Deck finishes Overview

Deck finishes need to consider both the functional use, and also the aesthetic appearance, as seen from inside the apartment. Especially when it’s raining, the functional performance is paramount. Consideration must include how the finishes will perform in heavy rainfall, slip resistance, maintenance and durability.

Whether hardwood, softwood, or composite, Grooved decking boards are commonly used as a balcony surface finish. Experience has shown that the majority of rainwater falling on a decking board will run along the grooves and drip off the end of the board. For this reason it is generally better to run decking parallel with the building line, otherwise there can be a substantial amount of water dripping of adjacent to the façade, giving an increased risk of staining or water penetration.

There are many other finishes available from tiles and paving, to artificial grass. For many of these applications, the best solution is often to use a closed Cassette® balcony to provide a solid top surface, to which finishes can be applied. This will usually offer the benefit, of avoiding the need for waterproof membranes, etc. which would be required when applying finishes to most concrete balconies.

Composite decking has become the most popular choice for most balconies, as the longevity, low maintenance, and high perceived value are considered. Most composite decking products use a hidden clip captivated within the gaps between boards. This not only provides a very neat finish, but also makes, manufacture, replacement and maintenance much easier.


Level Threshold

Part M guidance, British standard, NHBC and Lifetime homes guidance all look for buildings to be designed with door sills which allow less able, or wheel chair users to easily access balconies. NHBC guidance, for example, states that “door sills must project a minimum of 45mm along with a maximum upstand of 15mm at the door threshold. “ This is to allow minimal obstruction. Synergistical consideration is needed for deck finishes heights, internal finishes and fenestration. The substrate to which the balcony connection is fixed are typically finished with insulation, floor screeds, etc. along with final finishes, which raise the FFL above the height of the arm. Cassette® balconies have therefore been designed so that

the balcony sits at approximately the right height, with the specialist stirrup clamp enabling minor site adjustment to be made. This can sometimes avoid the need to have a stub with a staggered joint from an anchor (as typical with bolt-on balconies). Staggered joints increase the moment, thus making the balconies deflect more and feel bouncy. A few door sill interface examples can be seen in the door sill interface section.

NHBC Decking guidance

The NHBC guidance in relation to decking and paving layout and spacing, was commonly considered as difficult to understand and could be interpreted various different ways. This confusing has generally been addressed by the new NHBC guidance, which clarifies decking gap restriction in three parts:

  • Gaps should be provided between decking and paving at balcony perimeters.
  • Minimum 10mm gaps should be provided between individual units of decking or paving, and the threshold sill, perimeter walls, and kerbs.
  • Spacers and supports which raise decking or paving should not obstruct the flow of rainwater to outlets.

Further threshold and door sill interface detail can be viewed here.



Natural timbers, and some composites, are fixed using screws. This can look messy unless using hidden screws, either way both make initial fixing and maintenance much more tricky. Our preference is to use hidden decking clips which enable fast install, and easier removal of individual boards.

Sapphire can also offer a solid aluminium surface with drainage holes to enable finishes such as paving, astroturf, etc. to be installed afterwards.

By far the most common deck finish for balconies is decking. Decking can offer a practical, cost effective and durable solution if specified correctly.

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