Decking spindles are the vertical balusters fitted between the handrail and base rail on a raised deck. They form the infill of a balustrade, preventing falls from the edge of the deck while giving the structure a finished, attractive appearance. They are a safety requirement on any deck raised enough to pose a fall risk.
Decking Spindles and Balustrade Components for Garden Decks
Decking spindles are the vertical balusters that sit between the handrail and base rail on a raised deck, completing the balustrade and preventing falls. MacBlair stocks pressure-treated timber spindles in a range of profiles to suit different decking styles. Available options include:
- Square spindles: clean lines that work with both contemporary and traditional decks
- Stop chamfered spindles: a classic detail with angled cuts near the top and bottom
- Turned spindles: a more decorative profile suited to period or cottage-style outdoor spaces
All spindles in the range are pre-treated with preservative to resist rot, moisture, and insect attack, which matters in the Northern Irish climate. The treatment gives the timber a characteristic green tint. If a consistent colour finish is a priority, apply a Decking Stain after installation. Standard sizing is 41 x 41mm at 900mm height, fitting most balustrade systems including both traditional and universal rail profiles. Spindles should always be fixed using pilot holes to avoid splitting the softwood.
Raised decks in the UK fall under Building Regulations Part K, which sets requirements for balustrade height and maximum gaps between spindles. A general rule of thumb is one spindle approximately every 110mm, creating a gap too narrow for a child's head to pass through. Pairing spindles with the correct Decking Handrail and Decking Baserail keeps the whole balustrade structurally sound and compliant. Decking Posts anchor the system to the frame and should be fixed to joists with coach screws or bolts before rails and spindles are fitted.
While pressure treatment provides a solid foundation, it does not make timber fully waterproof. Finishing with a Wood Preservative Treatment or decking stain after installation adds a further layer of protection and extends the life of the balustrade. Browse the full Decking range at MacBlair for boards, fixings, and all the components needed to complete a deck from the ground up.
Decking Spindles FAQ's
The most common size is 41 x 41mm at 900mm in length. This fits the majority of standard balustrade rail systems. Some applications use taller spindles at 1100mm, typically where a taller overall balustrade height is needed. Always check the rail system you are using to confirm compatibility before ordering.
A widely used guideline is to space spindles no more than 100mm apart, leaving a gap that a 100mm sphere cannot pass through. This is the benchmark referenced in UK Building Regulations Part K for preventing a child from getting their head trapped. In practice, placing one spindle approximately every 110mm centre-to-centre achieves this safely. Always check current building regulations for your specific project before finalising spacing.
Yes. Because spindles are used outdoors and exposed to rain, frost, and humidity, they should be pressure-treated with preservative to resist rot, decay, and insect damage. Most spindles sold for decking use are pre-treated, which gives the timber a green tint. Pressure treatment protects the timber internally, but it does not make it fully waterproof. Applying a decking stain or wood preservative on top after installation adds an extra layer of protection and extends the service life considerably.
Yes, timber decking spindles can be trimmed down with standard hand or power saws if a shorter length is needed. Bear in mind that cutting through the treated outer layer exposes untreated timber at the cut end. It is worth applying a cut-end preservative or end-grain sealer to any cut surfaces before installation to maintain protection against moisture and rot.