Composite Decking Joists – Information for Architects

Millboard decking – information for architects

Our decking combines the natural beauty of real timber with the high performance of our unique wood-free material. Unlike wooden decking it will not rot, warp or split. Its Lastane® surface is non-porous, which gives high resistance to mould and algal growth and excellent anti-slip properties. With a product that carries a 25 year warranty it is recommended that the subframe system have atleast the same warranty, which timber joists do not offer. Enter our Plas-Pro subframe, a completely wood-free product which will also stand the tests of time.

What does Millboard composite decking look like?

It has the most realistic wood effect of any composite decking. Most people stepping on to a Millboard deck will have no idea it’s not made of real wood.

What is it made from?

Our decking is made from polyurethane resin combined with mineral stone flour to create a resin mineral board (RMB). Other ingredients include high quality colour pigmentation and ultraviolet light inhibitors for durability and lasting beauty.

Composite decking joists – what span to use?

400mm centres for residential applications, 300mm centres for commercial and public realm applications. Millboard decking will cantilever over the end of a joist up to a maximum of 50mm.

Can I butt-joint ends of composite boards tight to the next decking board?

In broad terms, yes, because both expansion and contraction are minimal. The butt joints should be positioned in conjunction with recommendations contained in the installation guide. A maximum of two butt joints before a gap of 2-3mm is recommended.

What fittings should be used with Millboard decking?

Millboard decking can be constructed with screws, just like wood, but without the danger of it splitting. We warrant the use only of our ‘Durafix’ screws. These can be driven in with no pre-drilling required. Our decking’s Lastane® surface will self-heal over Durafix screw heads to provide an instant and very attractive ‘Lost Head’ effect.

Can you use normal wood working tools?

Absolutely. No specialist wood working equipment is needed – you can even saw it by hand. As with all products that create dust when worked, we recommend dust bags on saws and the wearing of dust masks and gloves.

Can the Millboard decking system be used on a flat roof?

In a word, yes. If the roof has a slight slope, use our ring supports or joist shoes to position the joists. For a single ply membrane roof, use our adjustable self-levelling head pedestal systems to spread the load. Both products will raise the composite decking joists above any standing water, prolonging their life while also acting to reduce sound transfer. They also encourage the free flow of water on the roof membrane.

Will Millboard decking fade over time

Millboard has a very high resistance to fading. It contains no wood fibres which typically fade and leave tannins.

How will salt water effect Millboard composite decking?

Millboard is suited to saltwater environments, even when fully submerged.

Can you use composite decking for load bearing applications (i.e. structural)?

It is not recommended to use Millboard in structural applications.

Can you paint/stain it?

There’s no need! Millboard is designed as an ultra-low maintenance product, and paints and stains will not adhere permanently to the surface of the Millboard material in most cases. Clients choose the colour they desire based on the knowledge that they won’t have to coat it to keep its colour. For scrapes and exposed ends, we offer special touch-up coatings in all the Millboard stock colours.

Can you bend Millboard composite decking?

Millboard decking boards won’t bend across their width, but curves can be created by using the flexible edging profiles and fascias.

Are Millboard composite decking products environmentally friendly?

Yes. Because Millboard decking will not splinter, warp or fade in the way wood does, it dramatically reduces the wasteful life cycle of repair and replacement and eliminates the frequent application of environmentally harmful paint, sealers or stains. Millboard decking boards are manufactured with polyurethane resin which outlives timber: up to 35-40 years is typical. This avoids unnecessary replacement, which would use up resources on a broader scale. In addition, the manufacturing process of rigid polyurethane resin uses a much lower energy expenditure (2-6 Mj/Kg) than the thermoplastic process (6-29Mj/Kg) used to produce other composite decking, reducing potential emissions.

How does the price of composite decking compare to softwood decking?

At installation, it is more expensive than softwood decking, but similar in price to a high quality hardwood. The labour cost remains similar. Over a deck’s lifetime, though, the life cycle cost of Millboard decking is considerably less than that of softwood decking, thanks to the reduced maintenance requirement.

What material is used for the sub structure?

Although treated wood can be used, it will usually need replacing long before a Millboard deck will. We therefore offer our Plas-Pro sub-frame system. This is made from 100% recycled plastic, making it impervious to the effects of water or attack by insect larvae.

Does Millboard decking become slippery when wet?

As well as having an anti-slip Lastane® surface, its resistance to algae gives Millboard exceptional anti-slip performance, even in the wet.

How easy is it to look after?

Very little maintenance is required. As the surface is non-porous, dirt, food and drink spillages are not absorbed, as they would be into timber. The simplest way to clean the deck itself is to use soapy water and a brush. It can be cleaned down with a power washer on low power, but this should never really be needed.

View the complete Millboard Collection here or download our Architectural Guide here.