Quality Over Prices

Dominator INSULATED Garden Office

Approx. W5.5m x D3.5m / W18' x D11'6"

(Sizes shown are approximate & full sizes are shown in the product specification)

From £7,229.99 £7,649.99
Save £420
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  • 75mm walls, highly insulated for year round use
  • Customise to a configuration that works for you
  • 24mm double glazing. NOT thinner 14mm glazing
  • Highly insulative SuperFOIL for year round comfort

Dominator INSULATED Garden Office Overview

Introducing our Dominator Garden Office, designed and crafted to enhance any chosen space, adding the option for more room for a home office, lounge area, or a mix between the two. This garden office offers endless oppertunities, as well as the potential to add value to your property. Our innovative DIY panel system ensures a seamless and stress-free construction process, allowing you to bring your vision to life effortlessly.


The Dominator is also fully insulated, meaning you’ll be able to use the space all year round. With the walls, roofing and flooring, all delivered to you in easily manageable panels, each equipped with pre-installed insulation. So you can enjoy your garden office throughout the year, keeping warm in the winter and cool in the summer!

Key Features

  • High internal eaves height - 2.09m (6' 10")
  • Secure, industry leading multi-point locking systems
  • Designed with the DIYer in mind for quicker install
  • Superfelt included as standard
  • Vents supplied for airflow and to minimise moisture
  • 10 Year guarantee on pressure treated floor bearers
  • All fixings included at no extra cost
  • Secure, Industry leading 10-point locking system
  • Sturdy 19mm tongue and groove roof and floor

Additional Information

Established in 1994, we are Industry experts that YOU CAN TRUST!

We are a UK family-run business supporting more than 700 jobs up and down the UK with dedicated distribution centres strategically placed across the country so that we can deliver products to you quickly.

We have been selling garden buildings and structures for decades, so you can realise your dreams and create the perfect outdoor space, whether it is for relaxation, a place of work or a destination to fulfil your hobbies or to simply entertain…

…our vast range of products means that you are bound to find the ideal solution for YOU.


Why have so many chosen to buy from Dunster House?


Trusted by Tens of Thousands of Customers

Our customers are at the forefront of every decision that we make, that is why we have been able to sell millions of products to satisfied customers up and down the county. Why not check out our Trustpilot reviews? They speak for themselves!


Buy Direct from The Manufacture!

Buy directly from Dunster House, and you will benefit from great value prices. Who wants to pay more than you have to? Well, at Dunster House you can cut out the middleman – We design, We make, We deliver!


Exceptional Value, Superb Quality

We are known for providing exceptionally high-quality products at affordable prices. Be wary of competitors who offer lower-spec products, cut corners to save on prices and try to upsell you on necessary items such as flooring, roofing material and safety features!

To ensure the very best quality, we only use slow-grown White Spruce Timber, which is harvested in cold climates to ensure solid, dense log rings. This gives the wood superior strength and longevity, and a much more consistent colour than the likes of Pine.


Products Designed for the DIY Market

All of our garden buildings are designed with the DIY market in mind. Why? Because it saves the need to employ a carpenter or builder helping you to save money and costs. Follow our detailed instructions and you will be showing off your achievements to friends and family in no time.


Speak with Experts and Buy with Confidence

Our in-house sales team are available during business hours to answer any questions you might have before making a purchase. With expert product knowledge, have your questions answered so that you can buy with confidence.  Contact us today


A Wide Range of Products to Choose From

Explore our extensive range of products online or download one of our free brochures for more detailed information. Our user-friendly website allows you to easily search and filter through our garden buildings to find exactly what you need. Each product page provides comprehensive descriptions, high-quality images, and customer reviews to help you make informed decisions.

If you prefer a more traditional approach, our free brochures are available for download. These brochures provide in-depth insights and product specifications to help you get the most out of our products. Whether you’re browsing on-the-go or reviewing options at your leisure, our brochures are designed to be a convenient and informative resource.

The majority of our garden buildings, structures and climbing frames are made from natural materials therefore variations in the materials provided can occur along with natural changes and differences. In some cases too, it may be necessary to treat your product. Be an informed buyer and learn more.


Looking for some Inspiration?


