Snows Timber produces enough softwood cladding and shiplap each year to cover the Great Pyramid at Giza six times over. Extrapolate that across the UK cladding sector and it gives some idea of market size.

The survey that the Timber Decking & Cladding Association (TDCA) plans to carry out this year will give a clearer picture but feedback from companies suggests the business is strong, and growing.

"Demand is good across our cladding ranges," said Andy Jones, Snows Timber’s northern regional sales manager. "There’s no doubt the upturn in construction is having a positive effect on sales."

He said there was growing demand for cedar and Thermowood cladding across all sectors – private and public housing, garden buildings, schools and hospitals.

"It’s the perception of warmth and connection with nature timber cladding evokes which drives its popularity," said Mr Jones. Summary James Latham plc also reports strong demand, reflecting the growing trend for environmentally-friendly building materials.

"Architects are looking for more natural finishes, natural appearances and sustainable materials and timber very much falls into that bracket," said Richard Mosson, group product manager for cladding.

Demand was particularly strong for design and build housing, he said.

And Brooks Bros (UK) expects timber cladding’s growth to continue, despite competition from other products.

"Larger volumes are being used in both the retail sector and on government projects, such as schools, hospitals and social housing, prompted mainly by government low carbon sustainability initiatives," said group cladding manager Andrew Goto.

When it comes to species, western red cedar remains king in the clear imported species, but others, such as pine, spruce, larch, Douglas fir and oak are also stalwarts and Brooks Bros has over 30 species in its inventory.

However, a big growth area for the industry is also modified timber through thermal treatment – Thermowood – and chemical modification – such as Kebony "Where contractors are concerned, western red cedar is top of their list because of its durability and look," said Mr Jones.

Neale Brewster, Howarth Timber Group’s marketing and product development manager, agrees. "Most architects specify WRC because they like the colour but there’s a wide variation – it can be dark, very light or even insipid. Because thermal products are ‘baked’, you get an even colour across the product."

Thermally-modified cladding was treated throughout, so it didn’t need resealing after fixing or cutting and it weathered uniformly, Mr Brewster added.

Thermally-Modified is hot

Howarth’s thermally-modified range includes redwood, spruce and radiata pine – the latter under the Thermory brand – and hardwoods frake and ash.

The American Hardwood Export Council (AHEC) also recognises the market potential of thermally-modified hardwoods.

"Thermally-modified North American hardwoods can offer a real alternative as a cladding option," said AHEC’s European director, David Venables. "Architects in the UK are beginning to take notice of the potential that these once non-durable species have to offer, having seen evidence of their successful use on cladding projects in America and across the Continent."

Thermal modification enhances timber’s dimensional stability and increases the durability rating to class 1, very durable. The timber is an attractive dark brown through the cross-section and can be left to weather to grey or UV inhibiting oils can be applied. Ash is the most popular species, because of its open grain, but tulipwood is also gaining recognition, said Mr Venables.

"There’s huge mileage in using timbers like tulipwood, which has a smooth finish. It’s like polished walnut or cherry on the outside of your house," he said.

American white oak can also be used for cladding.

"If correctly installed with sufficient expansion gap between boards that are properly fixed using non-corrosive fixings, white oak can achieve a high performance cladding façade," he said.

A "shining example" of this species in use is the European Commission’s Food and Veterinary Office in Ireland, which opened in 2002 and features 10,000m2 of it in external cladding and joinery.

"Thirteen years in the harsh Irish climate shows that this timber is more than suitable as cladding," said Mr Venables.

Pre-finished benefits

While a lot of cladding is still supplied unfinished, some specifiers want to maintain the fresh-out-of-the-box colour of the timber and most companies report a rise in demand for pre-finished product.

