depending on the project, but take these points as a minimum and take your time to find experts who you trust and co-operate well with because then you will find the process pleasurable, exciting and the cost can be managed to your needs.

How long does the loft conversion take?

For this type of project, you will want to set aside anywhere from 9 to 14 weeks, depending on the type of conversion you opt for. You will want to aim for turnkey service, a company that will take over and manage the project for you from start to finish.

To Conclude

With all that in mind, what are your thoughts? Are you ready to take it on? It’s a big project but, with the right people around you, could be the best thing for you and your property. Don’t hesitate to get in touch with us, if you have any questions we can more than likely help you with our extensive construction experience or point you in the right direction of someone who has experience in the necessary field. And don’t forget, before you start, to notify your building insurer about the works, as most ordinary policies won’t cover house extensions or conversion building work!