What is important in flooring construction?
In our previous articles we discussed the uses of materials such as timber and masonry in construction. Now we’re going to talk about floors, and what is important in constructing them, including materials.
What is a floor?
Let’s confirm what a floor is so everyone knows what we’re dealing with. A floor is a hard structural component used to create horizontal storeys. This could be the ground floor, or floors above this, and is a room’s base.
They can be made from wood, or from a stone or concrete slab when it’s a ground floor.
The important thing about floor assembly is that is needs to hold the weight of the inhabitants, as well as the weight of the furniture, and its own weight. The floor shouldn’t sag, so supports are needed that are spaced in certain intervals.
Functional needs of floor construction
There are different functional requirements of typical floors in a building. They include:
Strength and stability
The quality of the materials used to build the floor determine its strength.
The stiffness of the floor should be enough to keep it stable and level under not just its own weight but that of the furniture and people in the room. The floor also needs to support water, electrical, heating and ventilation systems without affecting their stability.
For small homes, concrete without reinforcement might be enough, whereas a reinforced concrete slab is needed for heavier loads like machinery. Also, if nearby deep-rooted trees are present, suspension-reinforced concrete slabs are needed.
Resistance to weather and ground moisture.
In the ground floor of a building, especially a heated building, rising ground moisture will make the floor slightly damp and chilly. Additional heating is needed in this case.
The type of subsoil, water table and if the ground is flat or not can also influence the moisture penetration level from the ground to the floor.
The diagram above shows how this happens.
Durability and maintenance free
Water-tight ground floors on strong foundations, and suspended floors supported by walls and roofs generally should need only minimal upkeep. The materials used and the wear they get will contribute to the durability.
Floors need to survive a fire for long enough for any occupants to escape. Based on the thickness of the concrete cover, the British Standard 476 (BS476) and ACI 216.1-7 (Code Standards for Assessing Fire Resistance of Concrete and Masonry Building Assemblies) determine fire resistance ratings that range from one hour to four hours.
Finally, compared to timber floors, reinforced concrete floors can withstand fire for a longer amount of time.
Resistance to passage of heat
When there are significant air temperature differences in the opposite sides of the floor, the floor needs to resist the release of heat. For example, insulation is needed when an open port vehicle is built beneath buildings and the floors above the port are exposed to the elements.
By using concrete and a damp-proof membrane, the ground floor can be built in a way that inhibits heat transfer from the ground to the floor or from the floor to the ground.
The damp-proof membrane will prevent floor damping and a cold sensation by being positioned on, under, or sandwiched in the concrete beneath the floor. This will result in a fall in heat transfer and the heat that is required to maintain a pleasant environment.
Applying a layer of heat insulation around the perimeter and below the floor slab is essential if under floor heating is used to minimise heat transfer to the ground.
The diagram shows a typical building’s heat loss through the floors.
Heat loss through suspended floors.
It is likely that the suspended floors within a framed building will be at an intermediate level, and the area beneath it will be within the interior of the building.
Heat transfer is unlikely to be a major factor unless the floor separates areas that are heated from those that are not. This may be the case where the basement area is used for parking, for example. In such instances the void will be subject to the passage of air, and the creation of a steady state central area as seen in solid floors will not be possible. It may be essential to provide a uniform level of insulation across the whole of the floor.
Resistance to passage of sound
The fact that upper floors act as a sound barrier and inhibit sound transmission between residences is extremely important. Compared to low mass timber floors, reinforced concrete floors are more effective at blocking the transmission of airborne sound. Because of this, a reinforced concrete floor can be used to effectively divide residents. Also, to increase the sound resistance of wood flooring, areas between timber joists can be filled with thick substance or light-weight insulation.
Provision of appropriate surface finish:
Ground floors must provide a level and smooth surface even though it is quite probable that they will not receive decorative finishes in many cases.
In the case of industrial buildings floors are generally left with a concrete or screed finish which may be sealed or primed to prevent contamination and surface damage from spillages etc. It is unlikely that they will receive any form of decorative surface finish or carpeting for example.
In the case of commercial buildings, it is increasingly common for raised access floors to be provided; the surface of the structural floor is unlikely to be exposed to direct contact with the users of the building. If this is the case it is still essential that the finish is level and true, since minor undulations and irregularities can result in problems with installation of
the raised floor.
Unlike floors to homes, concrete floors to commercial and industrial buildings are often provided with a power floated surface.
It is normally the case that the cheapest option that allows the floor to perform its desired function will be adopted. Hence the minimum possible standard of surface finish to the structural floor will be chosen. It is not always necessary or appropriate to finish the floor surface to high levels of tolerance.
Keep an eye out for more exciting articles on other construction considerations in the building industry. In the meantime, if you want to learn more about flooring construction, check out this article.
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