However, Nick Taylor, managing director of Silva Timber Products Ltd, stresses that finishing is about more than just aesthetics. "Architects in this country have

misunderstood cladding," he said. "Because species like WRC and Siberian larch are naturally decay resistant, that’s been misinterpreted as not requiring finishing and that’s why you see a lot of cladding that’s gone black or has water staining or uneven weathering. These species don’t rot without a finish but they’ll look better and perform better with one."

Mr Taylor added that finishes with a pigment provided greater protection and the texture of the wood was also important. "Studies prove that when wood has a sawn texture or a sanded texture, which raises the grain slightly, the finish absorption is greater and therefore lasts longer," he said.

Silva Timber will soon launch pre-finished cladding with an eight-year warranty on natural tones and a 15-year warranty on opaque, both backed by Canadian finishes manufacturer Sansin.

Brooks Bros’ Andrew Goto points out that factory-applied finishes offer time and labour savings – and add value.

"Add to the mix fire treatments to Euro Class B or C and intumescent coatings and warranties on some coatings and you see how pre-finishing provides the ‘complete cladding service’," he said.

Howarth Timber has also seen an increase in demand for pre-finished cladding. But when it’s accompanied by a fire retardant, Howarth stresses the need for compatibility between the two treatments and good ventilation behind the cladding.

"If the stain or paint doesn’t adhere to the FR treatment it can bubble, and that can be exacerbated by poor ventilation," said Mr Brewster.

While a finish is often specified to counter the possibility of patchy weathering, some clients, such as Mercia Marina in Derbyshire, want a weathered look from the outset. To achieve this, Howarth brushed thermally modified cladding before applying a finish.

On this project the cladding and decking were both thermally-modified redwood and Mr Howarth believes matching components will become more popular.

Brooks Bros recently introduced Shou Sugi Ban, a traditional Japanese technique of charring the timber, mainly for aesthetics.

PRIME MODIFIED MARKET

For Accoya, cladding is the second most important market in the UK behind joinery.

"Accoya is used where people want timber cladding, but to avoid problems normally associated with it, like distortion of boards, relatively short service life and high maintenance of coatings applied," said Bryan Crennell, Accsys Technologies’ director of sales and marketing.

Accoya has a class 1 durability rating and research by TRADA showed cladding boards could be as thin as 15mm to a width of 195mm without risk of cupping.

"This helps to reduce price per square metre," said Mr Crennell.

A potential area for development is coating systems that are not specifically designed for wood and may offer even longer service life. "Accoya’s stability may allow the use of coatings systems normally insufficiently flexible for use," said Mr Crennell.

Lathams has enjoyed success with Accoya cladding, which it markets under the AccoyaLathamCLAD brand, and it is predicting similar results from Medite Tricoya Extreme, which is supplied by SAM Mouldings. It has the same benefits as Accoya – dimensional stability, durability and it takes a paint finish well – but offers added versatility, according to Mr Mosson.

Medite Tricoya Extreme boards are 4.88m x 4ft wide and can be machined to produce cladding that’s double the width and half the thickness of normal cladding dimensions. This, combined with the ability for a good paint finish, gives architects design flexibility.

Interest in wood composite cladding is growing and some companies, such as Snows Timber, have added it to their offering. James Latham doesn’t stock it yet, but Mr Mosson said it was "definitely on the company’s radar".

The TDCA regards composites as complementary to timber cladding, as long as they’re quality products. And they also benefit the wider timber industry.

"It’s similar to decking – composite materials are put on a wood substructure and you need more wood because you need to place the centres closer together because it’s not as rigid," said TDCA director Janet Sycamore.

While composite products may be nudging in on the market, this year timber cladding will receive a further boost with publication of the new standard cladding – BS 8605. "Architects are becoming more confident in specifying cladding and BS 8605 will help to breathe even more confidence into the market," said Mr Mosson.

It will also reinforce timber cladding’s position as a quality product.

"Customer expectations have changed from one of simply buying a basic machinedto- profile timber section to now expecting a product that offers a complete solution and is fit for purpose," said Mr Goto