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Yellow Balau (Bangkirai) Decking Smooth 21 x 145mm

(exc VAT) (inc VAT)
Price per linear metre £5.55 £6.66
Price per square metre £37.02 £44.42

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Yellow Balau - Bangkirai - is a very durable hardwood, well suited to deck construction. It is one of the most popular species in the UK for hardwood decking. With a mixture of warm colours of golden browns, light browns and pale reddish-browns, Yellow Balau offers a unique colour range which will sit beautifully within a natural environment.

20% off selected lines - excludes 2.44m, 3.05m, 3.66m and 4.27m lengths

At a glance

  • Interlocking grain and fine even texture
  • Hard, heavy and strong timber suited for deck construction
  • Colours vary from yellow-brown to pale red-brown
  • For best results sand and apply a coating at the outset
  • Silva Recommended Finish - Sansin Dec
    Yellow Balau looks best in one of these colour tones...
    Harvest Gold (Natural) | Autumn Gold | Espresso
  • View Grade/Quality information

Please ensure when ordering that you make an allowance for wastage. We recommend adding an additional 10-15% over and above your initial requirements.

Hardwood Decking with interlocking grain and fine even texture

Yellow Balau decking boards are supplied with a smooth face and bevelled edges.

Yellow Balau (pronounced Bal-Ow) - Bangkirai - is a very durable hardwood. It is a hard, heavy and strong timber that is well suited to deck construction.

Yellow Balau decking has an interlocking grain and a fine and even texture. Its colour varies between yellowish-brown, brown and pale reddish-brown. Occasional pinhole and hit and miss is acceptable within the grading rules of Yellow Balau decking.

Storage and Handling 

For best results store your Yellow Balau decking out of direct sunlight and do not expose it to weather before installation.  Keep the boards off the ground by stacking them flat on timbers placed on the ground; this allows air to circulate around the stack.  Cover your deck boards with a waterproof breathable sheet to protect them from sun and rain until you are ready to install them.

Please note, orders placed for 1m lengths will be supplied in random board lengths, dependant on stock availability.

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Case Study

Yellow Balau hardwood decking delivers contemporary look and natural feel

Finishing & Protection

Even though Yellow Balau is highly durable in its natural state we recommend that Yellow Balau decking be finished on all four sides prior to installation to help prevent surface checking, discolouration and cupping.

Why factory coat?

  • Enhances the natural beauty of wood
  • Ensures a consistent finish
  • Applied in factory conditions
  • Long lasting protection against weathering
  • Simple maintenance routine
  • Reduces onsite labour costs

The importance of sanding

As Yellow Balau is an incredibly dense species it is essential to sand the deck boards prior to applying the finish. Sanding opens up the cells on the surface to allow the stain to properly penetrate. This facilitates deeper penetration of the stain for a consistent appearance and longer service life.

What is weathering?

There is a risk involved when leaving wood exposed to the elements. During the weathering process wood can appear unsightly as the material can blacken due to moisture getting into the fibres and pulling out tannins and extractives. Finish protects the wood from moisture absorption and UV degradation.

Installation & Advice

Deck Board Spans

21 x 145mm Yellow Balau decking should be installed with joists spaced at 400mm centres.  When installing the boards diagonally the joists should be spaced at 300mm centres.

Deck Board Spacing

Depending on the moisture content Yellow Balau deck boards can vary in width by +/- 10mm. Decking should be installed with a 5mm gap between the boards to allow for air circulation and expansion with changes to the humidity level. Before commencing installation please read Understanding how moisture causes dimensional changes in wood.


It is important to allow adequate air circulation underneath the deck to prevent cupping and warping of the boards.  It is recommended that a vapour barrier is used on the ground to prevent moisture from absorbing into the underside of the deck boards.


There are a number of different options available for fastening deck boards to the joists.  We recommend screwing through the face of every board using 5.0 x 60mm Countersunk Stainless Steel Screws. Fix two screws into every joist at quarter points on the deck board (36mm from each edge).  We recommend that pilot holes are drilled prior to inserting the screws.  This is particularly important at the ends of the boards to prevent splitting. 5.0 x 60mm Countersunk Stainless Steel Screws will flex slightly as the wood expands and contracts as the level of humidity changes with the changing of the seasons.

