Cheap Garden Rooms: What 19mm Walls Really Get You

Cheap garden rooms are easy to find and easy to get wrong. The budget end of the UK market is dominated by one number, the wall thickness, and it is the number that decides whether you have bought a year-round office or an expensive shed. A 19mm building and a 72mm building can sit on the same listings page under the same heading, and they are not the same product.

This is a buyer’s guide to spending less without ending up with a room you stop using in November. It covers what each build type actually gives you, what the advertised price leaves out, where the rules bite, and how to judge a cheap building on spec rather than on the photograph.

What the wall thickness actually tells you

Budget garden buildings fall into a handful of build types, and the millimetre figure in the listing is a reliable shortcut to which one you are looking at.

Comparison panel of garden room wall build types, thicknesses, insulation and realistic year-round use — What each wall thickness means for insulation and realistic use. Chart by Best Garden Room. | Chart by Best Garden Room. Sources: published specifications from Waltons, Garden Buildings Direct and Quick-Garden, September 2026.

Single-skin log cabins, 19mm to 28mm. Interlocking timber logs with nothing between you and the outside. Garden Buildings Direct filters its log cabins at 19mm, 28mm and 44mm cladding thickness, and the thinner two sit firmly in the storage and summer-use category. No insulation, and none intended.

Thicker single-skin, 34mm to 44mm. Warmer, more solid, and still uninsulated as sold. Quick-Garden lists 34mm, 44mm and 66mm wall options and separates plain walls from “34mm plus cladding” and “insulated, 34mm plus cladding”. That distinction is the important one, and most retailers are less clear about it.

Double-skin insulated, 66mm to 72mm. Two timber skins with insulation between them. Waltons quotes 72mm double-skinned walls on its insulated garden rooms, rising to 100mm on its Sherwood range, with tongue and groove walls and roof. This is where a building becomes usable as an office through a British winter without the heating bill making you regret it.

Insulated timber frame, 100mm and up. A proper stud wall build-up with insulation through the frame. More expensive, and the cheapest to run once it is up.

Nothing forces a manufacturer to insulate at all. An outbuilding that qualifies for the building regulations exemptions below is not subject to Part L, so there is no minimum thermal standard a garden room has to meet. The wall number is your only quick guide, which is why it deserves more attention than the interior photograph.

What the advertised price does not include

The headline figure on a budget garden room is usually the building. Several things it needs are quoted separately, and they are what turns an apparent bargain into a mid-range spend.

The base. Concrete slabs, a poured pad or ground screws. A building sitting on an uneven or damp base will twist, and doors that used to close will stop closing.
Electrics. Almost never included. Garden Buildings Direct warns on its own listings that installing electricity may count as a modification to the building and is undertaken at your own risk, which is a guarantee point as well as a safety one.
Insulation, if the build does not already have it. Retro-fitting into a single-skin log cabin means losing internal floor area and doing the work properly enough not to trap moisture.
Treatment. Untreated timber needs a first coat quickly and recoating on a cycle. Pressure-treated timber costs more up front and less afterwards. Garden Buildings Direct extends its 10 year guarantee to 15 years on pressure-treated buildings.
Assembly. Some budget buildings are delivered flat-packed for you to build. Waltons advertises free installation and delivery on its insulated garden rooms, which is worth reading carefully when comparing two prices that look close.

Glazing undoes a good wall

A well-insulated wall next to a large single-glazed window is a well-insulated wall with a hole in it. Glass is the weakest part of the envelope in almost every garden building, and the budget end of the market is where single glazing still turns up.

Check the doors as well as the windows. Full-height glazed doors are the feature that sells the photograph and the component that loses the heat. If a listing is quiet about glazing while being loud about wall thickness, assume the glazing is the weaker half.

The rules you cannot spend your way around

Most garden rooms go up under permitted development rather than a planning application, but permitted development has hard limits. According to the Planning Portal, an outbuilding must be single storey with a maximum eaves height of 2.5 metres and a maximum overall height of 4 metres for a dual-pitched roof or 3 metres for any other roof. If any part of it sits within 2 metres of a boundary, the whole building is capped at 2.5 metres overall. It cannot go forward of the wall forming the principal elevation, and no more than half the land around the original house can be covered by buildings.

