How to cut the cost of your loft conversion

Any home renovation project needs a budget. Some budgets are not really budgets, but most of us set aside a specific amount of funds for a loft conversion or a basement conversion or a home extension.  

This article in Houzz, recommends a variety of ways you can cut and control the cost of your loft conversion. 


If you are considering an loft conversion, an extension, or an overall property refurb give us a call on 02081917595. Or better still, book a FREE consultation with us and we’ll visit your property, discuss your ideas and share some of our recommendations with no obligation. 

Loft Conversion in London – What costs do I need to consider?

Loft conversions are one of the most cost-effective ways to increase the space in your home. In London, in particular, where space is at a premium, basement and loft conversions are a common feature.

Whilst excavating a basement is a more costly affair, a loft conversion is a relatively more ‘value for money’ kind of project. Of course, you can go to town with how much you spend on your internal specs, but if you had to choose a way to increase your living space in a way that won’t break the bank, a loft conversion is probably your best bet.

Loft conversion costs depend mainly on two factors:

  • The size of the project
  • Where you live

Though loft conversions generally increase the value of a property, how much any potential increase could be is governed by where you are in the country. Space is hugely expensive in the South so a loft conversion there would add more value to a property than it would in the North. Loft conversions can cost between £20,000 at the bottom end and £40,000+ at the top end. A conversion in a small house in rural England may cost £16,000, while the same job would cost a London resident upwards of £30,000.

Before considering a loft conversion, make sure your home will meet the current eligibility criteria, so you don’t find yourself building illegally. As long as your loft has a height of 2.4m+ (approx. 8ft), it’s eligible for conversion.

Loft extension or conversion prices also vary according to the type of loft conversion project you are undertaking.

  • Room in Roof Loft Conversion

This is one of the simplest kinds of loft conversions and prices start at around £15,000. The primary costs associated with this kind of conversion are a staircase, insulation, fire safety considerations, skylights, electrics, heating and lighting.

  • Hip to Gable Loft Conversions

This involves converting the hip (sloped) side of the roof into a flat edge which provides added space inside the loft. The hip-to-gable loft conversion price will also vary depending on what else you have done to the loft.

Average prices range between £30,000-£35,000.



  • Dormer Loft Extension

Dormer loft conversions extend outwards from the back or side of the roof in a box shape. These are sometimes referred to as kennel or box conversions and provide added space in the loft room. Dormer loft conversion prices vary depending on how many dormers you add and what else you do to the loft, but on average, they range between £19,000-£30,000.

  • Roof Structure Alterations

If you decide you want to completely overhaul the roof of your existing property and create living space at the top of the house, you will need planning permission. This is the most expensive of all kinds of loft conversions and prices are likely to start at around £40,000 as they will require the removal and rebuilding of the entire roof. This may be necessary either because the existing roof is not an appropriate shape, or because it is not structurally sound to undergo any of the simpler extensions.

You will also need to consider the costs of adding natural light into the space in the form of skylights, dormer windows and rooflights.

Rooflights that follow the pitch line of the roof are the most economical and can be done without planning permission. It is fitted by removing the tiles and battens where the rooflight will be fitted. The rafters are cut to make way for the rooflight after suitably reinforcing the remaining rafters. The rooflight frame is then fitted and flashings added before making good the surrounding tiling.

We found this handy cost guide that might give you a region-by-region idea of the average cost of a loft conversion.

At SDA Build London, we offer a complete design and build service, project managing your conversion or extension from start to finish. If you are considering converting your loft, give us a call on 0208 191 7595 or email us at for a no-obligation quote. We are specialists in all kinds of building work, especially in London, and we’ll be happy to share our recommendations with you.

9 Extension mistakes to avoid

extension mistakes to avoid

Building an extension to your home, whether it’s a single or double storey or a loft conversion, can be very exciting. It’s important to have done all your research and have all your ‘ducks in a row’ before you bring the diggers in to avoid making mistakes that can make you wish you had never embarked on the project.

This article in Homebuilding & Renovating outlines 9 possible blunders you must avoid to ensure the smooth running of your extension project.

