Applying a Semi-Transparent or Opaque Stain to Wood

PART 1–GENERAL

1.01 SUMMARY

1. This specification provides guidance on applying a semi- transparent or opaque stain to wood surfaces. This coating will prolong the service life of wood and provide some protection against agents of deterioration.

2. NOTE: IF THE WOOD WAS ORIGINALLY FINISHED WITH A FULL-BODY PAINT, IT SHOULD BE REPAINTED RATHER THAN STAINED, AS THE VISUAL APPEARANCE OF STAIN IS NOT COMPATIBLE WITH THAT OF PAINT. HOWEVER, SOME STAINS MAY BE SUITABLE REPLACEMENTS FOR WHITEWASH PAINT. CONSULT THE REGIONAL HISTORIC PRESERVATION OFFICER (RHPO) FOR GUIDANCE AND RECOMMENDATIONS.

3. Natural causes of wood deterioration include decay, ultraviolet degradation, insect infestation and excess moisture.

4. Some types of problems resulting from the weathering process include:

   1. Fungi and/or mildew growth.

   2. Warped boards.

   3. Loose fasteners.

   4. Changes in surface texture resulting in cracks and checks.

5. In addition to opaque paints, various so-called “natural” finishes and colored stains provide this necessary protection. And, like paints, proper surface preparation and application are vital to long lasting protection.

6. See “General Project Guidelines”. These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the RHPO. These guidelines cover the following sections:

   1. Safety Precautions

   2. Historic Structures Precautions

   3. Submittals

   4. Quality Assurance

   5. Delivery, Storage and Handling

   6. Project/Site Conditions

   7. Sequencing and Scheduling

   8. General Protection (Surface and Surrounding)

1.02 DEFINITIONS

1. Semi-Transparent Penetrating Stains: Thin, moderately-pigmented water repellents and water-repellent preservatives (WRPs) that penetrate the wood, thereby allowing the natural grain and texture to show through.

   1. The addition of the pigment protects the wood against ultraviolet degradation and increases the durability of the finish.

   2. Semi-transparent penetrating stains made from WRPs are recommended because:

      1. They provide additional protection against decay.

      2. They penetrate the wood rather than forming a film.

      3. They will not peel, flake or blister.

2. Solid Color (Opaque) Stains: Provide an opaque finish with a slightly lower concentration of pigment than regular paints.

   1. They result in a flat finish which hides the natural color and grain of the wood but maintain the original texture.

   2. Oil-based or acrylic-based (acrylic-based recommended).

   3. They form a thin film on the surface of the wood and are therefore subject to peeling, flaking, etc., just as paint is.

1.03 DELIVERY, STORAGE AND HANDLING

1. Stains shall be in sealed containers that legibly show the designated name, formula or specification number, batch number, color, quantity, date of manufacture, manufacturer’s formulation number, and manufacturer’s directions, including any warnings and special precautions and name of manufacturer.

2. Stains shall be stored on the project site and shall be stored to prevent freezing.

3. Stains shall be kept covered and safeguards taken to prevent fire.

1.04 PROJECT/SITE CONDITIONS

Environmental Requirements:

1. Unless otherwise recommended by the manufacturer, the ambient temperature shall be between 50 degrees Fahrenheit and 95 degrees Fahrenheit when applying either a stain or WRP.

2. Do not apply when the relative humidity exceeds 85% or the moisture content of the wood exceeds 12% as measured by an electronic moisture meter.

3. Do not apply a stain in the direct sun. They shall be applied only when the surface to be treated is in the shade and the sun is shining on the opposite elevation. The west elevation should be treated in the morning when the sun is shining on the east elevation; the north elevation should be treated around noon when the sun is shining on the south elevation; the east elevation should be treated in the afternoon when the sun is shining on the west elevation; and the south elevation should be treated late in the afternoon when it is in full shade.

4. Do not apply stains to damp surfaces, in misty or rainy weather, in the snow or where there is visible ice or frost on the surfaces.

5. For optimal results when using a latex stain do not apply when the temperature is expected to go below 50 degrees Fahrenheit within 24 hours of application. To prevent the stain from drying too quickly on hot, dry days, the surface can be slightly dampened before the application of a latex stain. Be sure to follow all manufacturers’ instructions.

