Sometimes a capping of concrete is installed over the sub-floor, to allow for the installation of tile, or radiant floor heating pipes. It is through this assembly that the forced air system ductwork will be installed, as well as miscellaneous plumbing and electrical lines.
There are three main types of floor structures, generally used in modern construction. These include framed, truss floors and manufactured joist systems.
Of all, the most commonly installed flooring system are framed floors. They consist of dimensioned lumber, bearing on exterior and interior load bearing walls or beams called “floor joists”. Generally the floor joists are installed, spaced 16″ apart. Installing rim and trimmer joists, to which the floor joists are nailed, finishes the perimeter. Bracing, usually in the form of bridging, but often installed as strapping, prevents the joists from turning in place. One other method used to prevent this type of turning is to glue the sub-flooring to the joists, as the sub-floor is placed. All joists must extend at least 1-1/2″ on to a bearing assembly, of either a beam or full height wall, unless metal hangers are installed to provide proper bearing support against other structural components. Beams, which support the floor joists over greater spans, are constructed in the form of laminated joists often referred to as built up beams, or one piece solid load bearing beams, cut from logs or manufactured. Electricians and plumber may often cut or drill into the joist work to install utilities, and this is accepted, so long as they do not remove more material than what is required by codes. This type of floor system is usually the cheapest to install.
Truss floors are simply that. They are constructed from small dimensioned lumber, interconnected in a webwork pattern by the use of metal or wood plates. Occasionally, the trusses will be built on site, utilizing plywood plates to connect the webwork together. Generally they are installed 24″ apart, either suspended on bearing walls or beams, or installed with plywood trim or rim joists around the perimeter. Strapping is installed on the bottom side, to prevent turning in place, which is a common ailment for deep truss components. In the case of long span truss work, bearing lengths of at least 3″ are quite common. Trusses span greater distances than framed floor assemblies and can be designed to span the entire building, eliminating center load bearing supports. They are moderately more expensive than framed floor assemblies, but provide a remarkably strong floor with little deflection or “bounce” to it. Another advantage to this type of structural system, is that utility installations can be run between the webwork components. Never allow trades to cut or drill into the members of a truss, for they are manufactured precisely for the loading conditions they will undergo during the life of the building.
The manufactured joist, which is a relatively new product, is often manufactured from low cost materials in the shape of an I beam, similar to steel beams in larger buildings. What this means is that the joist is constructed with a thicker top and bottom edge, and generally interlocking aspenite vertically spanning between the two. These systems are very strong, often capable of spanning the entire width of the building. One drawback is that this type of floor requires special hanger systems designed for the joists, to enable them to be hung from each other or against beams/bearing walls. Manufactured joists are becoming a popular flooring system, for they are relatively cheap, reduce labour time and provide adequate support. However, builders need to familiarize themselves with its installations, for poor installation can cause severe structural damage to the joists. A good example is a three point, center bearing joist, left with the top chord uncut, which can potentially fail or pull apart, over the center bearing point.
There are three main types of sub-flooring installed to cover and span the floor structure. It is over this that the finished floor will be placed. The sub-flooring types include raw sheathing, interlocking and strip. It is utilized not only to provide a surface for the interior finishes to be placed on, but also to prevent twisting or torque forces placed on the building. The sub-floor also allows load sharing within the joist framing system. Often the sub-flooring is glued to the joist work to eliminate creaking floors and to prevent the floor joists from turning.
Raw sheathing comes in 4’x8′ sheets, most often installed as 3/4″ thick plywood panels. This type of sheathing is adequate for spanning joist work spaced up to 24″ apart. The sheathing is lain with the joints staggered in such a matter, that no two edge joints line up with adjoining sheets. It is very easy to install, requiring the least amount of labour. The sheets are fastened with either 1-1/2″ flooring screws, or 2-1/2″ nails, spaced about 8″ apart. Although not required, it is a good idea to provide backers or supports under the joints, between sheets which run perpendicular to the framed floor assembly.
Most commonly installed are interlocking sheathing panels. This type of sheathing is generally 5/8″ thick, and manufactured as either plywood or aspenite (commonly referred to as “chipboard”) in 4′ x 8′ sheets. The sheets come with the long edges designed to interlock with a tongue on one edge, and a grove on the opposing edge. They are installed by simply pushing or pounding the sheets together, and nailing or screwing them to the joist work, in the same manner as raw sheathing. It is often the cheapest to install.
Strip floors, were once the most popular type of sub-floor installed. But with the introduction of manufactured sheathing products, it has become less utilized. Strip floors consist of 1″ by 6″ or 8″ boards, placed diagonally over the floor joist framing system. It is slightly more expensive to install, and requires experienced tradesmen. To install such floors properly, the lumber should be non-kiln dried, with a relatively high moisture content. This may seem odd, but in reality, as the wood dries out, it will shrink. This shrinking action pulls the floor together, adding strength to the overall system. The advantages of this type of sub-floor are its strength and durability. One important note, homeowners are often disturbed by the small 1/4″ wide gaps, generally left between the individual planks after the wood dries out. Although disturbing to see during construction, upon completion, the spaces are not noticeable, and really have no impact on the sub-floor components at all. Strip floors are designed to be interlocking, through lapping or spacing of joints.
