Double flooring is a type of construction where the floor is created using a series of binding joists that allow for the addition of flooring joists on one side of the floor surface and a second set of ceiling joints on the opposing side. This type of double floor is common in many residential dwellings that involve two or more stories. There are several advantages to using this particular design strategy, as well as a couple of potential drawbacks that should be considered.
One of the main advantages of a double floor is the stability that the design provides for the overall structure. The placement of joists to create a ceiling above and a floor below helps to secure the walls of the building in a unified pattern that decreases the potential for instability as the walls extend upward. This added stability to the walls is also important in terms of providing support for the roof.
Along with strengthening the building in general, a double floor also offers the practical advantage of reducing the amount of sound that passes from one story to the next. When a double floor is infused with insulation between the joists, this makes it possible for people on one floor to be listening to music or having a party while preventing the noise from disturbing people who are on the other floor. In many residences where the bedrooms are located on the second floor, this design is particularly practical.
While there are advantages to using a double floor design, there are also potential disadvantages to consider. The series of joists above and below do add considerable weight to the floor that must be supported by the binding joists that are found along the wall. Another important consideration is the height that this floor design adds to the overall structure. While this additional height in and of itself is minimal, even that small amount can make a significant difference in the materials needed to provide the extra support and the finishing on both sides of the floor. This in turn can increase the cost of constructing the building considerably, a factor that may be very important if the building is being done on a tight budget.
If the desire is to make use of a double floor as part of the construction, care should be taken in placing the binding joists that will bear the weight of the floor. This means taking into consideration any openings in the walls, such as doors and windows, and strategically placing those binding joists so they are attached at the stronger points along the wall line and not the weaker areas. Doing so will help distribute the weight of the double floor more equitably without placing stress on the weaker points, and possibly causing the structure to be more susceptible to cracking or some other type of structural failure.