Foundation Type Selection
- Your foundation type should be chosen by this stage.
- For a standard foundation, your engineer will specify the foundation system, including concrete and reinforcement details.
- Specialized foundations, like piles or insulated foundations, will require contracting a specialist company whose engineer will provide the specifications.
Site Inspections and Reinforcement Ordering
- Your engineer will visit the site to verify that work is progressing according to plan.
- Building control inspection (NI) and certification from your certifier (which could be your engineer) are required at this stage.
- Concrete is typically ordered from a truck. If access is difficult, you may need to hire a pump or an extension to reach the site.
- Reinforcement, usually steel (known as rebar), can be sourced from a builder’s merchant.
Subfloor Installation and Plumbing Preparations
- Once the foundation is laid, follow your engineer’s specifications for the subfloor.
- Ground conditions may require additional reinforcement, such as bars or mesh.
- Before pouring the concrete slab, the groundsman must install piping for kitchen and bathroom waste, extractor hob ventilation (if needed), and waste pipes for appliances like washing machines.
- Confirm plumbing and electrical plans with the plumber and electrician.
Radon Sump and Service Installations
- The groundworks contractor should install a radon sump if required, and an external air supply if you plan to use a stove or combustion appliance.
- Check if an additional outlet is needed for the hob extractor, depending on your chosen model.
- Services might be installed in the screed, but this depends on the depth; ensure all services are accounted for.
- If pipes require cutting through the radon barrier, it will need to be resealed using proprietary clips, ‘top hats,’ and an approved adhesive system.
Drying Time for Wet Pours
- Wet pours, whether for slab or screed, will need drying time depending on type and thickness.
- Verify the drying duration in advance, and monitor moisture levels using a meter after pouring.
- It is recommended to avoid painting or applying undercoats until both the floor and plaster are dry. This can take one day per mm of thickness with cross-ventilation but depends on specific conditions.
Tiling Preparation
- Before tiling, the underfloor heating must be gradually heated to commission the screed.
- Some additives can reduce drying times, but for tiling on anhydrite screeds, the surface must be primed with a calcium sulphate screed-compatible primer as per the tile adhesive manufacturer’s instructions.