Ah the finished floor, what we see and walk on everyday. For homeowners, this tends to be one of the more important aspects of the floor system. Yes the structure is a consideration, but the look and texture of the floor is what all that will be visible after construction is completed. The most common installed floor finishes include: vinyl sheet, vinyl tile, ceramic tile, wood strip, wood parquet, and carpet.
Most popularly used in bathrooms, kitchens, laundry areas and entryways are vinyl sheet, or linoleum floorings. This type of flooring cones in a vast array of colors, textures and patterns, in sheet sizes of 12 foot widths with varying lengths, and made from a vinyl composite, covered with a surface coating. It is installed by applying covering over the sub-floor, usually mahogany or particle core sheets 4’x4′ in size, to which the vinyl is glued to. It can also be installed directly onto concrete floors, in areas such as basements. Joining two sheets together is a standard practice when the room width exceeds 12′, or under doorways. Sheet vinyl is a good flooring in areas where water tends to accumulate, like around bathroom fixtures or at entry ways. It is fairly durable, and often maintenance free. Linoleum is one of the cheapest types of flooring to install.
Another good flooring for wet areas is the vinyl tile. Typically it is manufactured in much the same way as sheet vinyl, but is much more rigid and comes as 12″x12″ square units. They are installed in the much the same way, but require skilled tradesmen, familiar with proper installation. A good installer will start from the middle of the room to ensure that all cut tiles are equal in width at opposing walls. One advantage to this type of flooring, over sheet vinyl, is that it is can be installed, without danger of joint separation, over large areas. For this reason, it is often used in commercial buildings where large rooms are the norm. Vinyl tile can also be easily installed directly to concrete floors. Like vinyl sheets, it too is resistant to water, and tends to be installed in the areas of a building, prone to water accumulations. Tile, can be easily cleaned, is relatively maintenance free, and one of the cheaper finished floors to install.
Ceramic tile is probably the most durable types of flooring and is typically installed in entry areas, where sand scuffing and water accumulations are the norm. Bathrooms and kitchens often get this type of floor treatment as well, but due to the high cost of installation, homeowners tend to not include these areas. Ceramic tile are typically a square tile, although interlocking units are on the market, in standard square measurements of 4″, 6″,8″ or 12″. They are installed by one of two primary methods, either set into a thin mortar bed (called “thinset adhesive”), which also acts like glue, or a heavyset bed of 1-1/2″ normal mortar base. For all ceramic tile installations, the floor must be built up to ensure the strength required to prevent tile or joint cracking. Often, installers put down a material called “cement board”, which is much like drywall, but is made of glass fibers and cement. In any case, ensure that your installer will offer you a guarantee against future cracking or uplift of tiles. Ceramic tiles require little maintenance, but beware, water on glossy floor tiles can be very slippery, and many a time, a homeowner has resented the installation of a high gloss tile, over a bathroom floor area.
Wood strip flooring is one of the oldest types of flooring still popular in the modern age. It consists of wood strips, usually interlocking, which are either nailed or glued to the sub-floor. Often the strips will be prefinished, requiring no post applications of sealers or varnishes. This type of flooring is very labour intensive for installation, as well as being quite expensive to purchase. However, the results are a warm, durable floor surface, requiring little maintenance or upkeep. Wood strip flooring significantly adds to the strength of the support system, reducing the deflection (“bounce”) and gives the floor a very solid feel to it.
Of all the wood flooring, the most often installed is the parquet tile. They consist of square interlocking wood strips, held together with glues and/or metal wires. Often they come as single 6″x6″, or multiple 12″x12″ square tiles, about 1/4″ thick. They are glued directly to the sub-flooring, and are strong enough to span small deviations in it. The wood is often prefinished, and requires little maintenance. Parquet floors are a cheaper alternative to strip flooring, providing the same warm, durable surface.
Carpet is probably the most common floor covering that is used in residential homes. It comes in a wide variety of colors and textures. Carpet consists of woven fibers, which protrude upwards, glued or woven into a foam or jute backing. Often an underpad of pressed foam is installed below it or the backing can be integral with the carpet, adding to the softness and providing a much more comfortable surface for walking on. Carpet is installed by either gluing the carpet to the sub-floor, or the use of carpet tack around the perimeter. A good carpet will has a close weave, which will not show the backing material when separated. To reduce project costs, some contractors will opt to install a high quality underlay, with a low or medium quality carpet. This provides the soft surface, with equal durability, giving the homeowner the benefits of high quality carpet, at a reduced cost.