If you are considering an extension, loft conversion or an overall property refurb give us a call on 02081917595. Or better still, book a FREE consultation with us and we’ll visit your property, discuss your ideas and share some of our recommendations with no obligation…

Loft Conversions in London – All you need to know

loft conversion

Loft conversions in London are fast becoming the preferred way to increase living space in a home. Most homes across London particularly in Central London don’t have the ability to extend out or on the side. With prohibitive stamp duty rates and the hassle of moving home, converting the loft is one of the most cost-effective ways to create more space in a home.

If you are at the ‘thinking’ stages of whether to embark on a loft conversion project, perhaps these considerations might help you decide. And if you do decide to go ahead, do give us a call on 0208 191 7595. We provide a complete design and build service and would be happy to provide you with a free quote.

Let’s get started…

Planning Permission – Do you need it?
Sometimes you do and sometimes you don’t. In most cases, loft conversions tend to be considered Permitted Development (PD), but only if your design adheres to criteria as specified by the planning department.

If you plan on extending beyond the limits and conditions of PD, or your property is listed or located in a conversation area, then you will need to apply for planning permission. You will also need planning permission if you are altering the roof height or shape.

Rooflights and dormer can be installed under PD, but they must not sit forward of the roof plane on the principal elevation, nor must they be higher than the highest part of the existing roof.

Building Regulations
You will definitely need building regulation approvals and certification. A building control surveyor will inspect your conversion at various stages and will be responsible for issuing a completion certificate upon final inspection. You can appoint a building regulation inspector through your council or appoint a private building regs company. We suggest you budget between £1000-£2000 for building regs. You can find out more about building regulations on your council website or on the Homebuilding & Renovating website.

Party Wall Agreements
If yours is a terraced or semi-detached property you will need a party wall agreement with your neighbours. A terraced or semi-detached house or flat, is likely to have a shared wall with a neighbouring property. The Party Wall Act prevents building work undertaken by one neighbour undermining the structural integrity of shared walls or neighbouring properties. It is also designed to avert and resolve potential disputes with neighbours. If your property is detached, a party wall agreement is usually not necessary for a loft conversion.

Is my ceiling suitable?
Loft conversions are not possible in all homes. Whether your loft is suitable for conversion depends on a number of factors including, available head height, pitch of the roof, structure of the roof and any obstacles.

According to Homebuilding and Renovating, when you measure from the bottom of the ridge timber to the top of the ceiling joist, you need to have at least 2.2m of usable space for a conversion to be suitable. While the Building Regs impose no minimum ceiling height for habitable rooms, you will need to factor in the 2m headroom required for stairs (although you could relax this to 1.8m on the edge of the stair if needs be).

Also, the higher the angle of the roof pitch, the higher the central head height is likely to be, and if dormers are used or the roof is redesigned, the floor area, and potential for comfortable headroom, can be increased.

It’s important to appoint an experienced architect (our Architect Guide has a list of accomplished architects you can choose from) and structural engineer to design loft conversion. These professionals should be able to determine exactly what structural support your loft conversion needs and find solutions to any obstacles that might arise. There is always a solution to a structural conundrum; it just may not be a simple solution.

Depending on the specs you choose, the cost of your loft conversion can be as high or low as you want. Typically prices start at around £15,000 for a room in the roof loft conversion, which is the cheapest and most straight forward option.

This will usually involve the reinforcement of the floor, skylights, insulation, a staircase to the loft, electrics, lighting and heating and fire safety measures such as fire doors and smoke alarms.

There are several factors that will affect how much it will cost to convert your loft including the roof structure, existing available space, whether you need alterations in order to accommodate the staircase. If you add dormer windows you will be able to increase the space, but this could cost upwards of £20,000.

The average dormer loft conversion with a double bedroom and en suite costs about £35,000–£45,000.

If you decide you want to increase the roof height or change the overall structure by removing the existing roof and redesigning the overall look and structure, the cost will increase significantly and start at around £45,000.

Fire Safety
For us, safety is one of the most important considerations when we project manage a loft conversion or extension.

If it’s a single storey loft conversion, you will need to make sure that the new windows are large enough and low enough to escape from. Egress window openings are needed to serve all first-floor habitable rooms, but not bathroom and openings should be at least 450mm x 450mm and at least 0.33m2 in area.

If your loft conversion transforms a two-storey house into a three-storey home, escape windows that are over 4.5m from ground level are not viable. Instead, the Building Regs require a protected stair enclosure that leads right down to the final exterior door.

