Finishing Exposure 1 OSB Sheathing

TECHNICAL NOTE Finishing Exposure 1 OSB Sheathing

Number N300B Finishing – Interior Applications ing this look. However, absorption of oil-based semitransparent stains can be April 2001 The choice of interior finishes for OSB inhibited by wax, resulting in a washed- sheathing panels in dry use areas is gener- out appearance. If wax is present on the Introduction ally dependent on the desired aesthetic surface, a water-thinned semitransparent effect and whether wax is present on the Oriented Strand Board (OSB) sheathing stain may be preferable. If in doubt, panel’s surfaces. Some manufacturers may be used in interior applications for consult your distributor or try the finish incorporate wax into the panel’s surfaces decorative purposes. It is often desirable on a representative sample to determine to improve resistance to moisture pene- to finish these panels to enhance their what the final appearance will be. tration. The quantity of wax varies from appearance and protect them from one manufacturer to another. If the panel Solid-Color Stains and Paints. These normal wear and tear. surface is waxy, it can affect finish perfor- finishes are opaque and provide a uniform OSB sheathing panels rated as Exposure 1 mance. Some of the more popular interior color to the panel, but still allow the are designed for applications where long finishes, along with considerations relative surface texture to show. Water-thinned construction delays may occur or where to surface wax, are described below. solid-color stains are preferred over oil- high moisture conditions may be encoun- based formulations, since solvents in oil- Clear Finishes. Clear finishes can be used tered during their service life. Although based solid-color stains can dissolve wax on OSB sheathing for indoor applications they are not intended for permanent and result in bleed-through and a mottled to show off the natural wood color and direct exposure to weather, they may be discoloration. Best results will be achieved highlight textures. Two coats of a clear used for certain applications such as open by application of a stain-blocking primer penetrating sealer provide the most nat- soffits where they are only exposed on the compatible with the topcoat. ural appearance. These types of finishes underside. OSB sheathing used in this help protect the wood from soiling and Paints are available in a full range of type of application should be finished to improve moisture resistance. If a clear gloss levels, including flat, semi-gloss enhance its appearance and to provide film-forming finish such as lacquer or and gloss. The gloss paints are generally protection from surface degradation due varnish is used, many finish manufacturers the easiest to clean but should not be to moisture. recommend that a sealer be applied prior used in areas of high humidity. Exposure 1 OSB sheathing may also be to topcoating. Be sure to try the finish on Expected Results and Performance used as a substrate for stucco coatings a representative sample of the panel before OSB sheathing panels can be expected to when the panels are applied in accor- proceeding with the entire job. maintain their integrity and appearance dance with APA recommendations and Semitransparent Stains. Semitransparent when finished according to the above the coating in accordance with the speci- stains impart color to the wood surface procedures and used in interior applica- fications of the coating manufacturer. while allowing the wood grain and panel tions where they are not exposed to However, high performance elastomeric texture to show through. Oil-based stains drastic changes in moisture or to physical coatings should only be applied to are generally the most effective in achiev- abuse. As with any product, the service Exterior panels.

APA The Engineered Wood Association requirements and expected appearance are in a stack. Any panel edges which We have field representatives in should be considered when selecting the are subsequently cut should most major U.S. cities and in Canada who appropriate finish. Always consult the also be so protected. can help answer questions involving APA trademarked products. For additional finish manufacturer’s recommendations. assistance in specifying APA engineered Expected Results and Performance wood products, contact us: Try the finish on a representative sample Swelling of panel edges and uneven APA – THE ENGINEERED before proceeding with the entire job. swelling of individual wood particles or WOOD ASSOCIATION HEADQUARTERS High humidity areas such as kitchens or chips may be expected on OSB sheathing 7011 So. 19th St. Tacoma, Washington 98466 bathrooms can affect finish performance panels exposed to high moisture condi- (253) 565-6600 Fax: (253) 565-7265

in a manner similar to outdoor exposure. tions. This can cause a rough, uneven Addre eb ss OSB sheathing panels used in these types surface that may detract from the appear- W@ : of areas should be edge protected with a ance of smooth panels. Some cracking of www.apawood.org sealer compatible with the finish applied the finish and lifting of wood chips may PRODUCT SUPPORT HELP DESK to the panel surface. Only acrylic latex also occur. (253) 620-7400 paint systems should be used in high E-mail Address: [email protected] humidity areas. Because this type of Summary The product use recommendations in this finish tends to block (stick to itself), publication are based on APA – The OSB sheathing panels may be used for Engineered Wood Association’s continuing finished OSB sheathing should not be programs of laboratory testing, product most interior applications. Selection of research, and comprehensive field experi- used in cabinetry or shelving if high ence. However, because the Association has finish is primarily dependent upon the no control over quality of workmanship or humidity is expected. the conditions under which engineered wood desired appearance. Surface wax on some products are used, it cannot accept responsi- bility for product performance or designs as panels can interfere with application and actually constructed. Because engineered Finishing – Soffit Applications wood product performance requirements appearance of some finishes. Try the vary geographically, consult your local archi- tect, engineer or design professional to Exposure 1 OSB panels used for open finish on a representative sample prior to assure compliance with code, construction, soffits should be finished only with a proceeding with the entire job. OSB and performance requirements. top-quality acrylic latex house paint sheathing rated as Exposure 1 can be Form No. N300B Revised April 2001/0100 system composed of an acrylic latex used in outdoor applications where stain-blocking primer and a compatible exposure is on the underside, such as all-acrylic latex topcoat. All panel edges open soffits. In this type of application, should be protected with at least one panels should only be finished with a coat of the primer to be used on the top-quality acrylic latex house paint panel surface. This is usually accom- system consisting of an acrylic latex stain- plished most easily while the panels blocking primer and at least one all- acrylic latex topcoat. • ALL RIGHTS RESERVED. • ANY COPYING, MODIFICATION, DISTRIBUTION OR OTHER USE OF THIS PUBLICATION OTHER THAN AS EXPRESSLY AUTHORIZED BY APA IS PROHIBITED BY THE U.S. COPYRIGHT LAWS. THE U.S. IS PROHIBITED BY APA BY AUTHORIZED THAN AS EXPRESSLY OTHER USE OF THIS PUBLICATION DISTRIBUTION OR OTHER MODIFICATION, • ANY COPYING, • ALL RIGHTS RESERVED.

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