Garden room cladding: cedar, larch, composite, charred

Why cladding matters

Cladding is the outside skin. It protects the wall build-up from rain and sun, and it is what neighbours see. It also decides how much maintenance you do over the years.

Most garden room builders offer a short list of finishes. Ask to see a sample, and a finished room that is a few years old.

Western red cedar

Cedar is the classic garden room cladding. GreenSpec classes North American western red cedar as durable under BS EN 350-2, if only heartwood is used. It gives expected service life of 40 to 60 years. British-grown cedar is rated moderately durable.

• It moves little, which helps boards stay flat.
• It is soft and brittle, so keep it away from places where it will be knocked.
• Its natural oils corrode ordinary steel, so it needs galvanised or stainless fixings.

Cedar is often chosen for a garden office.

Larch

European larch is classed as moderately durable. GreenSpec gives an expected service life of 30 to 40 years. Quality varies by grade, so ask which grade the builder uses. Siberian larch is described as higher quality with fewer knots, but it costs noticeably more.

Stainless steel fixings are recommended. Larch is harder than cedar, so it suits places where the cladding may get knocks, such as a garden gym beside a path.

Timber goes grey. Plan for it

All untreated timber species fade to a silver-grey. GreenSpec puts this at around five years, and says the change is often uneven. Some people love it. Others do not.

You have two options. Leave it alone and accept the colour change. Or treat it with an oil or stain. GreenSpec warns that treating and coating timber dramatically increases the need for frequent maintenance. Ask the builder which finish they offer and how often it needs redoing.

Composite cladding

Composite boards are made from wood fibre and plastic. They are sold as low-maintenance and they keep one colour. Check the following with the supplier.

• The fire classification of the board.
• The length of the manufacturer's guarantee and what it covers.
• How the colour is expected to age.
• How the boards are fixed and allowed to expand.

We have not tested any brand and make no claims for one. Ask for data sheets.

Charred timber

Charred timber, often called shou sugi ban, has a burnt surface that gives a dark, textured finish. Suppliers say the char layer helps protect the board. Sources disagree on how well it wears on boards that face hard rain and wind, and the result depends on the species. Ask the builder for a room that has been up for several years.

Treat any service life figure from a supplier as a sales claim. Ask for the fire classification of the finished product.

Cladding and the rules

Permitted development sets limits on height, position and size, not on material. In a conservation area, a National Landscape or near a listed building, the council may care more about how the room looks. See our conservation area and Chilterns guide.

Material matters for fire when a room is close to a boundary. Between 15 m² and 30 m², an outbuilding with no beds is exempt from building regulations if it is at least 1 m from every boundary or built substantially of non-combustible materials. A timber-clad room usually relies on the 1 m distance. See garden rooms near a boundary.

How to choose

• Want the classic look and can live with grey? Cedar or larch, untreated.
• Want the colour kept? Cedar or larch with a regular oiling plan, or composite.
• Want a dark modern look? Charred timber, with a good supplier.
• Want the least work? Ask about composite and about a pre-finished timber.

Cladding changes the price. See the garden room cost calculator and how a price is built. Local examples of rooms are in Beaconsfield, Northchurch and St Albans.

Questions to ask about any cladding

• What is the species or product name, and where does it come from?
• Is it heartwood? Durability figures apply to heartwood only.
• Which fixings are used? Cedar and larch call for stainless or galvanised fixings, as GreenSpec notes.
• Is it fitted so air can move behind it and rain can drain?
• What is the finish, and when does it need redoing?
• What does the guarantee cover?

Ask for a sample, and keep it outside for a week to see how it looks wet and dry.