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The quicker and cheaper way to create extra room

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Conservatory Alternative Addrooms Conservatory Alternative Addrooms

Unlike a Conservatory:

Warm Temperature Icon Warm in the Winter
Cool Temperature Icon Cool in the Summer
Raining Icon Sound Insulation When Raining

Features and Benefits

  • Insulated 140mm walls, 65mm roofing, 40mm floor.
  • 28mm double glazed uPVC windows and doors.
  • Low maintenance, durable WPC (Wood Polymer Composite) walls.
  • Cost effective conservatory alternative.
  • 10 year guarantee on pressure treated floor bearers.
  • Secure, industry leading 12 point door locking system.
  • Easy build DIY panel system for quicker install.

Full Specification

28mm Double Glazed uPVC Windows and Doors

28mm Double Glazing

Our Addroom® Garden Rooms have 28mm double glazing in all of the windows and doors. These double glazed sealed units are made using 4mm panes of glass with a 20mm aluminium spacer bar in between to absorb any moisture. This is designed to prevent condensation within the unit, and has been independently tested to ensure this. These sealed units also comply to BS EN 1279 standards, which covers requirements for thermal and sound insulation.

Insutry Leading Multipoint Locking on Windows & Doors

Industry Leading Window and Door Locking

Whatever you choose to use your garden room for, security is important to keep all your treasured belongings and valuable items safe. This is why we include PVCu French doors with an industry-leading 12-point locking system, as well as multi-point locking windows with key locking handles.

Our 12-point locking system consists of four shoot bolts, three espagnolettes, three hook bolts, a locking latch and a 6-pin euro cylinder. Our window locking system consists of mushroom-headed espagnolettes which move in opposite directions into metal keeps.

Addroom Garden Room Easy To Build Panel System

Easy to Build Panel System

Get your Addroom® installed quickly and easily thanks to the full panels provided. There is no need to waste time building up walls or fixing doors together.

Pressure Treated Bearers

Pressure Treated Floor Bearers

Addroom® Garden Room comes with pressure treated floor bearers included as part of the standard kit. This is highly important in helping to maintain a solid foundation for your building, as this is the part in contact with the cold damp ground. Beware of companies that leave the timber untreated, or don’t even supply floor bearers at all for the building to sit on.
Pressure treatment is a costly and time consuming process, but is highly effective in protecting the timber. During the process, wood preservative is forced deep into the timber as moisture is removed. This fully protects the wood, making it much more effective than dip treatment which only coats the exterior surface. All of our pressure treated timber comes with a genuine 10 year guarantee against rot and insect infestation. However, we do recommend you apply a good quality water repellent to the timber to help prolong its life.

Addroom Garden Room Wide Opening uPVC French Doors

Wide Opening French Doors

The wide opening PVCu French doors offer a large walkthrough width, providing easy access for moving items in and out of your garden room. They also allow you to make the most of the fresh outdoor air and natural sunlight.

Low Maintenance WPC Exterior Walls

Low Maintenance WPC Exterior

Possessing all the benefits of plastic and timber combined, WPC (Wood Polymer Composite) is ideal for use on outdoor buildings. It is hard-wearing, resistant to water and requires very little maintenance. The impressive brick effect design on the exterior walls enable you to match your garden room to your house. The traditional red coloured, natural toned brick will give an attractive finish to your garden room that will blend beautifully with your home. Meanwhile, the groove effect finish will give your garden room a more contemporary feel for a modern look.


Modular Addroom Fully Insulated Panels

Fully Insulated with Polyisocyanurate Sandwich Panels

Insulation is important in helping to maintain the temperature inside your garden room, so you can maximise its use all throughout the year. It will help to retain any generated heat inside to keep you warm during the colder months. It will also help to keep the building cool inside during hot summer days. This means you will have a comfortable living space no matter what time of year it is.

All Addroom® Garden Rooms come fully insulated with polyisocyanurate sandwich panels making up the walls and floor of the building. The roof also comes as an insulated sandwich panel with a high density polyurethane core. The walls have a 70mm cavity to increase airflow and ventilation, with two skins of 25mm thick insulation, while the floor is made with 25mm thick insulation. We use polyisocyanurate insulation as it gives high thermal efficiency, and is known to be far superior to alternative materials used by other companies, such as polystyrene, rockwool or bubble wrap.

