Factors in the Garden Room with Bathroom Cost

While many contractors will provide rough prices based on the footprint of your garden room, it’s impossible to get an accurate quote without considering all of the variables within your garden room project.

Cost factors will include:

  • How large the garden room is – that could be a small structure around the size of a garden shed up to a multi-storey luxury log cabin! (Learn more about the cost of brick sheds and log cabin costs).
  • Whether you want a modular garden room (built offsite) or a bespoke design crafted at your property.
  • The materials you choose – garden rooms can be prefab or custom, brick or wood, and with any variety of choice from roofing materials to glazing.
  • Design – you can usually opt for doors and window choices even with a prefab garden room, which will depend on what you wish to use the space for.
  • Interior decorating – plastering, cladding, carpentry and any joinery work will all add to the cost.
  • How much plumbing work you need. Your bathroom might be a simple WC for use in a home office or could be a standalone bathroom with a tub and shower for regular use.
  • What sort of electrical work you need – garden rooms with mains sockets, lighting, Wi-Fi connections etc., will typically cost a little more.
  • External works, such as turfing, decking, or creating a pathway from your main property to the garden room.

Materials can be a significant cost element, as a timber construction will carry a different budget than a brick and mortar garden room. You can also choose between the thickness of the walls, floor and ceiling, needing a thicker insulated shell for a garden room to be used for sleeping in.

Exterior wall cladding is often tongue and groove and can be pre-treated or stained to any colour that matches the style of your property.

Glazing is also a big price element, with double or triple glazing far more energy-efficient but costing more than single glazing. You would usually need at least double-glazing for a garden room being used as an office or expected to be used throughout the year.

To demonstrate how widely prices can vary, the below table shows some garden room construction factors and the average UK cost:

Garden room build element Average cost
Mini garden room self-assembly kit £2,650
Labour charges for two people, for two days £690
Deck base materials £520
Insulation for the roof and floor £630
Electrical wiring £180 – £250 per day
Fitted roofing £650
Pre-painted door and windows £260 each
Painting of internal walls £290 each
Site preparation works £150

Other Budget Considerations in Building a Garden Room

The size of your garden room, what it is built from, and what functionality it needs to have will all be primary budget drivers.

Modular garden rooms are built offsite and delivered readymade, but costs could still include clearing the space, laying a foundation if necessary, and erecting the garden room ready for use.

You’d be looking at between £750 to £1,500 per square metre, but then you also need to budget for the electrical and plumbing costs to install all the wiring and piping.

If you wish to have a fully functioning bathroom in your garden room, you’ll likely need to book a Boiler Inspection to ensure your central heating has the capacity. Many homeowners also book a Hive Installation to control the heating and hot water in the garden room from inside the house. It may also be an ideal time to research the cost of outside tap fittings, as the garden room may provide a new space to install a handy external tap to your property.

Should you wish to use a garden room year-round as accommodation or a workspace, you might also need to look at the Cost to Move a Radiator or fit a new one in the outside space.

The good news is that if you’re comparing an extension to a garden room, the overall costs are likely to be less. Small garden rooms won’t require as robust a foundation as an extensive building, and given that the construction is detached from the property, it is usually much faster to build and cuts down on labour costs.

Finally, your finished garden room will need to be kitted out. You might need curtains for the windows, flooring, carpeting, rugs, seating, desk space, light fixtures, storage shelving and security locks to ensure your garden room is safely secure when vacant.

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Quote Breakdowns for a Garden Room with Bathroom Cost

Most tradespeople quoting for a garden room with a bathroom will provide a detailed, itemised quote to explain exactly what works are included. You can usually see a breakdown between the cost of their labour and the charge for the materials.

For example, a quote might be shown as:

  • The number of hours labour required x number of tradespeople x number of days.
  • Materials cost for bricks, wood, timbers, roofing and concrete.
  • Prices for glazing and doors.
  • Quotes for the bathroom fittings and plumbing charges.

Garden rooms can be pretty pricey to build, although they are one of the most cost-effective ways of expanding your living space – so it’s essential you check the quote thoroughly and ensure everything is included.

VAT will be charged at 20% by any registered contractors, so you must check whether the price is inclusive or exclusive before agreeing for work to begin.

Any additional works such as plumbing and wiring are usually carried out by a subcontractor with these professional skills. Therefore if this work isn’t included in the garden room price, you’ll need to hire contractors separately for this project element.

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What are the Benefits of Building a Garden Room?

Your garden room with bathroom cost is almost sure to add value to your property. Garden rooms mean that your garden is used to its full capacity, and you have a dedicated office space or play area.

