Interior Floors

Squeaky or uneven floors, gaps between flooring materials, excessive bowing or deflection — no matter what the floor finish, remodelers and builders do themselves and their clients a favor by ensuring that the substrate is in proper condition before th...

August 31, 2001

This month we will look at how the Residential Construction Performance Guidelines address interior floors.

Squeaky or uneven floors, gaps between flooring materials, excessive bowing or deflection — no matter what the floor finish, remodelers and builders do themselves and their clients a favor by ensuring that the substrate is in proper condition before the installation of that final surface. Naturally, this is easier during new construction, but remodelers should take advantage of any occasion to bring those areas within tolerance.

Remodelers’ clients often request installation of a new floor finish, particularly on kitchen and bath projects. Any switch to a new flooring material needs to be preceded by careful consideration of the weight as well as the compatibility of the new surface with the substrate. One example is the placement of new surfaces over OSB. This may not be the suggested surface for adhering strip hardwood flooring because of the difficulty the staples have gripping the wood. Moisture introduced from certain water-based mastics could also influence the surface. If adding an additional underlayment is the solution, it is essential that remodelers factor the change of floor heights to door thresholds, cabinet and vanity heights, and transitions into other rooms. Obviously, when the old surface is removed, this is an excellent time to detect and remedy any floor areas that squeak or are uneven.

The increasing popularity of finishes such as Mexican tile presents additional challenges. Without adequate support from the floor joist, the floor will be subject to cracks and gaps because of potential movement. Remodelers upgrading to tile for their clients should ensure that the structure will support the considerable added weight of the tile and grout bed. Most of this information for structural requirements is available through the supplier or trade association under installation specifications.

Finally, certain floor fillers are acceptable to remove slight variations in the levelness of the surface. Generally, these are
acceptable to a great many applications. As always, read the

In summary, before installing new floor finishes: Check tolerances as you go to make sure they have been met, and make sure the substrates are compatible with the new surfaces.

Characteristics of Floor Finishes

Hardwood Floors: The Guidelines address several aspects of hardwood flooring installation. Gaps between the wood strips, for example, should not exceed 1/8 inch at time of installation. These will naturally grow depending on the climatic conditions and the relative humidity during occupancy of the dwelling. Therefore, the tolerance is measured at time of installation. Cupping, also influenced by the degree of humidity, is controlled by a tolerance of 1/16 inch in height in a specified span but is not a remodeler or builder responsibility if the area is exposed to
excessive moisture.

Guideline 10-16 defines the concept of acceptable degree of lippage between materials — that is, where two adjacent strips of wood meet and one is higher than the other. This should not exceed 1/16 inch. To determine if the installation meets this guideline, place a quarter on edge. If the higher strip is above the height of the coin, the lippage is excessive.

Tile Surfaces: Excessive lippage is also a consideration in tile, stone and marble installations (Section 10-26). Tolerances here are defined as the same as for the wood application, and the "quarter rule" works just as effectively. These installations also involve application of grout, with the potential of variation for color and texture. Use the standard "6-foot rule" for visual acceptability of these variations (Section 10-27). The stone, tile or marble itself should not break or become loose, necessitating replacement of certain areas. Most important, as discussed earlier, the condition of the subfloor has a profound effect on the performance of the finished floor and thus should be the focus of attention at earlier stages of the project (Section 10-24).

Resilient Flooring: When new vinyl flooring products are installed, it should be noted that gaps in sections of flooring, which are inevitable in some cases, are generally sealed with a seam sealer (Section 10-8). The client should be reminded that even new installations that require a seam are addressed in the same manner. Unfortunately, resilient flooring is not resistant to nail pops from the subsurface. Again, the importance of the proper nailing of the underlayment cannot be stressed enough. If the nail pops are readily visible, the remodeler or builder has the option of repairing or replacing the flooring, with the likelihood that the pattern or color dye lot might not match. The popularity of "screwing and gluing" the subfloor to the joist for all finish surfaces has increased primarily because this method virtually eliminates edge movement of the wood. Consider the extra cost as buying insurance on the front end of the project.

Carpeting: The Guidelines point to the unacceptability of gaps in carpeting seams, although a seam may be visible. This distinction should clearly be made with clients (Section 10-1). The remodeler faces ambiguity in situations where the carpeting run intersects at a 90-degree angle; for example, at the intersection of a hallway and a bedroom. The client may diagnose an unacceptable installation when the difference is simply the direction of the nap of the carpeting. This can often be a result of the grade of carpeting chosen for the installation. An additional assistance to the client in the selection of the carpet is for the vendor to demonstrate the performance of a sample on the quarter turn that would be visible in the hallway intersection. Here, as with all aspects of interior floor finishes, early prevention is far better than cure.

Bob Merz of Construction Arbitration Associates Ltd. in Roswell, Ga., heads the Work Group for the Residential
Construction Performance Guidelines.

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