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It’s worth checking with your local authority planning department, especially if you live in a listed building, conservation area, Area of Outstanding Natural Beauty, or National Park.
Outbuildings don’t generally need planning permission, so long as:
Rules governing outbuildings apply to sheds, greenhouses and garages as well as other ancillary garden buildings such as swimming pools, ponds, sauna cabins, kennels and enclosures (including tennis courts).
Verandahs, balconies and other platforms (including tree houses/playhouses) require planning permission, with the exception of decking up to 300mm above ground level.
The performance of naturally durable hardwoods can be matched by low-cost preservative-treated softwoods. But not all preservative-treated timber is suitable for use in the garden. Make sure you ask for timber treated to Use Class 4 for any timber that will end up in contact with the ground.
Use external grades fixings, usually hot-dipped galvanized or stainless steel. Further advice on fixings is available in this Timber Trade Topics series.
Use timber capable of giving a service life of at least 15 years. This means either a naturally durable species, such as ipe, iroko, oak, jarrah, balau and Western red cedar, or a softwood that has been pressure-treated to the right level for the job.
Most timber sold for use in the garden has already been pressure-impregnated with wood preservative and may be recognized by its green or mid-brown tint. Check with your supplier whether the timber is suitable for above ground or in-ground contact (see the treated wood Use Class table below):
Modern pressure-impregnated wood preservatives and water-based proprietary products are safe for plants, pets and people unless eaten. If you are using solvent-based preservatives or coatings on sheds or fence panels, follow the manufacturer’s advice and instructions.
Check fence panels are suitably pre-treated, so they won’t need further treatment, unless you want to paint or stain them. Use gravel boards (pressure-treated to Use Class 4) to support the panels off the ground so as to extend their service life. It’s cheaper and easier to replace any failed boards than the panels themselves. Gravel boards will take up any unevenness in ground levels, so the fence panels can simply be slotted into place.
Use Class 4 pre-treated fence posts are available in a range of lengths and sizes. Use a minimum section of 75mm x 75mm – larger for exposed areas or particularly high fences. Incised pre-treated Use Class 4 posts are available with a 15-year warranty.
Consider the suitability of the location, the safety of the ground surface and whether the equipment requires securing (e.g. in concrete). Check the equipment is CE marked and that the packaging states it is manufactured to meet BS EN 71.
Follow the manufacturer’s installation instructions carefully. Avoid sharp edges, rough surfaces and protruding fixings, adding caps to all ends. Use suitable, water-based coatings.
Ideally you should seek specialist advice before designing or building garden play equipment, as you must observe the relevant safety standards. For example, you will need to avoid small gaps that could trap children’s fingers or heads.
There are many different types of timber garden buildings, including sheds, kennels, decks and tree houses. Many are sold in panels that can simply be nailed together. Others, such as summer houses or log cabins, may need screws or coach bolts to fix them together. They will usually be pressure-treated. To ensure a long life:
Don’t burn offcuts from pre-treated timber on a bonfire or barbecue. They should be disposed of in a landfill site, or incinerated in accordance with national regulations.
Other relevant Timber Trade Topics:
BS 1722-11: 2006 Fences. Specification for prefabricated wood panel fences, BSI
BS EN 71-1: 2011 Safety of toys. Mechanical and physical properties, BSI
Timber is the most sustainable mainstream building product. It is naturally renewable. Over 90% of timber used in UK construction comes from Europe, where more trees are grown than harvested (source: TTF Statistical Review 2016).
Softwood and temperate hardwood forests in Scandinavia, Europe, Canada and North America are stable or growing. Growing forests act as carbon sinks; wood products act as carbon stores.
Ask for PEFC or FSC Chain of Custody certification.
See Wood Campus RIBA CPD module Procuring Sustainable Timber for more on timber certification and sustainability and government requirements.