Benefits include:

  • Extra living space, ensuring you can stay at home without needing to move. Garden rooms can be much cheaper than needing to upgrade to a larger property if you need extra bedrooms, guest accommodation or room to expand as your family grows.
  • Privacy, with a garden room acting as a play area, home office, business premise, workshop or studio without causing noise disturbances in your property or being disturbed by family life.
  • Providing a separate living space for a family member – garden rooms with bathrooms are a great way to provide an annexe for an elderly family member as an alternative to assisted living. This purpose means they retain independence and privacy and yet are close to relatives should they need any assistance.
  • Speed – garden rooms are fast to install and cause minimal disruption since the work is carried out away from the house. The time required can be as little as a week or two but can be closer to a month for a custom brick-built garden room, depending on the roofing and insulation materials required.
  • Flexibility  – you can adjust your garden room design to your style and tastes, with options such as underfloor heating, internal decor and stains, finishes and configurations to suit your property and garden.

Garden rooms can be pretty pricey to build, although they are one of the most cost-effective ways of expanding your living space – so it’s essential you check the quote thoroughly and ensure everything is included.

FAQs - Building a Garden Room

Let’s run through some of the most popular questions about building a garden room with a bathroom!

Do I Need Planning Permission to Build a Garden Room with a Bathroom?

Basic garden rooms don’t tend to need planning permission provided they aren’t over 50% of the outside space, don’t impact a boundary with a neighbouring property and aren’t over a certain height.

However, if you’re installing a bathroom or kitchen or intend to use the garden room as living accommodation, you will need permission.

A simple WC room won’t usually require permission. Still, it’s vital to consult your local planning department to ensure your garden room build falls under the Permitted Development category should you be in any doubt.

The rules for outbuildings and Permitted Development are:

  • The construction cannot be over 2.5 metres high at the eaves.
  • The maximum overall height is three or four metres depending on the shape of the roof.
  • It cannot be within two metres of a property boundary – or if it is, it must not be over 2.5 metres tall.
  • It cannot take up more than half of the land.
  • It may not have a veranda or balcony, and raised decking is limited to 300 mm.

Can I Use a Garden Room with a Bathroom as an Extra Bedroom?

Yes, but you will need planning permission to build additional living accommodation in your garden. The structure must also comply with building regulations standards – an experienced contractor will ensure the building work meets regulations and sign it off as compliant.

Any building where somebody sleeps needs to adhere to building regulations to ensure the structure is safe and complies with rules about ventilation, insulation, energy-efficiency and stability.

It is possible to modify an existing garden room or outbuilding to make it fit for sleeping in.

Will a Garden Room with a Bathroom Add Value to My Property?

Almost certainly, yes. One of the benefits of a garden room is that you can use it for multiple purposes.

For example, if you have an outdoor home office with a bathroom and come to sell your home, this space could be used as a home gym, a guest room or a playroom, opening it up to more potential buyers.

If the new construction takes up 50% of your garden, you will need planning permission. Still, it would be best to consider whether there is sufficient land to support a structure of this size without detracting from the volume of outdoor space available.

For smaller gardens, a compact garden room is a great way to add value and make use of a corner of the garden that isn’t being used for other purposes.

Can I Put a Toilet in a Garden Room?

You can indeed. The simplest way to install a WC is to connect the structure to the mains water supply and sewerage system as an extension of the pipework in the home.

In some cases, a contractor might advise you not to connect to the mains supply, and install standalone plumbing, or use water heaters or tanks for heating.

Alternatives include dry toilets or eco-toilets, which use a soakaway system rather than mains pipes. Note that if you are building a garden room with a bathroom or adding a toilet to an existing outbuilding, you will need to ensure this complies with building regulations.

Planning isn’t specifically needed for a toilet, but a larger garden room being used to run a business will need approval. If you opt for a pent roof, it must be under three metres high to be exempt from permission, or under four metres high if your garden room has an apex roof.

Is a Garden Room a Good Investment?

If you need more space or a dedicated area away from the main property, a garden room can add as much as £23,000 to the saleable price of your home, often recouping the outlay relatively quickly.

Should you need more space, a garden room is substantially cheaper than building an extension, and if it is a permanent brick structure will last just as long as the main house.

The average garden rooms add at least 5% to your home’s value, depending on how large it is, whether you have mains water and electricity connections. The value will also depend on whether there is planning permission in place to enable it to be used as a small business premises or sleeping accommodation.

Rich Crossley
Having spent 30 years working all over the world for top-tier investment banks, I’ve owned and developed houses all over the world – Europe, the US and Asia. I’m now based back in the UK and involved in the property industry – oh, and I’m a keen DIY enthusiast!
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