Addroom Fire Resistant Inner Wall

Fire Resistant Inner Wall

The inner walls of our garden rooms are made using a fire resistant fibreboard for increased protection. This is a hard-wearing material made from recycled paper fibres and Gypsum (Hydrous Calcium Sulphate). The fibreboard is supplied unpainted so you can design and decorate the interior of your garden room to your own individual style. This material is a good surface for paint and is easy to wallpaper.

Insulated Roof Panels Addroom Modular

Traditional Style Insulated Roof Panels

Our Addroom® Garden Rooms come with an easy-to-install insulated roof panel that has an attractive grey slate tile effect appearance. This offers the best performance and aesthetic finish, imitating a traditional design that gives your building a modern look. The 65mm thick insulated sandwich panel provides high levels of thermal efficiency and good sound insulation. It has a polyurethane insulation foam core protected by two sheets of pre-lacquered, galvanised and profiled steel. The upper tiled effect layer is formed by a total of six tiles, not five like others do, as it offers more resistance and insulation capacity. Polyurethane is a high density material with fantastic insulative properties. The lower steel plate is finished in basic white.

The roofing panel boasts a U-value of 0.32 W/m2K. This compares to 2.8-3.0 W/m2K that you might typically see on an old conservatory glass roof where there is air space between the panes of glass.

What is a U-Value? U-values refer to the rate of thermal transmittance through a material or structure – how good a thermal conductor or insulator it is. U-values are measured by the unit W/m2K. The lower the U-value, the better!

The overlapping joining system gives the roof tight connections that help prevent leaks and humidity, ensuring warmth is kept in and doesn’t escape through the ceiling. The high quality roofing system has been subjected to numerous tests and controls to ensure the effective performance of its qualities and characteristics.


What is an Addroom®?

An Addroom® is a fast, cost-effective & convenient solution to home expansion. Addroom® can have numerous uses, such as a garden office, an extra family room, a games room, a music room, a gym… the list is endless. An Addroom® can be the perfect cost-effective alternative to a conservatory.

Why buy an Addroom®?

• Simple panel system designed with the DIY market in mind
• Why move home? Avoid expensive moving costs!
• A useable room all year round unlike some conservatories
• No dirty glass roofing to clean
• An ideal office, playroom, gym and more
• No bricks and mortar, less time, less money

Does an Addroom Require Foundations?

No! Addroom® can be placed on sufficiently consolidated sub-base for the bearers to be placed on such as patio tiles. There’s no need to excavate large footings which can be expensive.

How Much does an Addroom Cost?

Our competitively-priced Addroom® starts from just a few thousand pounds and is likely to cost far less than a brick-built alternative

Does Dunster House Install?

We do not currently offer installation. All our Addroom garden rooms and Addroom porches 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. 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. 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].

How do I Keep my Addroom® Warm?

There are several options available when looking at how to keep your Addroom® warm. Firstly, if you are only planning to use your Addroom® occasionally, we would just recommend putting in a small electric heater in the Addroom®. Usually, you would turn that on 20 minutes before you are going to use it to kill off the chill. However, if you are planning to use your Addroom® all year round for either business purposes or a play area etc, you may want to consider the option of an isolated central heating system. Remember, our Addrooms® are highly insulated for year-round use. See our features tab for more information.

How do I Attach an Addroom® to my House?

All Houses are different some are brick, some are not. We do not therefore supply the fixings, however in the ‘how to build guide’ we show where the fixing screws are to be placed and drilled into your House. This includes the walls the base and the roof.

How do I Make the Addroom® Watertight?

We show in the build guide where to place sealant around the frame including where it meets the House. We also recommend a good flashing be used on the roof. The guide shows where this meets the building and the Addroom®.

Planning Permission

A commonly asked question is whether an Addroom® requires planning permission, or does the Addroom® fall under permitted development for a conservatory?

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 some 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.

Where permitted development for an extension may apply:
• If the maximum ridge height is less than 3 metres (the Addroom® height is 2.99m (9′ 9″))
• If the extension is less than 30 square metres internally (the largest Addroom® internal area is 13.86 m2)
• If the total external depth from the house wall is less than or equal to 3 metres (the Addroom® is 3.00m (9′ 10″))
• If the external appearance is similar to the existing dwelling house (we offer the Addroom® in a variety of pre-painted and unpainted finishes, and use domestic-style uPVC window and door profiles)

You may need to consider applying for planning:
• If you intend on putting an outbuilding on the principal elevation of your property
• 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
• If the external appearance is not similar to the existing dwelling house

Learn more about Planning Permission in the UK

Still not sure? If you require any further information or are in any doubt, please visit the official government website, or contact your local planning authority.

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