Mansard Loft Conversion Cost

In this guide, we're going to explore everything you need to know about mansard loft conversion costs, the different types of loft conversions available and all the costs associated with these types of jobs.

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How Much Does a Mansard Loft Conversion Cost?

Mansard loft conversions are typically one of the more expensive loft conversion options compared to a dormer or hip-to-gable conversion.

Still, they provide the most floor area and interior design options. If you have a lot of mansard loft conversion ideas in terms of the design elements, mansard loft conversions are the best option for you to achieve your dream loft space.

As a result, building a Mansard extension can enhance your space while also increasing the value of your home. Here, we will go over all the information you need to know and the costs of having a mansard loft conversation!

The price of a mansard loft conversion is determined by various factors, not the least of which are the size and location of the property. In addition, the quality of the finish, as well as the fixtures and fittings, will impact the cost of a mansard loft conversion.

Most house types can accommodate this type of loft conversion, so a mansard roof loft conversion is an option if you have a terraced, semi-detached, or detached home. However, the design specification will vary depending on the property type, affecting the cost.

Because a mansard loft conversion includes changing the full sloping face of the roof to a close angle (at least 72 degrees), structural changes to the entire roof are required, so the larger your home, the higher the cost.

If you choose to install a bathroom, for example, you must pay for the cost of the suite as well as other elements in the finish, which can add thousands of pounds to the cost of the project.

A mansard loft conversion will cost between £45,000 and £55,000 but can cost up to £70,000 in London. Of course, the overall cost will be influenced by the quality of construction, fittings, and the complexity of the construction.

For example, if a bathroom is added, services for electricity and plumbing will need to be rerouted, and roof styles will vary, with some being more complex than others.

Each mansard addition will be unique, so determining an average cost is difficult, but loft conversions are not cheap. However, the additional living space they provide, particularly in congested cities like London, should not be underestimated, nor should the obvious value be added to the property.

Your house value increase may also be influenced by broader construction trends. Check out the latest construction statistics, which offers insights into these trends.

Mansard Loft Conversion Prices

In the table below, you'll find a comparison of how much different types of loft conversion cost in the UK for different-sized spaces.

As this table shows, hip-to-gable and dormer loft conversions cost significantly less than a mansard conversion.

For more information on different types of loft conversions, check out our loft conversion cost guide.

What Is the Cost of Mansard Loft Conversion Materials?

Do you want to save money on your loft conversion? You could think about buying the supplies yourself from a retailer. This section will cover the various supply costs for constructing a mansard loft conversion in your home.

Loft Flooring Prices

Flooring for your loft transformation is one of its most important costs. The cost of loft conversion flooring varies depending on the material used. Vinyl flooring, for example, costs about £6 to £14 per m², whereas laminate costs between £7 and £25 per m².

Hardwood is another popular loft conversion flooring option, ranging from £35 to £45 per m². If you want carpet for your loft conversion, you could perhaps budget between £5 and £30 per m².

Heating Prices

To ensure that your loft conversion is properly heated, you will need to install a new heating system. A standard horizontal or vertical radiator costs between £50 and £900, even as electrical radiators cost between £90 and £400.

Underfloor heating is more expensive, and it must be installed before your flooring can be installed. Wet underfloor heating typically costs between £60 and £80 per m². The floor is heated by pumping water through pipes.

The second alternative is dry underfloor heating, which typically costs between £30 and £40 per square metre. This includes electric mats and wires connected to the main power supply to heat the floor.

Loft Lighting Prices

Loft spaces can be extremely dark. This means that you must involve as much lighting as possible. For example, ceiling lights could be included. These start at £7 and can cost up to £4,000 if you want something more luxurious.

Lamps are another popular type of lighting. Table lamps typically cost between £3 and £1,000, while floor lamps cost between £12 and £1,800.

Smart lighting is one of the more advanced lighting options. These can be managed by a smart device and help you save money on energy while also lowering your carbon footprint. Smart lightbulbs range in price from £15 to £170.