Explore our customer inspiration gallery, a treasure trove of creativity and innovation, showcasing a myriad of garden ideas brought to life by our valued customers. Immerse yourself in a visual journey where elegant outdoor living spaces come together to inspire your own garden projects.

Dive deeper into our customer case studies, where compelling customer stories unfold alongside captivating images. These real-life examples illustrate how our products have been used to achieve stunning results, offering practical inspiration and guidance for your own endeavours.

Whether you’re envisioning a serene sanctuary, a productive work space, or a stylish entertainment area, our customer inspiration gallery and Case Studies provide a wealth of ideas and solutions to help you realise your garden dreams. Let these stories and images ignite your imagination and empower you to create a garden space that reflects your unique style and aspirations.

There is nothing more annoying than being in the middle of building something and finding that you don’t have the right fixings to continue. We include all of the screws, nails and fixings that you will need to put your garden building together – not many of our competitors are that thoughtful. This eliminates the need to worry about the type of screws or the length of nails you might need to get started – it’ll all be with your delivery.

Fixings Included

Wish to customise your Garden room? As the wall panels supplied are of the same size, this means that a wall panel can be replaced by a window panel (for instance) and the wall panel used elsewhere, the doorway (2 panels) can be changed with any mix of 2 panels.

You could put the door on a side aspect and have a wall of windows to the front aspect if that is how you want your Dominator to look.

Customise the Dominator to a configuration that works for you!

Dominator Configuration DIY

A low U-Value means that your walls, roof and floor radiate less heat, in reality, you keep cool in the summer and warm in the winter whilst having lower energy costs. The Dominator has low U-Value walls, roof and floor thus keeping your running costs down. The walls have a U-Value of 0.63, roof U-Value is 0.49 and the floor U-Value is 0.64.

The lower the U-Value the better! Be weary of any competitor products on the market that don’t advertise U-Values.

Fully Insulated Dominator

All of our garden buildings have pressure-treated floor bearers as standard. This treatment prevents the timber bearers from rotting for up to 10 years and causing your garden building to sink. Pressure treatment forces the wood preservative into the timber rather than simply dip treating (essentially just covering the exterior) like many companies still do. Who wants to have to annually deconstruct and re-treat the bearers each year!

Due to this costly but effective process, we can offer our customers a genuine 10-year guarantee against rot and insect infestation on the bearers.  We do however recommend applying a good quality water repellent to the timber to prolong the longevity of the timber. Shockingly many of our competitors still offer untreated bearers to keep their costs down, so beware!

All our Pressure Treated timber is for Use Class 3

Pressure Treated Bearers

Rotten Untreated Floor Bearers

Lightweight and flexible. SuperFOIL is ideal for use in Garden rooms like the Dominator. It is preinstalled in the roof and wall panels and is just unrolled across the ground bearers for floor insulation. As it comes on a roll the floor installation is quick and very easily installed.


If you had any doubts as to the quality of the insulation, don’t!  Firstly, it’s made from 40% recycled material, so it’s great for the environment, but not only that it’s of a high enough standard that it can be used in homes as part of roof, walls and floor insulation.


When comparing competitor products, be sure to check what insulation is used. Some competitors may use cheap materials such as bubble wrap which is nowhere near as effective!

Garden office insulation

The bearers of your garden building are pressure treated to help protect your garden building from the ground up. We provide a 10 year guarantee against rot and insect infestation for all pressure treated timbers.

Unlike some competition, we can offer a genuine 10-year guarantee against wood-eating fungal and insect infestation on pressure-treated timber.

All our Pressure Treated timber is for Use Class 3

10 Year Guarantee on Pressure Treated Timber

Purlins are the large timbers used for structural support in buildings. We use very thick, heavy duty roof purlins to support your garden building.  At 140mm x 45mm they are amongst the thickest purlins available on the UK market. Competitors will often use thinner purlins to keep their costs down which means their roofs will not be as strong as ours. Using thinner purlins risks the roof collapsing or sagging during extreme weather – and that’s the last thing anyone wants!