For a cleaner finish we suggest recessing the screws and using plugs to hide the screw heads.  Plugs can be cut from off-cuts of decking using a relatively inexpensive drill attachment called a plug cutter. 

Hardwood wrench

The longer the deck board the greater the tendency for it to be slightly bowed. To overcome this, most professional deck installers will carry a tool called a Hardwood Wrench, or Bow wrench, which enables the user to easily straighten a bowed board single handed as it is installed.  The Bow wrench is relatively inexpensive and can save a lot of time, so it’s worth buying even if you only use it for one project.  It can also he hired from some tool hire stores.

End Sealer

Yellow Balau decking from Silva Timber is end-sealed during the manufacturing process to help prevent splitting and checking on the ends of boards.  We recommend that if the boards are cut during installation then the exposed end grain should be sealed as soon as possible.   A clear, water-resistant wax such as Osmo Wax End Sealer should be used.

Cleaning and Maintenance 

Your Yellow Balau deck will benefit from regular cleaning.  Brush the deck with a stiff broom to remove dirt and dead leaves, and ensure that the gaps between the boards are clear of organic debris.  Clean the deck periodically with a wood cleanerto remove grime and mildew.  Yellow Balau decking can be pressure washed, but it is important to select a low setting to prevent the wood fibres on the surface from being damaged.

If your Yellow Balau deck is weathered it is possible to restore the natural colour with Wood Cleaner by Sansin®.  This product will remove weathering, mould, algae, mildew and iron stains and prepares the surface for recoating. 

If an existing finish or stain has broken down it can be removed using Paint and Stain Remover by Sansin®.  This product will remove most failed oil-based or latex finishes, extreme weathering, water stains, mould and mildew and restore wood to its natural colour.


Yellow Balau decking can be crosscut with a good quality chop saw using a tungsten carbide tipped blade.  Ripping can be done on a standard table saw, using a good quality, well-aligned fence and a tungsten carbide tipped blade.  When drilling, always use the highest quality drill bits available. If screwing through the face, use a countersink bit with a positive stop to ensure that all the screw heads end up at a consistent depth.  Screws can be lubricated to make installation easier.

Routing or planing can be done with high speed tungsten carbide cutters. The feed speed should be fairly slow. 


A dust mask and eye protection should always be worn when working with any wood.  Avoid the inhalation of wood dust.  We recommend a dust mask with an activated carbon filter. Some people may have an allergic reaction to hardwood dust.  Remove wood splinters immediately to prevent infection.


To ensure its quality, Yellow Balau decking from Silva is carefully manufactured, graded and inspected at source.  It is inspected again during the order picking process prior to despatch.  However, Yellow Balau decking is a natural wood product and is subject to variations in weight, density, colour, grain and performance. Yellow Balau decking is subject to dimensional changes as the moisture content in the wood fluctuates with humidity in the air. Swelling, shrinkage, checking, and other movement of individual pieces are normal occurrences in wood decking.


Yellow Balau Decking - Grade / Quality Information

Wood - A Totally Natural Material

Wood is a beautiful, natural and versatile material that cannot be replicated by any man-made product. It is the only building material that is naturally renewable and truly sustainable.

Wood is manufactured from trees which have developed naturally and responsively to their environment. Being a 100% natural product, it varies from one piece to another. Colour, grain and other natural features vary from piece to piece and within individual pieces.

Raw Material and Production

Silva's Yellow Balau decking is manufactured in Indonesia from the highest quality wood fibre. Rather than buying on an 'ad-hoc' basis from different suppliers with varying quality standards, we have been buying from a single reputable source for several years to ensure quality and consistency.


Silva's Yellow Balau decking is 'Standard & Better' grade which has excellent characteristics. Its appearance is almost entirely free of knots.

Inherent Attributes of Yellow Balau Decking

Being durable, hardwearing and attractive Yellow Balau is an ideal decking material and is a proven performer in the UK climate. This material has a few inherent attributes which are useful to understand to get the best out of it and ensure your project is a success.