The new floor joists of your loft conversion will need to offer at least 30 minutes’ worth of fire protection, which could mean replastering the ceilings in those first-floor rooms below.

The loft room will also have to be separated by a fire door, either at the top or bottom of the new stairs. The existing doors on the stairway to both ground and first floor should be able to provide 20 minutes of fire resistance or be replaced. They can’t be glazed either (unless with fire-rated glass), so you may want to consider windows or rooflights to bring daylight to the stairwell.

There are plenty of permutations and combinations and factors when it comes to converting your loft. The bottom line is that you want a loft conversion company or a team who will provide you with a start to finish service to the highest standard. At SDA Build London we can offer you a complete service from design to build and managing the entire project. We have a team of highly experienced architects, structural engineers and project managers who will work with you to solve any problems and give you your dream home.

Give us a call on 0208 191 7595 or email us at to discuss how we can help.

To have a look at the kind of work we have done, why not download our free brochure? And if you need any help with managing your building project, our free project management checklist has been hugely popular.

Basement Excavations and Conversions in Chelsea and Westminster

high end basement bar chelsea

If you live in the Chelsea & Kensington area, then you know that it’s all about basements. You’ve probably seen your friends and neighbours, like Jemima Khan and Andrew Lloyd undertake home renovation projects with basements excavations and conversions.

In fact, according to an article in the Telegraph, a few years ago, developer Alan Waxman built a house not too far from Chelsea- in Notting Hill, that has two basement levels. The back garden has been lowered so that it stands at upper basement level through and open plan kitchen. In the lower basement he’s built a gym and bedroom.

Another trend is the “Garden Basement”. Literary Agent, Ali Gunn has a 33 foot subterranean reception room under the entire length of her garden.

According to an article in The Independent, there were 4650 planning permissions granted between 2008 and 2017 in the upmarket central London areas. Of this, over 1000 were in the Royal Borough of Kensington and Chelsea.

Quoting from the article, “It is the 785 large and 112 mega-basements that should be the real focus of our interest. These almost 900 excavations are on a different scale to the standard constructions. Together they contain: 367 swimming pools, 358 gyms, 178 cinemas and 63 staff spaces. We also found 14 car lifts, seven art galleries, two gun stores – and one owner who admitted to building a “panic” room…

Perhaps the most “luxified” development we discovered was one that had been granted planning permission in Holland Park in 2013 under a large semi-detached house. It consisted of a new three-storey basement under the entire property and part of the rear garden.

It includes a staff kitchen, staff bedroom, six WCs, a gym, a media room, a family room, a family kitchen, a guest bedroom, a guest kitchen, a laundry room, a drying room, a sauna, a steam room, two shower rooms, a jacuzzi, a plunge pool, a pantry, a full-sized swimming pool and a beach. Yes, a beach.”

In fact, if you have about thirty minutes, watch this BBC documentary on Millionaire Basement Wars in London to enter a world where the words luxury, lavish and splendour are understatements. It’s truly an eye-opening documentary so be sure to watch it, if you are a property or home renovation enthusiast.

One of the perks of building a basement in areas like Chelsea and Kensington is the value-add to the property, as you will see in the video. According to Savills, in an article in the Telegraph, on a standard 4 bedroom period home basement conversion, the value of the property can increase by over 15%.

Not everyone in Chelsea and Kensington however are happy with this basement boom. With the surge in construction, the disruption to neighbours and the neighbourhood, this council receives the maximum complaints from residents with regards to these basement conversion projects. As a result, the Royal Borough of Kensington and Chelsea have tightened regulations on building basements so that now you can go down only one level and your basement cannot take up more than 50% of the garden space.

With the number of basements being built in Chelsea and Kensington on the up, we have done most of our basement projects in these areas and are well-versed with council planning permission and building control requirements. Not only that, we know what clients in these areas are looking for; state-of-the-art equipment and controls, every aspect bespoke and unique to them and a space that will be the envy of all who visit.

Give us a call on 0208 191 7595 or email us at with your requirements and we’ll be in touch. If you want to get a feel of the high standard of work we’ve done, in some of London’s most prestigious areas, why not download our brochure? We’re sure you will appreciate the high-specs we are used to providing our customers.