Tips for designing and making outdoor furniture

Officially it’s not Spring in the UK until March, but the warmer days are on their way – as heralded by the Spring daffodils popping up all around the school.

Our furniture students are ahead of the game and have spent the winter making some beautiful garden furniture from which the Spring sunshine can be enjoyed. Gordon, Rosie and Mark have all designed and made garden benches; a swing bench, a steam bent bench and a Japanese inspired bench!

Designing with purpose in mind, this blog looks at the design considerations that will extend the longevity of any furniture exposed to the elements.

1)      Choosing the Right Wood/Materials

If you are making your furniture from timber, there are several species that are naturally more durable to outdoor conditions. Hardwoods are superior to softwoods for outdoor furniture, with Oak and Chestnut being favoured by the Williams and Cleal students.

A quick browse of the internet, reveals Teak dominating the garden furniture market. Teak has long been considered the gold standard for outdoor furniture. This is because Teak is one of the strongest hardwoods, versatile to work with, and resistant to rotting, insect damage and acid damage. For this reason, it is a prized material amongst the boat and construction industries.

However, we can’t talk about Teak without first addressing issues around sustainability. Teak is an endangered species with much of the natural population significantly depleted. The supply of Teak is now sustained through managed plantations, but plantation teak is considered less dense and more susceptible to insects and rot than Teak from natural forests. It is also expensive. Even Teak alternatives like Oroko and Idigbo are now being listed as vulnerable due to a population reduction of over 20% in the last three generations. As such Favinha, Guariuba, Tatajuba and Eucalyptus from fsc certified suppliers are the next best alternatives to use.

We also need to credit our native hardwoods like Oak and Chestnut as superior species for designing and making Outdoor furniture from. Again, we only need to look to Oak’s long history of use in boat making and barrel making to see that it has long stood the test of time against the elements (and weathered many at storm as the material of choice for old English war ships.) When designing outdoor furniture, it is always worth asking modern boat building yards what species they are using!

Oak and Chestnut are significantly less porous than other species, with tyloses filling the pores of the wood and preventing moisture from penetrating. Both species also have a very straight grain and dense structure. They are rich in tannins which prevent decay and rot by precipitating enzymes and proteins that are harmful to bacteria, fungi and pests that might damage or accelerate rotting. These hardwoods should be protected with a sealant, but if well maintained and looked after they should last many years.

2)      Design Features to aid water run off – Drip Channels, Joint placement, Fixings and Fittings

When designing outdoor furniture, close attention should be paid to features which are going to aid water run off and avoid moisture pooling on the surfaces of the wood. Ways of doing this are:

-          To incorporate angles to your furniture which promote moisture run off

-          To design your outdoor furniture in a way that shields essential joints from the worst of the weather, so that moisture isn’t directly seeping into joints or collecting in these areas.

-          Add a drip channel in areas hidden to the eye, but where water is likely to collect or track – like the underside of a bench seat. This small channel prevents water clinging to the underside of your bench by capillary action, forcing it to drip off to the ground instead.

-          Pay attention to the feet of your outdoor furniture as prolonged contact with moist or damp surfaces is likely to accelerate the deterioration of your furniture. With Rosie and Mark’s benches, some simple nylon feet elevate the bench legs so they are never in direct contact with the floor. Not only do they allow rain to drip off the bench legs, but they allow air to circulate and dry under the feet of the furniture. Justin also advocates sealing the feet of your furniture really well with something like Yaught varnish or sealing wax.

3)      Other techniques for prolonging the life of outdoor furniture

You’ll see in the pictures above that both Rosie and Gordon have chosen to scorch parts of their outdoor benches. The reason is not only aesthetic, but also practical. Scorching wood is a really effective way of protecting wood against the elements.

SCORCHING WOOD

Scorching wood is an ancient Japanese technique – known as either Yaki sugi-ita or more commonly in the Western world  - as Shou sugi ban. Scorching vaporises the cellulose in the structure of the wood, which is the carbohydrate that pests, bacteria and fungi seek in wood and it thus renders the wood less desirable to pests, and makes it resistant to rot. Scorching or ebonizing wood also creates a charcoal layer on the surface of the timber which repels water and resists sun damage.

Not only does charring change the cellular structure of the wood, but also the thermodynamic conductivity of the timber. On burning the wood outermost cellulose burns off easily leaving the hard and tough lignin behind – which is much harder to ignite again once the wood has been scorched. Not only is this useful in creating an antibacterial protective layer of charcoal, but it also gives a level of heat and fire protection -  since the lignin is harder to ignite once the primary cellulose layer has expired. Charring therefore makes the wood resistant to heat and fire too.

From an aesthetic point of view, charring gives a permanence of colour that stains and varnishes can’t beat and doesn’t need to be maintained.

PROTECTIVE FINISHES

Depending on which species of wood you decide to use for your piece, a regular maintenance schedule will ensure your outdoor furniture looks good for as long as possible. The most popular advice online advocates washing the furniture using a brush once a year to remove algae and litchens, tilting or covering furniture throughout the winter months as long as it is well ventilated, and there are numerous wood preservatives and UV protection oils available to apply. Additionally, it’s advisable to take any removable upholstery off your furniture after use or in inclement weather to stop water pooling under the cushioning.

Taking these tips into account will help ensure that your outdoor furniture will last for years, decades even if maintained regularly. We are looking forward to seeing Rosie, Gordon and Mark’s benches in their final outdoor locations and we are holding out for a nice summer in 2020 so the benches can be thoroughly put to the test!