Heavy Duty Roof Purlins

This garden building is under 2.5m high. Why does this matter? Under permitted development rights, buildings under 2.5m high can be placed as close as you want to a boundary (eg. a fence line) without planning permission. Garden buildings that are over 2.5m high need to be placed over 2m away from any boundary (eg. a fence line), which could lead to a lot of wasted space. If you want to find out more about permitted development rights see our planning guide

Both our doors and windows are fitted with internal beading used to secure the glazing in place. This beading style is typically found in uPVC windows and is a proven method of security. However, there are still some companies that externally bead their windows. Allowing intruders to remove the glazing from the outside of your garden house and gain access.

internally beaded windows

Security is important for your garden building, to ensure all your belongings and any valuable equipment is safe. Our uPVC doors feature an industry leading 12-point locking system. Meanwhile, the windows feature multipoint locks with secure key locking handles.

Our 12-point locking consists of four shoot bolts, three mushroom headed espagnolettes, three hook bolts, a locking latch and a 6-pin euro cylinder. The windows feature a multi-point locking system consisting of mushroom-headed espagnolettes which move in opposite directions into metal keeps. Why would you risk your possessions by using less?

So, if you are comparing garden buildings, don’t forget that our uPVC windows and doors offer additional security benefits!

Insutry Leading Multipoint Locking on Windows & Doors Fully Insulated Secure windows

Unlike some, we only use full-length cuts of shiplap cladding on our garden offices, which comes in a substantial thickness of 15mm. The advantages of using shiplap cladding is it is robust and sturdy.

Our cladding interlocks, creating a strong watertight bond that allows rain to run off the office quicker, it also creates an attractive, professional appearance, that’s certain to wow potential clients if you’re running your business from home.

15mm Shiplap on garden offices

Ventilation is essential for the longevity of the Garden Building. This is to ensure airflow and minimise moisture at all times. We have provided ample vents to ensure that condensation is never a problem. Some competitors charge you extra for these or do not even offer them.

Vents Included with cabins

Get your garden office up and running quickly and easily thanks to the full panels provided. No need to waste time building up walls or fixing doors together.

DIY Garden Offices Easy Build Panel System

When constructing your log cabin, you do not need to worry about putting our timber windows together, as they come preassembled. So you simply need to slot them in, and fit the finishing touches. After all, we take pride in our DIY-friendly designed products. Many competitor products require you to painstakingly construct the windows and other hardware, such as window trims, and install the glass.

Did you know? You can also add a little character to your timber windows with some stylish Georgian bars, which we supply as standard. However, this is entirely optional and up to you. Not all products offer Georgian bars, so be sure to check the product specification.


Dunster House Preassembled Windows, Doors and Hardware


Competitor Non Assembled Windows, Doors and Hardware

Please note: If you upgrade to uPVC Windows and Doors, the glass is not pre-fitted.

All our garden buildings have been designed on the basis that any competent DIY customer should have no problem installing a product themselves in a short amount of time. You do not have to be an expert at DIY to build a Dunster House garden building, as we do provide you with comprehensive pictorial instructions. We totally understand that DIY is not for everyone therefore, you may want to consider getting in touch with a local carpenter or handyman to install it for you. But before you do, check out our construction video and decide for yourself!

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We recommend a flat, level concrete base at least 100mm bigger on each side: e.g. A 4m by 3m building would have a base of 4.2m by 3.2m See more details here.


This garden room is well insulated, but a small electric or fan heater is a good idea to keep the building warm inside. If you choose to install electrics, speak to an electrician about heating.


The Dominator Garden Office contains floor, roof and wall insulation made from SF6 SuperFOIL, which is proven to retain heat better than polystyrene or rockwool. The Dominator also features 28mm double glazed units to aid in retaining heat.


We offer a genuine 10-year guarantee against rot and insect infestation on all pressure treated timber.


No, we do not have any showrooms or display sites. All business is completed online and via our website. If you do have any queries that haven’t been answered with the information provided online, please feel free to call our sales team on 01234 272445.

U-values tell us about the heat loss properties of the material you are measuring. The lower the number, the better insulated the Garden Building will be. Find out more here.

We recommend a flat, level base at least 100mm bigger on each side. e.g. A W4.0m by D3.0m garden building would have a base of 4.2m by 3.2m See more details here.

