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Historic Preservation - Technical Procedures

Spectitle:
Applying A Water-Repellent Preservative To Wood

Procedure code:
0631001P

Source:
Developed For Hspg (Nps - Sero)

Division:
Wood And Plastics

Section:
Preservative Treatment

Last Modified:
02/24/2012

Details:
Applying A Water-Repellent Preservative To Wood



APPLYING A WATER-REPELLENT PRESERVATIVE TO WOOD


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on applying a water-
         repellent preservative (WRP) to wood.  This coating will
         prolong the service life of wood and provide some
         protection against agents of deterioration.

         NOTE:  WATER REPELLENTS AND WATER REPELLENT PRESERVATIVES
         ARE ONLY EFFECTIVE ON UNPAINTED WOOD.  IF IT IS APPLIED
         TO PREVIOUSLY PAINTED WOOD, BRUSH IT THOROUGHLY INTO ANY
         JOINTS OR CRACKS AND WIPE ANY EXCESS OFF PAINTED
         SURFACES.  ALLOW PROPER DRYING TIMES.

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

    C.   WRPs are often recommended for humid, southern climates.
         Their use can significantly reduce the problems of
         peeling, flaking, blistering, etc. of painted wood
         surfaces.

    D.   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

    E.   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.

    F.   See 01100-07-S for general project guidelines to be
         reviewed along with this procedure.  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)

         These guidelines should be reviewed prior to performing
         this procedure and should be followed, when applicable,
         along with recommendations from the Regional Historic
         Preservation Officer (RHPO).

1.02 DEFINITIONS

    A.   Water Repellent Preservatives (WRP):  

         1.   Natural, colorless liquids which, when brushed
              onto, or soaked into the wood render the wood
              impervious to liquid water, inhibit the growth of
              mildew and other fungi, and provide protection
              against termite and other insect infestation.

         2.   Their use reduces warping and checking and prevents
              water staining at edges of boards and at the end
              grain.  They do not, however, protect wood from
              water vapor or ultraviolet degradation.

         3.   WRP's will darken wood somewhat though in and of
              themselves, they contain no coloring agents.
              Though it varies with wood species the ultimate
              color is usually a golden tan.

         4.   WRP's can be used as a natural finish.

1.03 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:

         1.   Unless otherwise recommended by the manufacturer,
              the ambient temperature shall be between 50 degrees
              F. and 95 degrees F. 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 WRP 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 WRP's to damp surfaces, in misty or
              rainy weather, in the snow or where there is
              visible ice or frost on the surfaces.

1.04 MAINTENANCE

    A.   Water Repellent Preservative Finish (WRP):

         1.   On smooth wood surfaces, a water repellent
              preservative will remain effective for about a
              year.  If the first application was applied to the
              point of refusal, it may remain effective for two
              years.  On rough or weathered wood, expect a WRP to
              remain effective from one to three years.

         2.   To determine if it is still effective splash some
              water on the surface.  

              a.   If the water beads up the WRP is still
                   providing the necessary protection.  

              b.   If the water soaks into the wood, and/or the
                   wood has a blotchy appearance (caused by
                   mildew) it is necessary to retreat.

         3.   Before applying a new coat of WRP, clean the old
              surface with a nonferrous bristle brush.  

         4.   To kill any mildew, wash with a solution of 1/3 cup
              of household detergent (NO AMMONIA), 1 quart 5%
              bleach, and 3 quarts warm water.  

         5.   Rinse well and let dry thoroughly before reapplying
              the WRP.

         6.   After the treated wood has achieved a uniform tan
              color, retreatment will be required every 2 to 4
              years.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   American Building Restoration Chemicals, Inc.
         9720 South 60th Street
         Franklin, WI  53132
         800/346-7532 or 414/421-4125

2.02 MATERIALS

    NOTE:  SIMPLE WATER REPELLENTS (WR), BY THEMSELVES, DO NOT
    PROVIDE ADEQUATE PROTECTION AGAINST DECAY AND ULTRAVIOLET
    DEGRADATION AND ARE NOT TO BE USED AS THE SOLE FINISH.

    A.   Commercial water-repellent preservative such as "X-100
         Natural Seal" (American Building Restoration Chemicals,
         Inc.), or approved equal.

         -OR-

         A home-made preservative based on the USDA Forest
         Products Laboratory formula (see 06310-01-S for guidance
         on preparation).

    B.   Household detergent (NO AMMONIA)

    C.   Household Bleach:

         1.   Other chemical or common names include Sodium
              Hypochlorite (NaOCl); Bleaching solution*; Laundry
              bleach*; Solution of chlorinated soda*.

         2.   Potential Hazards:  CORROSIVE TO FLESH.

         3.   Available from chemical supply house, grocery store
              or supermarket, hardware store or janitorial supply
              distributor.

    D.   Clean, clear water

2.03 EQUIPMENT

    A.   Brushes:

         1.   Use natural bristle paint brushes for oil/alkyd
              stains.  Precondition by soaking in raw linseed oil
              for 24 hours.  Use nylon bristle brushes for latex
              stains.  Do not use the same brush for both types
              of stain.

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

         3.   Stiff natural bristle scrub brushes.


PART 3---EXECUTION

3.01 PREPARATION

    A.   Surface Preparation:  The surface should be free of all
         loose fibers, dust and grease before application of a
         WRP.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Prepare the Water-Repellent Preservative (Forest Products
         Laboratory formula).  See 06310-01-S for guidance.

         -OR-

         Use one of the proprietary products listed above.

         NOTE:  ON A SMOOTH SURFACE 1 GALLON OF WRP WILL COVER
         APPROXIMATELY 250 SF.  IT WILL COVER APPROXIMATELY
         100-150 SF ON A ROUGH SURFACE.

    B.   Dipping is the most effective means of treatment,
         especially for the ends of wood members.  Brushing, to
         the point of refusal, is the next best method of
         treatment.  

         1.   For treated lumber, dip freshly cut surfaces before
              installation, 10 seconds to 3 minutes.

         2.   For untreated lumber, dip, brush or spray with
              preservative.  Pay particular attention to end
              grain and joints.

         3.   For wood shingles, dip before installation, with a
              second coat brushed onto the surface after
              installation.

         4.   On fixed surfaces, use a minimum of two successive
              coats.

         5.   For pieces that are removable, soak for 10 seconds
              to 3 minutes.

    C.   Allow adequate time to dry before repainting so that
         paint will adhere properly.  Follow manufacturer's
         instructions.  

         1.   In general, if the surfaces have been brush
              treated, 48 hours at 70oF. is generally sufficient
              drying time.  

         2.   Longer drying times will be required if it gets
              colder than 70oF. at any time during this drying
              period.  

         3.   Wood that has been dipped for 10 seconds will need
              a minimum of one week of similar, ideal drying
              time.  

         4.   If work is being done late in the year and it is
              too cold in the evenings for a paint film to dry
              properly, only apply a WRP and wait until spring to
              prime and paint.

    D.   In addition to adequate drying times, some WR/WRP's must
         be allowed to weather before painting.  Follow
         manufacturer's instructions.  Time can vary from six
         months to two years.

3.03 ADJUSTING/CLEANING

    A.   Caulking joints is an important part of surface
         preparation.  Also caulk after a WR or WRP has been
         applied.

                         END OF SECTION