Windows Prices

The price of loft conversion windows will differ depending on your style. If you are building a dormer loft conversion, you must consider the cost of dormer windows. Smaller dormers are normally priced at £150, while bigger dormers can cost at least £300 per window.

Roof lights are another common loft conversion window design. These are slightly more expensive, ranging from £320 to £550. However, they contribute to the creation of a modern and airy living space and greatly improve the aesthetic.

Additional Mansard Loft Conversion Costs

A mansard loft conversion is typically larger than other loft conversions, and it can add nearly an entirely new storey to the building.

As a result, you may want to make additional improvements to the rest of the property. This section will discuss the additional costs that may be incurred because of adding a mansard loft to your home.

Architect Cost

Not all contractors will require architect plans to complete a mansard loft conversion. However, making plans is still a good idea. It ensures that everyone stays on the same page throughout the project.

Architect fees are around £400 for a basic set of plans, but you can expect to pay up to £1,500 for more detailed plans that highlight the full scope of the work.

Given the project's cost, this is not a large sum, but it can significantly improve results. Another benefit of hiring an architect to create detailed plans is that it prevents you from making up your mind later, saving you money in the long run.

House Painting Cost

The cost of painting a house that's two-story and has three-bedroom house is around £850 in the UK. However, keep in mind that this is only an estimate, and many cost-variable factors will affect the final cost of your project.

These factors include the size of your home, its design, the materials used, and the tradesperson's daily or hourly rates.

For further information, please refer to our cost guide on painting the exterior of a house.

Roof Repair Cost

Because most loft conversions necessitate roof work, it gives you an excellent opportunity to clean up, repair, or replace your existing rook tiles.

As you'll already have scaffolding up, the roof repair costs you're quoted will tend to be lower than they otherwise would be.

For instance, roof cleaning costs around £450 — but, with scaffolding already in place, you'll be able to pay much less if you want to get your roof tiles pressure washed.

You might also want to schedule-in maintenance on your property's guttering system while the scaffolding is up:

New Boiler Cost

New boiler installation costs can vary depending on several factors. Boilers are typically replaced due to a fault, but they can also be replaced to improve energy efficiency.

For example, replacing your old boiler with a high-efficiency boiler with advanced heating controls could save up to £300 per year on your home's energy bills. The average cost of a new boiler, including installation, is £1,500 to £3,500.

Replacing a boiler is not a simple task, and it is certainly not a DIY project. In addition, gas boilers are subject to stringent safety regulations regarding replacement and maintenance.

Skip Hire Cost

Of course, a skip, or several skips, will be required when you're getting a loft conversion done.

The tradesperson or team that you hire to complete a loft conversion will likely have a skip hire company that they work with — and may have negotiated lower rates if you let them handle it.

The cost to hire a skip, if you wanted to handle it yourself, would be around £200 to £300 per week.

Keep in mind: A skip licence is required if the skip will be placed on the road instead of the driveway or in the garden. This licence must be renewed daily, and the local council determines the cost.

How Much Does Labour for a Mansard Conversion Cost?

Now, let's take a look at labour costs and timescales.

The labour cost of loft conversion is important because the job requires several tradesmen, each of whom will provide a different quote.

Here are the costs you should expect for each type of tradesman to help you get an idea of loft conversion labour costs.

Architect

The architect and structural engineer will create plans and structural calculations, the first labour cost on a mansard extension. These plans must be submitted to the local council's planning authority for processing, which takes at least eight weeks in most cases.

The fee for plan drawing and structural calculations and plan submission to the local authority will be in the region of £700 - £1,000.

Scaffolder Price

If you hire a loft conversion specialist, they will usually have a local scaffolding company that they work with regularly, and the cost of the scaffolding will be factored into your quote.

However, if you hire a scaffolding company on your own, you may pay more. The average weekly cost is between £750 and £1,100, depending on location and negotiation with the scaffolding company.

Carpenter Price

First and foremost, fixed carpenters will be the ones who detach the roof and build the loft, so they will be among the first trades on site.

An expert loft carpenter will earn around £130 and £170 per day, depending on where the property is in the country.

