Flooring Design Requirements in Buildings

The basement in many buildings is a cast-in-place concrete slab with limited design considerations for structural support or environmental control. However, the basement may be a more complex system consisting of waterproofing and wear plates and a layered, structural base plate. This system is designed to withstand hydro static pressure and provide a controlled environment.

The main problem in floors is leakage, as concrete is the most common material and cracks are a common problem in concrete elements. Another concern when designing floor plates is controlling soil gas emissions like radon. The design and construction of floor plates is key to expected performance, durability and longevity. Also, repair of a foundation slab can be quite expensive or practically impossible once it is complete.

When designing flooring, the best approach is to be very conservative, especially in areas to be buried. It is recommended to combine high quality materials with additional reinforcements to reduce the risk of failure.

Structural Support

The base plates of a low grade building enclosure must withstand vertical gravitational loads and upward soil or hydro static pressure loads. Downward loads come from the dead weight of the floor slab and loads loaded in occupancy such as pedestrian traffic. In some structures, the floor slab can also serve as a matte foundation slab that resists significant loads from pillars and walls.

Depending on the location and the water table of the region, the floor plates can also be exposed to upward soil and hydro static pressure loads. Upward soil pressures can be applied to the floor slab when a mat is designed as a foundation, while building point loads are downward forces.

Environmental Control

It exposes the outdoor foundations to thermal effects, moisture, insects and soil gas. Thermal effects and air humidity in particular can also come from indoor sources. As with other elements below the class, the performance of a floor slab will depend significantly on its ability to withstand and regulate these environmental influences. Prevention of cracks is crucial for both structural performance and leakage prevention.

Humidity control measures usually include a drainage and barrier type system. In cases where there is hydro static pressure from groundwater, the first moisture control component is a pumping and dewatering system to mechanically move the water table downward. The second component of the moisture control system includes a granular layer of aggregate under the floor slab that provides an area for moisture to accumulate and dissipate. Moisture can also be pumped or discharged into a sump system or outlet drain. In areas with low water table or dry conditions, the granular aggregate layer and outlet drain are normally sufficient for moisture control.

Once the moisture control system has been defined, the next step is whether to include a waterproof membrane or vapor retarder under the floor slab.

A vapor retarder acts as a barrier against vapor migration without hydrostatic pressure.

Waterproofing membranes will provide resistance to both vapor migration and hydrostatic pressure.

Most building codes require a vapor retarder as minimal protection against moisture, even in areas with low water tables. Vapor retardants also minimize shrinkage stresses and cracking in the floor covering. Waterproofing membranes are required indoors that are sensitive to hydrostatic pressure and humidity. These membranes are usually applied to a granular aggregate or a mud slab poured over a layer of compacted soil.

Soil gas is another environmental situation. The migration of soil gases such as radon can be controlled with a polyethylene-type vapor retardant or waterproofing membrane. Protecting the membrane during construction is important in terms of attention to detail in all terminations, edges and penetrations. This provides uniform control over moisture or soil gases.

Flooring and MEP Distribution Systems

When dealing with floor systems, interior lining alone is a concern. The requirements for this coating depend on the use of the interior, and some common coverings are carpet, tile and bonded floors. When using tiles or any bonded floor, steam control is essential to ensure proper adhesion. In parking areas or storage areas, the interior lining may be the exposed surface of the concrete floor.

The floor plate may include components of MEP installations such as mechanical piping, plumbing lines, and electrical feeders. These elements should be designed to withstand the expected loads acting on the floor slab when present. MEP distribution systems should also be designed for ease of maintenance or modification.