Often, an additional cost is buried within the price when offering finance, thus making your purchase higher priced. This is the reason we do not offer finance and feel that it would not be beneficial for our customers or us. However, we have come up with an alternative method for you where you can use a 0% interest-free credit card to pay off your purchase. For more information, see this article: Do we offer finance?

Dunster House commit to continuously improve the sustainability level of our sourcing, by favouring stricter more credible certification and verification standards, and sourcing requirements. We are committed to avoiding sourcing from unknown or unsustainable sources.

Where possible, Dunster House are committed to procuring wood products that have been certified against credible, internationally recognised standards for good forest management, to ensure that material originates from well managed forests.
In line with this, we preference products certified to the standards of FSC (Forest Stewardship Council) and PEFC (Programme for the Endorsement of Forest Certification).

What about illegal timber?

Dunster House are committed to sourcing only material that is produced, processed and traded according to applicable legislation.

What is your Environmental Responsibility policy?
Dunster House are committed to promoting responsible stewardship of the environment and its natural resources. We are committed to lessening the impact on the environment caused by our own activities, and those of our suppliers.

Do you have a Supply Chain Management policy?
Dunster House will ensure that information about suppliers and material is gathered as part of the RPP. We will ensure regular engagement with our suppliers to ensure compliance with UKTR requirements, working with them to ensure continuous improvements. We will also specify that, wherever possible, that material sourced is covered by FSC and PEFC, to ensure responsible forest management.

Yes, we do! Some postcode restrictions do apply however we are pleased to be able to deliver to many parts of Scotland.

For more information – Where Do We Deliver?

We do not currently offer installation. All our garden buildings have been designed on the basis that any competent DIY customer will have no problem installing a product themselves in a short amount of time.

You do not have to be an expert at DIY to build a Dunster House garden building, as we do provide you with comprehensive pictorial instructions. Also, if you prefer video tutorials, we do have a selection of videos on YouTube which will support you in building your product.

We totally understand that DIY is not for everyone and it can be very overwhelming to start building your own garden product. Therefore, you may want to consider getting in touch with a local carpenter or handyman to install it for you.

If you do take on the challenge to put your garden building together, we are always here to help. Do not hesitate to contact us at any stage of putting your product together and we can provide you with all the assistance you may need. Contact our customer service team via email at [email protected].

Owing to the multitude of possible configurations available for power and lighting we have left these offices for customers to supply and create their own, exactly how and where they want them.

This Garden Office contains floor, roof and wall insulation. The type of insulation we use is called Polyisocyanurate, which is proven to retain heat better than polystyrene or rockwool. This Garden Office also features 28mm double glazed units to aid in retaining heat.

Due to the unique design of a Dunster House product, in the vast majority of cases our garden buildings can be installed without the need for planning permission.

However, there are a few other factors to consider:

As all properties are different in size, shape and style we can only advise based on how we have designed our products, not on your property.

When to consider planning permission:

  • If the garden building exceeds over 2.5m tall – the majority of Dunster House buildings do not exceed this.
  • If you intend on putting an outbuilding in front of the main elevation of your property (as it was originally built or as it was on 1st July 1948) will require Planning Permission.
  • If you live in a listed or graded building
  • If you live in a designated area such as areas of outstanding natural beauty, national parks, world heritage sites and conservation areas.
  • If there is a possibility that over 50% of your garden would be taken up by outbuildings.

Click here for more information on Garden Building Planning Permission in the UK.

Still not sure?

If you are still in doubt, we highly recommend getting in contact with your local authority before making a final purchase.

It is 2.48m (8' 1")

A Garden Office is a garden building used to create an office away from your home, separating your work life from your home life.

A Dunster House Garden Office is made from slow-grown spruce or wood polymer composite, double glazed 4mm toughened glass, and polyisocyanurate insulation (SuperFOIL on our Dominator range), creating a thermally efficient, smart looking product.