Electrician Price

Electricians will perform both a first and second fix on the mansard extension, and these works must be properly scheduled into the design to ensure that all necessary fittings are in the correct place before closing.

An electrician will charge between £150 and £280 per day, depending on where they work in the country.

Plumber Price

If a bathroom or kitchen is included in the mansard dormer design, a plumber will be needed for the first and second fix.

A plumber will typically charge between £150 and £270 per day.

Plasterer Price

Some loft conversion businesses will have a closing up team that will install insulation and plasterboard to the loft's timber frame. Other businesses divide this work between the first fix carpenters and plasterers.

If a closure team is used, each member will earn between £100 and £150 per day.

A plasterer will charge £130 and £170 per day, though this may vary depending on where you live in the UK.

How Long Does a Mansard Loft Conversion Take?

The amount of time spent constructing your loft conversion is important to consider because it will significantly impact the final cost. The longer the job takes, the higher the cost.

The size of your space will determine the length of time required.

A small mansard loft conversion will take between 8 and 9 weeks, a medium mansard loft conversion will take 9 and 10 weeks, and a larger mansard loft conversion will take 10 and 11 weeks.

What Impacts Mansard Loft Conversion Costs?

With a mansard loft conversion, there may be additional factors to consider. Numerous factors can raise the cost of a loft conversion above the average, ranging from the need for planning permission to the duration it will take to complete.

The size of the property and the quality of the finish are cost-influencing factors, but so are the need for more architectural involvement and the enhanced demand for services such as heating and hot water.

Finishing Quality

The materials used in the construction and fit-out of a mansard extension would significantly impact the cost. While some materials will be needed to meet specific Building Regulations standards, others will be a matter of preference or budget. Quite often, the option of roof covering is dictated in this manner.

While it may be necessary to adhere to either tiles or slate to maintain the consistency of a street, there is quality and thus price differences available. The price, quality, and durability of man-made slates versus natural slates, for example, will differ.

Location

The cost of a mansard dormer is also affected by the location of your property. For example, labour and material costs will be higher in London and the country's southeast, while prices elsewhere in the UK may be lower.

It may be necessary to commission a bat survey in rural areas because disturbing or disrupting bat habitats is prohibited. A bat survey can cost between £300 and £1,000, depending on whether it is preliminary or comprehensive.

Roof Tiles Type

Suppose the conversion entails replacing the roof, the type of tiles matters because some will almost certainly have to be changed as part of the construction. In addition, converting houses with slate tiles is typically more expensive than converting houses with concrete tiles.

Loft Conversion Dimensions

The higher the loft conversion cost, the larger the final space. A small and simple loft conversion can be completed for as little as £15,000 to £17,000.

A mid-sized loft conversion containing a double bedroom with two windows will cost £18,000 and £25,000. Expect to pay between £25,000 and £40,000 for a big double bedroom with an ensuite.

Interior Walls

If you decide to divide your new loft space into multiple rooms, the cost of the extra walls must be factored in. It will cost around £850 to install a stud wall and plater.

Plumbing Fees

The more plumbing you have, the more you'll have to pay. This is because there are material costs and the cost of a plumber's time. Plumbers typically charge between £35 and £45 per hour.

Electricity Prices

The more electrical outlets and lights you have, the more you'll have to pay. Electricians typically charge by the hour rather than by the job, so you can save money by selecting items that are simple to install. An electrician's hourly rate ranges from £50 to £120.

Planning Permission

With a few exceptions, most loft conversions do not require planning permission, but a mansard loft conversion most emphatically does. This is due to the extensive structural changes required to construct a mansard dormer.

A full new storey is added to a property, resulting in a complete change in appearance and being able to do more things on the foundations. The cost of applying for planning permission is slightly more than £200.

What's Involved in Building a Mansard Loft Conversion?

There are several stages involved in completing a mansard loft conversion; if you take on the project, you can expect to encounter all the following, as well as their associated costs.

Mansard Loft Conversion Plans

An architect, architectural technician, or surveyor will need to draw up plans for your mansard loft conversion. These plans should include all required structural changes.