The first thing to note about Yellow Balau is that it's not very yellow. It can have yellow-brown tones, varying to brown and dark reddish-brown. As with all wood species expect minor colour variance.

Sticker Shadow

At the point of manufacture deck boards are stacked in packs with thin slips of wood called 'stickers' between each layer to facilitate air flow around the boards. Sticker shadow is a result of the oxidation of naturally occurring chemicals within the wood causing a noticeable shadow mark across the width of the board. Sticker shadow is not unique to Yellow Balau, but it does seem to be more obvious on this species than others in our decking range.

Sticker shadow is an unavoidable natural occurrence and therefore not considered to be a defect. It can be easily removed by lightly sanding or left to weather out over time (usually 6 months or so) if leaving the boards unfinished.

To optimise dimensional stability, performance and appearance of the decking it is recommended that boards are coated on all sides prior to installation. An essential part of the coating process - regardless of the presence of sticker marks - is sanding with a random orbital hand sander using 60 grit paper. This provides a 'key' to the surface that enables the coating to penetrate into the wood. Sanding will also remove any other blemishes present on the face of the wood and will provide a cleaner and brighter surface upon which to apply the coating.

Pin Hole

Yellow Balau decking may contain a light scattering of tiny pin holes, which are caused by a small boring beetle in the living tree or freshly cut logs. The beetles cannot live in dried timber and the presence of pin holes is not indicative of active infestation. Pin holes are not detrimental to the structural qualities of the timber. This characteristic is accepted under the grading rules for this species and is not classed as a defect.

Surface Checking

Checks are small fissures in the surface of the wood normally occurring across or through the rings of annual growth and usually a result of the release of moisture (drying) on the surface.

Surface checks occur because of stresses that develop in the outer part of boards as they dry around the core that is swollen with moisture. They can also occur in resin ducts and mineral streaks.

Checks can appear in hot weather when the wood is exposed to the sun and the surface of the board dries at a faster rate than the core. They can also close and disappear as the wood absorbs moisture as the seasons change. Checking can be minimised by keeping the decking covered with a (breathable) tarpaulin and applying a coating to all sides of the board prior to installation.

End Checking

End checking occurs because moisture moves much faster through the end grain down the length of the board than through the face or edges of the board. Therefore, the ends of boards dry faster than the middle and stresses develop at the ends.

End checks can be minimised by sealing exposed or cut ends with end sealer.

Dust and minor surface blemishes

Dust and minor surface blemishes may be present - an unavoidable result of the manufacturing and handling process. Dust can simply be washed off. As with sticker shadow covered above, any minor blemishes on the surface can be dealt with by light sanding or will disappear over time if left to 'weather'.

Moisture Movement

Wood is a hygroscopic organic material that takes up and releases moisture according to the temperature and the relative humidity of the ambient air. As wood releases moisture it will shrink (usually during summer) and as it absorbs moisture (in the winter months) it will expand.

The rate of expansion and contraction will vary according to the grain orientation of the wood. This means that some pieces will expand or contract more than others, so there may be minor variances in the width of the boards (known as tangential shrinkage). Shrinkage in the thickness (radial) is minimal and length (longitudinal) virtually non-existent.


From our experience the characteristics covered above can occur or may be present on all Yellow Balau decking, regardless of the source. It's important to bear in mind that these characteristics are all superficial and what is more important is the quality of the wood fibre and production. To get maximum satisfaction and performance from your Yellow Balau decking, follow our recommendation to sand and apply a coating at the outset. You will be rewarded with a highly attractive and practical hardwood deck that will provide years of enjoyment and service.


The Timber Legality Assurance System (SVLK) assures the legality of timber products imported from Indonesia; in accordance with the Regulation No.995/2010 (Timber Regulation) adopted by the European Union in 2013.

The “Indonesian Legal Wood” certificate provides irrefutable proofs that timber products do not come from illegal sources. All Indonesian timber-related industrial units, primary or secondary will have a legality certificate and are audited independently the National Accreditation Body (Komite Akreditasi Nasional).

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