How to Properly Install Waffle Slab Formwork.
Waffle slabs are a popular choice for building construction due to their excellent strength-to-weight ratio and ability to support large spans. However, proper installation of the formwork is crucial to ensure the slab’s structural integrity and longevity. Here are some guidelines for installing waffle slab formwork:
1. Set up and prepare the site.
Before starting, clear the site of debris and make sure the area is level. Determine the height of the slab and mark it on the walls of the building or use string lines to create a level guide for the formwork. Install the perimeter formwork, such as timber battens, to the correct height to create the edge of the slab.
2. Place the polystyrene pods.
Polystyrene pods are placed on top of the formwork to create the voids or ‘waffles’ in the slab. They come in different sizes and spacing, depending on the span and load requirements of the slab. Align the pods to the markings on the perimeter formwork and ensure they are securely in place. The pods should be about 50mm below the top of the perimeter formwork.
3. Install reinforcement.
The reinforcement for the slab is then installed, consisting of steel mesh and bars. The mesh is laid over the polystyrene pods and cut to size, ensuring a 50mm overlap at the joints. The bars are placed on top of the mesh and tied together with wire or clips. It’s important to ensure adequate cover to the reinforcement, which is typically 30mm, to protect against corrosion and ensure appropriate bonding between the concrete and steel.
4. Install more formwork.
Temporary formwork is installed at the top of the polystyrene pods, creating the ‘top form’ of the slab. The top form should be rigid and strong to support the weight of the concrete. Plywood or steel sheets are commonly used for this purpose. The formwork should be level and securely fastened to the perimeter formwork so that it can hold the weight of the wet concrete.
5. Pour and finish the concrete.
After the installation of formwork and reinforcement is complete, wet concrete is poured into the formwork. The concrete should be evenly distributed to avoid air pockets or voids. To ensure proper consolidation of the concrete, use a vibrating screed or trowel on the surface. The concrete should be finished to the correct level and smoothness, to ensure adequate drainage and ease of cleaning, if necessary.
6. Remove the formwork.
After the concrete has cured, the formwork can be removed. Carefully remove the top form, ensuring that the polystyrene pods are not damaged or dislodged. Remove the perimeter formwork and clean the edge of the slab. Any excess material should be removed, and the surface can be finished as desired.
In conclusion, proper installation of waffle slab formwork is critical to ensure its strength and durability. It’s important to follow the guidelines mentioned above and pay attention to the details, such as reinforcement cover and formwork fastening. By doing so, the waffle slab can provide many years of reliable service while being a cost-effective solution for building construction needs.
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