Q. I plan to install new flooring materials in my home. Can I just remove the carpeting and install my flooring material over the existing subfloor, or do I need an underlayment? I want my new floors to look as good as possible.
A. You are wise to think before you act. Most flooring failures or problems are traced to inadequate or poorly installed flooring underlayments.
All finished flooring, even carpeting, needs a solid foundation for it to perform well over time. All too often, builders and remodelers, as well as poorly trained installers, overlook the importance of floor underlayments.
For many years, wood-based products have dominated the flooring underlayment industry. Plywood, oriented strand board, sawdust composites, cement board, etc., are widely available and are commonly used in both new home construction and remodeling jobs. These wood-based underlayments can warp and swell when exposed to moisture. This can cause the finished flooring to buckle and fail even if the underlayment relaxes after it dries out.
Many consumers and tradespeople, unfortunately, make a wrong assumption about finished flooring, whether it be ceramic tile, hardwood, laminate flooring, etc. They feel that if the subfloor or underlayment looks and feels substantial, then it is fine to proceed with the finished flooring.
The truth is far more complicated. Many finished flooring products have specific recommendations for the type of material the finished flooring is placed upon. Even adhesive manufacturers consider the type of underlayment being used. For example, an adhesive may work well with the vinyl or ceramic tile, but that won’t matter if it bonds poorly to the underlayment.
A new underlayment product has recently hit the marketplace that is attractive to the flooring industry. Gypsum fiber panel is smooth, has superior water resistance, has higher impact resistance than traditional products, can be cut with a utility razor knife, is made with 95 percent recycled materials and is competitively priced.
Keep in mind that many traditional wood-based underlayments contain resins, adhesivesor dyes that can sometimes seep through and into the finished flooring material. If this happens, your finished flooring can be ruined. The new gypsum fiber underlayment doesn’t have these ingredients.
The new gypsum fiber product is available in two thicknesses: 1/4 and 3/8 inch, which allows you to create flush finish floor transitions when you change from one material to another. There is no reason why an angled transition threshold has to be used if you are installing finished flooring materials that are different thicknesses.
Many flooring problems happen in houses that are built over crawl spaces. Often an underlayment will buckle or warp because of water vapor that has escaped from the soil beneath the crawl space and then permeated the subfloor and underlayment. If you have a crawl space, be sure to cover the soil with a high-performance vapor barrier before you install any underlayment or finished flooring material.
It is also important to make sure that existing wood subfloors are dry before you install an underlayment. The moisture content of a wood subfloor should not exceed 15 percent. Use a moisture meter to test for moisture content. Be sure that the fasteners used to install the underlayment are driven correctly. The top of the fastener should be flush with the top of the underlayment or slightly below the surface.
Above all, make sure that you are using an approved underlayment. Get written specifications from the finished flooring manufacturer.
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Write to Tim Carter, c/o the Chicago Tribune, P.O. Box 36352, Cincinnati, OH 45236-0352. Questions will be answered only in the column. For a list of sources for gypsum fiber panels, underlayment comparison test results and other tips on installing underlayment, please send $3 to the above address. Ask for Builder Bulletin No. 401. Want to talk to Tim? Call him from 9 to 11 a.m. Central on Saturdays toll-free at 888-737-1450. Surf with Tim at www.askthebuilder.com.
