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Dormer Bungalow extension costs and prices

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Dormer Bungalow extension costs and prices

Bungalows are single-storey homes, and converting the attic space into a new room - usually with a dormer window to add height - is known as a dormer bungalow. The typical dormer bungalow conversion costs around £15,000-£20,000, with more complex builds costing £45,000 and upwards.

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What is a dormer bungalow extension?

Crating a dormer extension can almost double the living space inside a bungalow, and add significantly to the value of the property.

Box dormers are an option to build into the existing roof space. This option adds ceiling height and makes an attic a more usable space, mainly if the pitch of the roof is steep.

Most dormer conversions are used to create an upper level, usually for an additional bedroom or bedrooms, although can also be used to create a double-height vaulted interior ceiling.

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What are the benefits of converting my bungalow to add a dormer window?

The advantage of this type of conversion is that it utilises often-empty attic space and turns it into a habitable part of your home.

You can use this space in several ways:

  • Adding additional bedrooms
  • Creating more living space
  • Installing an extra, or larger, bathroom
  • Freeing up room downstairs to have a more flexible layout

Dormers add value to your home, bring in more natural light, and are an efficient way of adding value without the cost of building an extension alongside your existing home.

How long does it take to build a dormer bungalow conversion?

The exact timescale for your conversion will depend on the ease of access and how complicated the design is. Most dormer extensions can be completed within as little as 6-8 weeks.

Bear in mind that the design and planning process can take longer than the build time itself. If you need a Party Wall Agreement, this can take upwards of six months alone, so it is always wise to plan for around 6-12 months total project time.

How much does a bungalow dormer extension cost?

The cost of your bungalow extension will depend on lots of factors:

  • How large your bungalow is, and therefore how large the extension will be.
  • How many box dormers or dormers windows you would like to install.
  • What utilities and fittings you need for your new living space.
  • What materials and design you choose.

On average, a bungalow attic conversion costs between £15,000-£20,000.

What options are there for my bungalow dormer conversion?

There are lots of options when it comes to designing your attic conversion. Which is most suitable for your property will depend on your budget, what you would like to use the space for, and the design you would like to choose.

Dormer conversions are simply an extension to your roof. You can extend upwards from a sloping roof, and the finish can be either flat or pitched.

Another reason homeowners opt for a dormer extension is that they are often able to build without planning permission, depending on the size and scope of the conversion. Not needing planning permission makes the process faster and cheaper.

Read more information on the cost of adding a second floor to a bungalow here. 

Where on my property can I build my dormer bungalow extension?

Many dormer attic conversions are positioned at the back of the property. Choosing to extend to the rear of your home often means less likelihood that you will need planning permission, and does not impact the curb appeal of your bungalow.

However, you can also build a dormer extension to the front of your home, mainly if the extension is relatively small, or if this is the best aspect of your bungalow to attract natural light.

The build stages of a dormer bungalow extension

When planning an extension, it is wise to think about each stage beforehand to gain a realistic idea as to how long the total project will take.

Stage 1 - Planning and budgeting
You might have a firm idea as to how your dormer extension should look or may need to look around for inspiration. It is best to commission a professional to help with the designs, such as an architect or surveyor.

Some bungalows have plenty of space to expand into the attic space but are constructed with walls that are not suitable for bearing heavy loads. In this case, you may need to plan for reinforcements before the build can take place.

Stage 2 - Planning permission
While lots of bungalow extensions will not require planning permission, it is best to check this beforehand. If you can build under the criteria of permitted development, you will still need to consider notifying building control to ensure that your extension receives a formal verification certificate.

Stage 3 - Building regulations
Building regs are not the same as planning permission and are a form of certification provided through your local authority that proves that your extension has been built to the correct standards.

Usually, you will need to submit plans, or advance notice, to your local authority. They will then approve the plans, or arrange for an inspector to visit during the build to confirm that the works comply with regulations.

It is also worth thinking about Party Wall Agreements, which might apply if your bungalow is semi-detached. This means having an agreement with your neighbours to confirm that they do not object to the work taking place.

Stage 4 - Extension work
While you will have already drawn up an idea of the budget when working on the designs, it is worth revisiting these once you have the go-ahead to begin your build. It is very easy for costs to spiral out of control!

In most dormer bungalow extensions, scaffolding is erected, and the floor strengthened as the first stage of works. Then the roof is altered, the internal walls fitted, and the structure is insulated.

Once this is complete, the internal work begins with utilities installed, flooring laid and fittings constructed.

What are the professional costs involved with a bungalow dormer extension?

The built itself will make up the majority of the budget, but it is also essential to be aware of the professional costs involved.