Verandas, balconies and raised platforms above 0.3 metres are out. On designated land, including National Parks, the Broads, Areas of Outstanding Natural Beauty and World Heritage Sites, a building more than 20 metres from the house is capped at 10 square metres, and building at the side of the property needs permission. Anything within the curtilage of a listed building needs permission full stop.

Building regulations are separate. An outbuilding under 15 square metres of floor area is generally exempt if it is single storey, detached and has no sleeping accommodation. Between 15 and 30 square metres it can still be exempt if it also sits at least 1 metre from the boundary or is built substantially of non-combustible material. Above 30 square metres, approval is normally required.

Electrics are the exception to all of this. In England, installing a new circuit is notifiable work under Approved Document P, and running a supply from the house consumer unit to an outbuilding is a new circuit. It needs a registered competent person or a building control notification, whatever the size of the building it is feeding.

Where cheap is genuinely fine

Not every use needs an insulated building, and paying for insulation you will not use is its own waste of money.

Storage, tools and bikes. A 19mm or 28mm cabin is the right answer. Spending more buys nothing.
A summer studio or garden bar. 34mm to 44mm, treated properly, used from April to October.
Occasional hobby space. Thicker single-skin plus a portable heater works if you are in it for a few hours at a time rather than eight hours a day.

Cheap stops working the moment the building becomes a daily workplace. A room you sit still in for a working day in January needs insulated walls, insulated roof and floor, decent glazing and a power supply, and there is no version of that which comes out of the bottom of the market.

How to judge a cheap garden room before you buy

Work through the listing rather than the photographs.

Find the wall thickness, and find out whether that figure is single skin or includes insulation. If the page does not say, ask.
Check whether the roof and floor are insulated too. A 72mm wall under an uninsulated roof is a poor trade.
Check the glazing: single or double, and on the doors as well as the windows.
Check the timber treatment and what the guarantee actually covers. Anti-rot cover is not the same as a structural guarantee.
Add the base, the electrics and delivery to the headline price before comparing anything with anything else.
Measure against the permitted development limits above, particularly the 2.5 metre cap if you are building near a boundary.

Buying at the bottom of the market is a reasonable decision when the use matches the build. It goes wrong when a building sold on price is asked to do a job that needed spec. For more on where the next price band takes you, see the rest of Best Garden Room.

Frequently asked questions

What is the cheapest type of garden room?

A single-skin log cabin at 19mm to 28mm wall thickness is the cheapest garden building sold as a garden room. It has no insulation, so it suits storage and summer use rather than a year-round office. The cheapest genuinely year-round option is a double-skin insulated building at around 66mm to 72mm.

Do cheap garden rooms need planning permission?

Usually not, because most fall under permitted development. The limits are the same regardless of price: single storey, 2.5 metre maximum eaves, 4 metres overall for a dual-pitched roof or 3 metres otherwise, and 2.5 metres overall if any part is within 2 metres of a boundary. Designated land and listed building curtilages have tighter rules.

Can you insulate a cheap log cabin later?

Yes, but it costs internal floor area and has to be done in a way that does not trap moisture against the timber. Some retailers sell the building with cladding and insulation as an option, which is generally the cleaner route. Check whether doing the work yourself affects the guarantee before you start.

Is a cheap garden room warm enough to work in during winter?

Not if it is single skin. An uninsulated cabin loses heat faster than a portable heater can replace it economically, and condensation becomes a problem as well as cold. For daily winter use you need insulated walls, roof and floor, and double glazing.

Why do budget garden rooms have no minimum insulation standard?

Because an outbuilding that qualifies for the building regulations exemptions, broadly under 15 square metres, or under 30 square metres with the boundary and materials conditions met, is not subject to Part L. Nothing obliges the manufacturer to insulate, so the specification is entirely down to what you check before you order.

Does a cheap garden room add value to a house?

A well-built, insulated, powered room used as an office is a selling point. A single-skin cabin reads as a shed to a buyer and to a surveyor, whatever it was marketed as. The build quality and the power supply matter more to value than the floor area does.