We walk on it every day at home, and yet, we pay little attention to the floor layers beneath our feet. The fact is that there is more to the layers of flooring in a house than meets the eye. It’s something that is extremely flexible when it comes to changing the look of a house. The support structure of the floor exists underneath, with a sub floor built on joists on which the top layer of the floor that is visible is laid to create a stronger and more durable structure.
The advantage of well-installed floor layers is that it makes it easy to change just the layer at the top to refresh the look of an area. It’s the joists underneath that take care of the functional aspects of bearing the load, so even a light material can be used for the top layer, so long as it meets the specifications required to survive the foot traffic in the area without wearing out quickly.
What are the different floor layers, and how many layers are recommended by architects? In this article, we outline the various flooring layers, their purpose and the materials that are ideal for each one. Additionally, we provide information on how to install subfloor over existing flooring.
The top layer or the floor finish is what we see. It’s the easiest to replace as it is installed on the structural support underneath. The idea behind the top floor is to decorate the room, just as we use rugs or bed covers to improve the aesthetics of an area. While it offers protection to the subfloor layers, its main function is decoration. When the top floor layer is removed, one usually sees a substrate or an underlayment below it.
What we refer to as a floor is, in fact, a mere covering over the subfloor. The materials most commonly used for the top floor layers are ceramic tiles, natural stone, wood, laminate, vinyl and carpeting, among others.
While there are several floor layers below the top layer, the underlayment is the one that is immediately below it. It might not exist under every floor covering as its an optional layer used to smoothen the surface to make it easier to install the finish layer. The type of material used for the top layer determines the material for the underlayment.
For hardwood or engineered wood floors, covering the subfloor with plywood is the usual practice. For ceramic tiles and natural stone, which require the application of cement, a cement backer board will be used as the underlayment. As for laminate flooring, they require a completely different approach. The underlayment comprises a thin layer of foam that is rolled out over the subfloor and taped in place to smoothen the surface before the top layer is installed.
The subfloor is the level just below the joists. It’s the strong layer on which the underlayment and the top floor finish can rest. It needs to be strong enough to bear the weight of everything in the house that rests on the floor, whether it’s the people walking on the floor or the furniture resting on it. Since it is a structural component of the flooring, it needs to be strong. Among the subfloor materials commonly used for houses are OSB (oriented strand board) or plywood. Subfloor plywood boards need to be thick (between 19/32 inches to 1 & 1/8 inches) so that they can provide the required support. In terms of providing structural support, only the joists trump the subfloor.
In some homes, one comes across concrete slabs used for the flooring. These are usually considered a subfloor.
Joists refer to a matrix of structural support created using engineered wood, laminated wood or other timber. Although they aren’t really a layer of the floor, joists are an essential component of floor layers as they create the support grid on which the entire flooring is installed. Not every type of floor requires joists. For example, a concrete slab floor can be laid without joists.
The number of layers depends on the material that is used for the flooring as well as the condition of the existing floor, in the case of replacement. Usually, a concrete floor will have just a single layer. In some homes, one might find a solid wood floor that is fixed on the joists without using a subfloor or an underlayment. Sometimes, an underlayment might not be required if the sub layer underneath is smooth, allowing the finish covering to be installed directly on it.
While the four layers mentioned above are the standard in most houses that use hardwood or engineered wood on the floor, in older homes that have undergone several remodelling projects, one often sees multiple floor layers. In most cases, the reason for this is not to provide additional support, but rather because some homeowners avoid stripping the layers underneath as it adds to the labour cost of the renovation.
The thickness of each layer can contribute to the sturdiness of the floor structure. However, the recommended thickness of each of the layers is also dependent on the type of material used as well as the load that the floor is expected to bear. For instance, in a kitchen, the floor layers should be completely flat, firm and inflexible as it needs to be strong so that it can hold heavy appliances such as refrigerators, cooking ranges and dishwashers. Therefore, ceramic tiles or natural stone are preferable to wood for the floor covering.
Certain parts of the flooring, such as the area with a heating vent, the cross-section at the top of the stairs or the interiors of closets give a fair idea of the thickness of the existing floor layers as they are at a different level from the rest of the floor. By using a measuring tape, one can get an idea of the thickness of the layers as well as identify the number of layers under the top covering. This can help to decide whether it’s necessary to strip all the layers or just a few before installing a fresh finish at the top.
While the measurements can be done by homeowners, we recommend consulting a professional architect before taking any decision regarding the removal or installation of floor layers. Since they have experience in renovating and installing floors, architects can advise whether the floor material is ideal for the load of the area and if any of the layers need to be strengthened to make it sturdier. Additionally, they can provide guidance on the ideal materials and the thickness of the subfloor layers as well as the best way to create strong support that allows the top layer to be refreshed without having to replace the rest of the layers every time a renovation is needed.