These include:

  • Professional design fees - around £1,000.
  • Planning permission - £206 for a home extension (this can be higher if revisions are required to your plans).
  • Building regulations - the fee for building control approval will depend on your local authority, and is usually set against the value of the building work - this is typically around £400 - £800.
  • Party Wall Agreements - many such agreements need a Party Wall Surveyor to draw up a formal agreement. This process can be extremely complex if your neighbours disagree with the build, so it is crucial to let them know in advance and address any concerns.

How is a dormer bungalow extension built?

The materials and fittings you choose for your bungalow conversion will make a big difference to your budget. If you are extending to create an extra bedroom, the project will be relatively simple.

Adding in a new bathroom can add significantly to your budget since you will need to factor in the cost of the suite, plumbing works and fitting.
Build stage 1 - your contractor will first work out the best way to access the site. For most bungalows, this involved using scaffolding and sometimes putting up a roof cover to ensure that any bad weather does not cause delays.

Build stage 2 - your roof will not have been designed to bear heavy loads, so initially, the access point is created, and the floor strengthened before work can begin.

Build stage 3 - Once access is available, your new roofing will be erected. When this is complete, and the structure is watertight, the new internal walls can be established and the walls insulated.

Usually, the glazing will be installed at this stage, although sometimes it is more efficient to weather proof the frames and install the glazing later.

Build stage 4 - Usually, at this stage, the staircase is installed. This is where your extension begins to take shape.

However, usually, the scaffolding will be left in situ - this minimises disruption, contains dust and debris away from your living space, and allows continual ease of access.

Build stage 5 - Now the internal fittings can begin; usually split into a first fix and second fix. The first will involve things like the electricity and plumbing points, followed by plastering and any joinery work.

After this is finished, more aesthetic finishes are completed, such as installing electrical sockets, installing any fittings such as bathrooms, and decorating work.

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Frequently asked questions

What other build costs are involved in a dormer bungalow extension?

There are a few things to think about when planning your bungalow extension.

  1. Are there water tanks in your loft that will need to be moved?
  2. Will work be required to alter your home plumbing system?
  3. What sort of roof do you have? Concrete tiles are usually cheaper than slate, but this will often depend on the existing materials.
  4. Was your bungalow built with a roof frame or wooden trusses? Many homes built before the 1960's will have been constructed with a frame. Trusses are faster and easier to make but can bear less weight, so many require reinforcing.

How can I keep the costs of my dormer bungalow extension down?

The first way to control your budget is to work with competent tradespeople. You should always look to obtain three quotations but also ask for examples of similar previous projects.

Recommendations and a portfolio are a great way to take a look at your contractors' previous work and to move forward with the assurances that their conversions are to a good standard.

You can either work with a contractor or an architect to manage the project from start to finish or choose to hire individual tradespeople for each stage of the build.

Another option is to work with a dedicated dormer conversion company, who will provide the tradespeople without your needing to carry out any additional work. This is often the most convenient option and means that you don't run the risk of leaving out any essential costs from your budget.

Is a bungalow with a dormer conversion still considered a bungalow?

Usually - yes! It's an interesting question since some planners refer to extended bungalows as 'one-and-a-half' homes.

This style is becoming increasingly popular; bungalows remain in high demand due to a limited number of properties, and since this style of home is easy to maintain, has a compact layout, and avoids using stairs for homeowners who find this problematic.

However, a dormer extension can be used to create additional guest accommodation without detracting from the original ground floor layout. It is also often used to increase overall capacity, enabling the homeowner to change their original design to create a more spacious ground floor.

A dormer bungalow falls into the classification of a 'one-and-a-half' home but remains a bungalow for other intents and purposes.

Are there any downsides to building a dormer bungalow extension?

Most homes have a pitched roof, with sloped ceilings on their top floors. This means that the wall height tends to be restricted, and you should think about the headroom in your dormer extension plans to ensure that there is sufficient space.

You will need to plan for the staircase, and where on your ground floor this will be positioned. This does take up space in your original bungalow layout but is offset by the additional space created in your attic.

The upper level in a dormer bungalow extension will, of course, be smaller than the ground floor, and therefore is not as well balanced as a double-story home. However, putting some thought into the design and how you use your space can make this a valuable and cost-effective way to maximise the saleable price, and usability, of your bungalow property.

What other types of attic conversion could I choose?

As well as a dormer extension, you could consider a mansard conversion or a hip to gable roof extension.

Mansard conversions are usually built to the back of your property and have a flat roof made onto a back wall that slopes inwards. The slope includes windows, and while this is a more complex build than a dormer extension, it does create a lot of living space.

Hip to gable conversions alter the sloped roof to create a vertical gable end and an elevated extension on top of your original roofline that creates significant extra space.

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