1.05 MAINTENANCE

Maintenance of Semi-Transparent Penetrating Oil-Based Stains Finish:

1. The life expectancy of these stains varies tremendously depending on whether one coat or two coats of stain were applied initially. A single coat, applied to smooth wood should last 2 to 4 years.

2. A two-coat system, however, should last up to 8 years depending on the exposure.

3. Coastal exposures or cold environments especially at high altitudes will deteriorate more quickly, as will most southern exposures.

4. A loss of color is a good indication that the finish must be renewed.

5. Clean surfaces with a stiff, nonferrous bristle brush to remove dirt and loose wood fibers.

6. If the surface has mildewed, wash with bleach and detergent, rinse and let dry completely before applying a new coat of stain.

7. NOTE: Because weathered wood is more porous and will therefore allow stain to penetrate more, subsequent applications of stain will last longer than the initial application.

PART 2–PRODUCTS

2.01 MANUFACTURERS

1. Benjamin Moore

Montvale, NJ 07645

855-724-6802

2. Cabot Premium Woodcare

Salem, NH 03079

1-800-877-8246

3. PPG Architectural Coatings

1-800-441-9695

4. Sherwin-Williams

Cleveland, OH

216-566-2000

2.02 MATERIALS

NOTE: All stains shall be from the same manufacturer to avoid problems with penetration and coverage. Different batches of stain, even from the same manufacturer, should also be avoided for the same reasons.

1. Oil-modified alkyd semi-transparent penetrating stain such as “Acri-Shield Deck, Fence & Siding Alkyd/Oil Semi-Transparent Stain” (PPG Architectural Coatings), or approved equal. Other manufacturers are listed in Section 2.01 above.

   1. Oil/alkyd-based semi-transparent penetrating stains, which contain a wood preservative, are recommended for use over latex-based products. Latex-based stains do not penetrate the surface and are subject to peeling, flaking, etc.

   2. These stains are most effective on rough lumber and plywood, smooth lumber, weathered wood and flat-grained surfaces of dense species that do not hold paint well.

   3. They can also be used over other penetrating finishes which have weathered to the point of needing to be renewed.

   4. Do not apply over paint, solid- color (opaque) stains or varnish, or on smooth plywood.

2. -OR-

   Solid color (opaque) stain

   1. Though both oil- and acrylic-based solid color stains are available, the acrylic-based stains are recommended here and by the USDA’s Forest Products Laboratory.

   2. Opaque stains are recommended for:

      1. Transitioning from a semitransparent penetrating stain or an opaque oil stain to a lighter color.

      2. Covering a previously creosoted surface.

      3. Covering new, close-pored wood species such as Southern yellow pine.

   3. Like latex paint, acrylic-based opaque stains are also more resistant to mildew, easy to apply and easy to clean-up with soap and water.

   4. Oil-based opaque stains may be successfully used on fresh, clean wood

   5. Oil-based opaque stains are NOT recommended for:

      1. Previously-painted wood, even if all of the paint has been removed.

      2. Reapplication over existing oil-based opaque stains.

      3. In both cases an uneven, splotchy appearance can be the result.

   6. Solid color stains, either oil- or latex-based, are NOT recommended for flat, horizontal surfaces such as window sills, handrails, porch floors, or decks.

2. One of the following types of caulking compounds:

   1. Polyurethanes

      1. Easily workable.

      2. Paintable.

      3. 15-20 year lifespan.

      4. Limited availability, see Section 2.01.

   2. Polysulfides

      1. Slow-drying.

      2. Paintable.

      3. Can be sanded.

      4. Highly elastic.

      5. Limited availability, see Section 2.01.

   3. Butyls

      1. Paintable.

      2. Cannot be sanded.

      3. 7-10 year lifespan.

   4. Silicones

      1. Some can be painted.

      2. Generally not sanded.

   5. Acrylic Latex

      1. For exterior work.

      2. Should generally be limited to application on tight, narrow joints.

      3. Short lifespan.

2.03 EQUIPMENT

Brushes:

1. Use natural bristle paint brushes for oil/alkyd stains. Precondition by soaking in raw linseed oil for 24 hours.

2. Use nylon bristle brushes for latex stains.

3. Do not use the same brush for both types of stain.

4. For thin, runny stains, foam pad applicators can be used.

5. Stiff natural bristle scrub brushes should also be on hand.

PART 3–EXECUTION

3.01 PREPARATION

Surface Preparation: Like any paint system, the surface to be treated must be clean and free of any loose, rough wood fibers, loose paint or varnish, mildew, grease and dust. The surface must be as meticulously prepared for a stain as it would be if it were being painted. See “Surface Preparation for Painting Wood” for guidance on preparing wood surfaces for recoating.