Obtaining Planning Permission

Because of the scope of work involved in building a mansard loft conversion, planning permission is normally needed, even though this is not the case for most loft conversions, which are covered by permitted development rules.

You will need to contact your local authority's planning department to apply for permission to make the changes and have them authorised before you can begin work.

Week 1: Scaffolding and Opening the Roof

The scaffolding must be erected first. The job's materials will be collected on-site. This week, the roof will be opened.

Week 2: Structural Changes and Windows

This will happen next if the roof structure changes. If necessary, additional supports can be installed. For example, the windows for the roof light conversion will be installed now.

Week 3: Completing External Work

This week will see the completion of the external work. Any roof construction will be completed, and the tiles will be replaced and finished. Roof insulation will be installed as well.

Internally, the loft space will be prepared for any plumbing or electrical work required.

Week 4: Installing Floors and Walls

Any windows that have not yet been installed will be installed. The floor will be laid with any necessary ventilation. Plasterboard will be installed, as well as any internal walls.

Week 5: Completing Electricals and Interiors

At this point, the staircase will be installed.

If you have a bathroom installed, it can be done simultaneously. This week should also see the completion of the electrics.

The doors will be hung by the end of the week, the plaster will be skimmed, and the skirting will be installed.

Week 6: Wrapping Up

Any unfinished jobs will be completed this week if your contractor oversees the decorating that will take place this week. This week will also see the removal of the scaffolding.

Can I Build a Mansard Loft Conversion Myself?

Converting a loft is not a simple DIY project that can be completed in a few hours or on a whim over the weekend. Instead, it necessitates planning and deliberation.

Can you do it on your own?

Yes, if you have the necessary skills, you could do it yourself. However, many people prefer to hire a professional to handle the work because many things can go wrong. This could result in property damage.

It's important to note that this is a difficult task requiring extensive experience and an "I can do it myself" attitude. However, if you're ready to convert your loft, there are a few things you should think about before you start.

You will have to consider the following design issues:

• Your ceiling's height
• The kind of loft
• The services you want to put in place
• Problems with lighting
• Building a blueprint that suggests the strength of the floor and fire escapes if planning permission is required

Building Regulations & Planning Permission for a Mansard Loft Conversion

It's easy to become confused when it comes to an understanding the world of planning permission, especially when it comes to transforming your loft.

Whether or not you need planning permission for a loft conversion is determined by the type of work being done and the extent. We will go over everything in this section.

Building Regulations apply to all loft conversions, including mansard loft conversions. Building Regulations are the basic requirements for the design, construction, or alteration and must be followed for a project to be recognised as compliant.

Building control will inspect the construction at various stages to ensure that the correct Building Regulations are followed.

A mansard loft conversion entails raising the pitch of one side of your roof to almost vertical and flattening the top. A mansard loft conversion will almost always require planning permission. This is since it significantly alters the shape of the roof structure.

During your mansard loft conversion, a building inspection will visit the site at various stages to ensure that the conversion complies with Building Regulations, which will cost around £350 to £500 on average. This fee is usually included in the amount paid for the architect's plans to be submitted to the local authority's planning department.

While most loft conversions are permitted development rights, the significant changes to the loft space to combine a mansard extension require planning permission in most cases. In addition, the structure of the house, as well as the shape of the roof, will be altered.

The planning department of your local authority either grants or denies planning permission, whereas permitted development rights are given. The local council is concerned with preserving the area's character within its jurisdiction, which is why planning permission is a local rather than a national issue.

The effect on your neighbours is also considered whether your proposed development will impair their view or right to light. The appearance of your loft extension, or its design, will also be considered when applying for planning permission.

It is difficult to predict how long it will take to obtain planning permission for a mansard loft conversion, but there is a minimum consultation period of eight weeks. Just before this, the plans forwarded by you or your architect must be validated, and the time required for this can vary depending on a variety of factors.

If you have not provided all the required information, the validation of the plans will be delayed. The evaluation process can begin only after all the necessary information has been provided.