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dominator 5.5 x 3.5 garden office measurements
  • Please Note: All sizes quoted are nominal
  • Overall External Dimensions: 5.55m x 3.68m (18' 2" x 12' 0")
  • External Width: 5.50m (18' 0")
  • External Depth: 3.33m (10' 11")
  • Internal Width: 5.30m (17' 4")
  • Internal Depth: 3.18m (10' 5")
  • Internal Area (m2): 16.85m2
  • Ridge Height: 2.48m (8' 1")
  • Internal Eaves Height: 2.09m (6' 10")
  • Roof Thickness: 0.34m
  • Roof Covering Options: Superfelt Included as Standard
  • Overall Wall Thickness: 75mm
  • Floor Thickness: 19mm Tongue & Groove
  • Framing: 45mm
  • Door Walkthrough Height: 1.82m (5' 11")
  • Door Walkthrough Width: 1.55m (5' 1")
  • Glazing Material: 4mm Toughened Glass
  • Glazing Options: 28mm Double Glazing Included as Standard
  • Gaskets: On all Windows and Doors
  • Timber: Slow Grown Spruce
  • Floor Bearers: Pressure Treated for Longevity
  • Please Note: All fixings needed for assembly are supplied
  • Approx. DIY Assembly Time: 2 Days* *This is an approximate time only, based on 2 people. Assembly time may vary depending on season/weather conditions, foundation type, ability of those constructing, etc

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Delivery Information

* Free delivery on orders over £200.

We deliver our products to the mainland United Kingdom (England, Wales and most of Scotland). Some exceptions apply; these are illustrated on the map below.

Postcodes affected include:

  • TR
  • TQ6, 7, 8, 9
  • EX19, 20, 21, 22, 23, 38, 39
  • LD
  • PL10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35
  • SA
  • KW
  • HS
  • ZE
  • KA27, 28
  • IV1, 4, 6, 7, 8, 9, 10, 11, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 63
  • PA20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 80
  • PH32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44

Dunster House delivery map

Green – Free Assisted Delivery

Red – We are unable to deliver to these areas.

Purple – For orders to Ireland & Northern Ireland, please visit our Distributor in Ireland here.

Delivery Service

All of our products are delivered using our own fleet of vehicles, not sub-contractors. We have a large number of vehicles dedicated to delivering our quality products so we can guarantee maximum care is taken during the delivery process.

Our deliveries take place Monday to Friday between the hours of 8:00 am and 6:00 pm.

When the delivery vehicle is unloaded, it is important that you check to make sure all of the items and instructions have arrived and are correct. You will also receive a component list to check your items against. If anything is missing or damaged, it is essential that you note this on your paper work when you hand it back to the delivery driver.

Prices for our delivery services can be found on individual products.

Please note that goods will be delivered to the first point of contact at the front of your property e.g. on your driveway. This must be within 20m from the delivery vehicle (Safely Parked at Kerbside). Our team will be responsible for assessing the risk of carrying out delivery upon arrival at the property.

Should you require further information on our assisted delivery services, please click here to read our Terms and Conditions, alternatively you can contact a member of our Sales Team.

See the locations we deliver from.

Q: Where can I find more information?

A: If you have any questions regarding your delivery, you can telephone our Dispatch Team. Contact details for the Dispatch Team of your nearest branch can be found on your order confirmation. If you need to track your delivery or access your manuals in advance of your delivery, you can visit the Customer Log-In Area of our website.

Thank you for taking the time to read about our terms and advice during this period. We hope you can enjoy your Dunster House garden product for many years to come.

Why Buy From Us?

Buy with confidence! Established for over 30 years, you can rest assured of our knowledge and experience as industry leaders.

On pressure treated timbers*. We don’t dip-treat our timber unlike some competitors. Dip treatment isn’t as effective at protecting against rot and infestation!

All products are uniquely designed and of high quality with many industry leading features you will struggle to find anywhere else!

A UK company and family run business. Our products are designed  and distributed from our 11 UK distribution centres.

Many have bought from us over the last 30+ years due to our superior specification and the fact that our products are designed with the DIY market in mind.

Free delivery on most products*. Delivered to you by our own fleet of vehicles and dedicated drivers.

Inspiration/Customer Stories

Dean’s Garden Cinema Room

View Case Study

Ed’s Garden Music Room and Home Office

View Case Study

Andy and Rose’s Garden Games Room

View Case Study

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† Reference to Price on 22nd December, 2023

Dominator INSULATED Garden Office

From £7,229.99 £7,649.99
Save £420