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Description
This pressure treated decking handrail and baserail profile is used to build traditional timber decking balustrades with vertical spindles. The same reversible 42 x 65mm rail can be installed groove-down as the top handrail or groove-up as the bottom baserail.
The matching infill, also known as a fillet, is cut into short spacers between the spindles. This keeps the spindles positioned consistently and gives the completed balustrade a neat, evenly spaced finish.
How many decking spindles do I need?
Measure the clear distance between the two posts after they have been installed. The calculator uses 41mm spindles and a design gap of no more than 99mm.
The finished gap is also the approximate length to cut each infill spacer. Measure every bay separately if the post spacing varies.
Approved Document K guidance says guarding in locations likely to be used by children under five should be arranged so that a 100mm-diameter sphere cannot pass through any opening. This is often informally called the “baby’s-head rule”. The calculator uses 99mm to avoid relying on a perfect 100mm site measurement.
How the handrail and baserail system works
- Cut the top and bottom rails to fit between your decking posts.
- Install the lower rail groove-up and the upper rail groove-down.
- Use the calculator to find the minimum number of 41mm spindles.
- Divide the remaining space evenly and cut the infill into matching spacers.
- Fix the spindles and spacers securely following the requirements of your balustrade design.
Product details
- Finished section: 42 x 65mm
- Length: 3.6m
- Profile: Reversible grooved handrail or baserail
- Material: Pressure treated softwood
- Use: External timber decking balustrades
- Compatible spindle: 41mm stop chamfer decking spindle
Installation and safety notes
The calculator only works out spindle quantity and spacing. It does not confirm that a complete balustrade is suitable for a particular drop, loading or location. Guarding height, post spacing, rail strength, fixings, climbability and the supporting deck structure must all be considered.
Timber dimensions and moisture content can vary slightly. Measure the actual opening and installed components before cutting every infill spacer. Treat all freshly cut ends with a suitable end-grain preservative and maintain the finished timber with an appropriate exterior coating.