The first step is to publish information about your proposed mansard extension on the local authority's website for four weeks. This is done so that interested parties, like neighbours or utility companies, can view your plans or comment, accept, or object to them.

A planning officer then evaluates your proposed plans and considers any comments or objections raised during the public accessibility stage.

The planning officer will also assess how well your proposed loft conversion will blend in with its surroundings. Finally, on or around the eight-week mark, whether to approve or deny the application should be made.

Applying for planning permission in the UK is around £200, with some variations between England, Wales, and Scotland, but these are only a few pounds.

Your local authority's planning department can provide you with information on planning permission. Although general information is available on council websites, it is preferable to speak with someone for more specific information.

Types of Mansard Loft Conversions

A Mansard conversion is typically built at the back of your property and has a horizontal roof with a nearly vertical 72-degree back wall. This creates a large amount of loft space and ensures that the proportions of the room are desirable.

Windows in a Mansard are typically housed in a box-shaped Dormer that slightly projects internal space and allows natural sunlight to flood in.

Furthermore, because the windows are vertically oriented outwards, the Mansard loft conversion appears to have always been a part of your home. This section will discuss the various types of mansard loft conversions and their benefits and drawbacks.

L-Shaped Mansard Loft Conversion

An L-shaped mansard loft conversion is when two structures are built in such a way that they connect. Typically, one is built on the rear outrigger roof and the other on the main roof, giving it the instantly recognisable L-shape.

Because of the shape, L-shaped mansard loft conversions are only suitable for certain properties, primarily Edwardian or Victorian properties with an existing addition at the back known as a two-storey outrigger. This construction style is a great way to get more space out of a property, especially if you own a mid-terrace property.

Pros

✔ Great way to add space

✔ Blends into a home

Cons

✖ Not suitable for every home

Double Mansard Loft Conversion

A double Mansard loft conversion is also available, similar to the standard Mansard conversion. The distinction is that it includes a Mansard on the front side of the property. This sort of loft conversion is prohibited in some jurisdictions.

The double Mansard loft conversion is like a regular Mansard loft conversion, but it includes a Mansard towards the front of the property. These loft conversions are subject to planning restrictions in some parts of the country.

Pros

✔ Popular choice

✔ Adds value to a home

Cons

✖ Need planning permission

Hiring Contractors to Build a Mansard Loft Conversion Checklist

The significance of bringing on the right builder cannot be overstated. It will result in the highest quality build, but having a good partnership with your builder will make sure you get exactly what you want while possibly saving you time and money.

But where do you find such a builder? Use our checklist to find the best contractor for your loft conversion.

• Locate a builder in your area — Finding a local builder can be extremely beneficial when it comes to your construction. Time on site, knowledge of local planning permission, builders' merchants, and other local trades are invaluable nuggets of information that you'll appreciate on-site. In addition, there's no harm in going for a walk around your neighbourhood or taking a short drive around the neighbourhood to see if any construction projects are going on. It will give you an idea of the builders who are active in your area, and if you see a builder's board, it is a sign that, at the very least, this is a builder who is proud of their work and looking for more.
• Get recommendations — Many trades rely on word of mouth, and if you can find a builder through someone you trust, whose work you can go see, you can decide whether they'll do a good job.
• Speak with previous customers — Don't be afraid to ask for a list of previous customers; if they're confident they've done a good job, they should be happy to provide details. This will provide you with an excellent opportunity to learn more about them and see examples of their work first-hand. Meeting previous customers is a great way to learn about the quality of a builder's work and other important factors.

FAQs

Sources

https://www.planningportal.co.uk/permission/common-projects/loft-conversion/planning-permission
https://www.cncbuildingcontrol.gov.uk/wp-content/uploads/2023/06/CNCD-051-Loft-Conversion-Easy-Guide.pdf
https://www.simplyeasyrefurbs.co.uk/mansard-loft-conversions-an-ultimate-guide/
https://loftconversions.wales/diy-loft-conversion-guide/
https://cityloftslondon.com/mansard-vs-dormer-loft-conversion-all-you-need-to-know/