3.02 ERECTION, INSTALLATION, APPLICATION

1. Mixing the Stain:

   1. Pour off the top oils to a smaller container.

   2. Stir the remaining contents until well-mixed.

   3. Add back the top oils and mix thoroughly again.

   4. If possible, mix the entire amount in one container, i.e. use a five-gallon paint bucket to mix 2-3 gallons of stain. This will allow more vigorous and thorough mixing without fear of spilling.

   5. When the first batch of stain is about 2/3 gone, stir the remaining stain into a new batch of stain. This will help even out any differences in color and pigment concentrations between cans.

   6. Throughout the application, stir the stain often to keep the pigments and oils well-mixed.

2. Applying a semi-transparent (oil-based) penetrating stain:

   1. NOTE: The application of a semi-transparent penetrating stain is best performed with a brush. Sprayers and rollers may be used but it is difficult to achieve using either of these methods. For stains that are especially thin, foam applicators will help control the application.

   2. When using a commercial stain, follow all manufacturers’ instructions.

   3. One gallon of a semi-transparent oil-based penetrating stain will cover approximately 200-400 square feet when applied to a smooth surface, and 100-200 square feet when applied to a rough or weathered surface.

   4. For dense species of wood such as Douglas fir or Southern pine, let the wood weather for a year before staining.

      1. Prior to allowing the wood to sit for a year, treat it with a WRP. See “Applying a Water-Repellent Preservative to Wood” for guidance.

      2. By allowing the wood to sit for a year, its surface becomes more porous, allowing the first coat of stain to penetrate more deeply and resulting in a more durable finish.

   5. Start at the top of the area to be stained and work down, applying the stain to a small number of boards or a single panel at a time. This will help avoid lap marks. If possible, stop at a logical breaking point such as the end of a clapboard or at a door or window.

   6. NOTE: DO NOT LET THE FRONT EDGE OF A FRESHLY-STAINED AREA TO DRY BEFORE BEGINNING THE NEXT SECTION.

   7. For rough or weathered surfaces, apply two (2) successive coats of the stain.

      1. Brush on the first coat of stain, again working in small, logical areas. Allow each coat to soak into the wood for 20 to 60 minutes before applying the second coat, but do not allow the first to dry completely.

      2. About an hour after the application of the second coat of stain wipe off any excess stain with a cloth, sponge, or brush which has been slightly dampened with the stain.

   8. When staining over a weathered penetrating natural finish, brush with a stiff bristle brush to remove dust and loose wood fibers.

   9. NOTE: Do not use ferrous brushes or wools. These can leave small iron particles on the surface of the wood.

      1. Certain water-soluble extractives naturally found in some woods such as western red cedar, redwood, Douglas fir and oak can react with the iron particles, causing blue-black staining.

      2. Pentachlorophenol, a common wood preservative often found in some WRPs and semi-transparent penetrating stains, can also cause loose iron particles to corrode, which will also result in blue-black staining.

   10. After applying the new coat of stain, carefully examine the surface.

       1. A dull, flat surface will indicate that the stain has evenly penetrated the wood.

       2. A slightly glossy surface will indicate that penetration of the stain was uneven resulting in a less durable surface which will need to be renewed more often.

   11. During application, if it is possible, remove any trim pieces which are to be stained a different color because it is difficult to cut in stain.

   12. For better control and more even coverage and penetration, pre-stain any new wood.

3. Applying a solid color (opaque) stain:

   1. NOTE: Opaque stains react much the same way as do oil-based and latex paints. Brush application is the best but a roller may also be used.

   2. Follow the same procedures outlined for semi-transparent penetrating stains in Section 3.02 B. above.

3.03 ADJUSTING/CLEANING

Apply any caulk after staining has been complete and water repellent or WRP has been applied, because caulks are not stainable.