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Plan the Stair Layout
Before any timber stakes are cut, confirm the total rise, the number of steps required and the space available. Residential stair dimensions must follow the National Construction Code (NCC), which sets expectations for riser height, going depth and consistency across all steps. Because councils often refer builders directly back to the NCC, it’s worth checking that your measurements fall within accepted ranges.
Mark a clear reference line for the stair flight, confirm levels with a spirit or laser level, and ensure the ground is stable enough to support formwork and fresh concrete.
Choose Formwork Materials
Formply is the preferred material for stair risers and sides due to its smooth face and durability. It helps produce clean edges and reduces the likelihood of bulging. Timber stakes, props and screws suited to outdoor conditions are typically used to secure the formwork. Reinforcement mesh or steel bars will usually be required, but exact specifications depend on the stair size and load requirements.
If the staircase will exceed a few risers, expect to invest more time in bracing. Taller stair flights place greater pressure on each riser, and insufficient support is one of the most common causes of blowouts.
Build and Brace the Formwork
Once the layout is confirmed, cut the formply to suit each riser and secure it firmly in place. Ensure every tread and riser matches your calculated dimensions. Even minor variations can lead to uncomfortable steps or non-compliant work.
Bracing must prevent any movement during the pour. This includes bracing along the stair sides and supporting each riser so it cannot bow under pressure. Joints should be tight to minimise slurry leaks, and reinforcement must be tied securely so it stays in position when the concrete is vibrated.
Prepare for the Pour
Before placing concrete, check:
- All risers and treads are level and consistent.
- Formwork is firmly braced.
- Reinforcement has the correct cover.
- Joints are sealed and gaps closed.
Small issues at this stage become major problems once the concrete is placed.
Pouring and Finishing
Concrete should be placed steadily to avoid overloading any riser. A concrete vibrator helps remove trapped air and improves durability. Finish each tread with the desired texture, especially for external stairs where slip resistance matters.
Allow the stairs to set before removing the formwork. Full curing takes longer than the initial set time, and removing boards too early can damage the surface or weaken the edges.
Avoidable Mistakes
Most problems with concrete stairs come from setup issues rather than the concrete itself. Common errors include:
- Riser movement caused by insufficient bracing.
- Inconsistent step heights due to incorrect marking.
- Slurry leakage from poorly sealed joints.
- Reinforcement shifting during the pour.
- Removing formwork too early.
When to Get Help
Complex layouts, taller stair flights or architectural designs such as floating or cantilevered steps require more advanced formwork and reinforcement planning. If your project falls into these categories, or you’re unsure about compliance, it’s best to speak with a specialist.
Form Direct supplies formwork materials, tools and accessories suited for stair construction. If you need guidance selecting products or want support for a more involved stair design, our team can help you choose the right solution for your project.
