John Leeke's Historic HomeWorks™
207 773-2306 26 Higgins St. Portland, ME 04103
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John Leeke's Historic HomeWorks™ |
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207 773-2306 26 Higgins St. Portland, ME 04103 |
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| [Home][Library][Restoration Reports][Seminars][Forum][Internships][Office][Workshop][Front Porch][Search] info.© 1994-2009 JohnC.Leeke |
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"Painting
Recommendations For Pre-Primed, Medium Density, Hardboard
Siding"
Joint Coatings/Forest Products Committee
Chairman: Steve Bussjaeger, HIS Paint Manufacturing Co. Inc.,
Oklahoma City, OK (1-405-232-2077) Ken Peterson, Georgia-Pacific
Corporation, Atlanta, GA Harry Warren, Masonite Corporation,
Chicago, IL
Introduction..........(Return to
Table of Contents)
Definition of Hardboard Siding and Manufacturing Process
Hardboard is a generic term for a panel manufactured primarily
from interfelted ligno-cellulose fibers consolidated under heat
and pressure in a hot press to a density of at least 31 lbs. per
cubic foot (pcf). Other materials may be added during manufacture
to improve certain properties, such as stiffness, hardness,
finishing properties, resistance to abrasion and moisture, as
well as to increase strength, durability and utility. [1]
Hardboard is used in a variety of exterior and interior
applications and has become a major factor in markets that were
predominately held by plywood or lumber.
There are two basic manufacturing processes for exterior medium
density hardboard siding, and a third process combines certain
aspects of the other two. There are wet, dry, and wet-dry
processes. In all of these, the manufacturing process is similar
in nature and produces a product with some advantages and
limitations when compared to solid wood. Hardboard is less prone
to grain raising, splitting, cracking, and warping. However, its
dimensional stability in some directions is much less than solid
wood [2]. Density of hardboard is typically in the 43-60 pcf
range[3], whereas woods such as western red cedar and southern
yellow pine will generally range from 22-38 pcf [4].
Types of Hardboard Siding and Their Uses
Exterior hardboard is primarily available in 4 foot by 8-foot
panels or 16 foot length lap siding in varying widths. Panel or
lap siding that is to be finished by the consumer can generally
be found in one of the two following categories.
1. Smooth/pre-primed: no texture with a factory applied primer.
2. Textured/pre-primed: an embossed surface with a factory
applied primer.
Pre-primed and unfinished hardboard can also be found to be a
major component in many flush and panel garage door products.
Regardless of end use application, the majority of hardboard that
is going to be field finished is of the "pre-primed"
(factory-applied primer) variety which is generally based on a
flat or low sheen, thermoset or thermoplastic acrylic emulsion
coating.
Exterior overlaid oriented strand-board (OSB) is another type of
pre-primed lap and panel siding. Once installed, this similar
appearing material may be mistaken for medium density hardboard
siding. However, OSB's composition and physical properties are
different and are considered to be in the structural panel
category. OSB's finishing characteristics are similar to that of
hardboard, although coating performance on OSB siding material is
not widely documented.
Products Used To Finish New
Pre-Primed Hardboard Siding..........(Return to Table of Contents)
Primers and Topcoats and Their Selection
There are a variety of paints available today for exterior
finishing. Paints are either water-thinned or organic
solvent-thinned. Latex paints are water-thinned and are a popular
choice. They offer water clean-up of equipment and generally
better overall performance over organic solvent-thinned oil/alkyd
paints. Latex paints dry quickly and exhibit better color and
gloss retention, mildew and blister resistance and long term
flexibility than oil/alkyd finishes. Oil/alkyd finishes offer
good moisture barrier, high dry film build, good adhesion and can
be applied at lower application temperatures than latexes. Latex
and oil/alkyds are available in an unlimited number of colors and
a variety of sheens from flat to gloss.
A primer is a coating formulated to provide a sound base upon
which subsequent coatings can be applied. Oil/alkyd solvent based
or stain-blocking latex primers are both acceptable to coat the
face and edges of exterior hardboard.
Topcoat selection should be limited to paints and heavy-bodied,
solid-color latex stains. Clear and semitransparent finishes,
latex or oil, are not recommended. These finishes do not offer
adequate film build for long term substrate protection. Acrylic
latex house paints will frequently give the longest service life
in terms of protection and decoration.
Proper coating selection will assure long term protection of
hardboard. A two coat, field applied finishing system is
essential for good performance over factory primed siding.
Applying one coat of finish will not give adequate protection on
new installations and can result in premature coating and/or
hardboard failure. Studies have shown that a two coat, field
applied system consisting of one coat primer, one coat topcoat
will generally outperform a two coat system of two coats of
topcoat. Two and three coat field applied finishing systems will
give best overall performance on pre-primed hardboard siding
[5,6,7].
New hardboard garage doors need to be finished in the following
manner. Pre-primed surfaces should be coated with one coat primer
and one coat of topcoat. Any unprimed (no factory primer)
hardboard or wood sections require a field application of one
coat primer plus two coats of topcoat. It is important to coat
the outside, inside and all edges of the garage door [8].
Regardless of the brand chosen, only top line quality paint, such
as acrylic latex, should be used. The few dollars saved do not
justify the shorter coating life one will obtain with a lesser
quality paint. All finish types for use on hardboard siding,
primer and topcoat, should be those recommended by the paint
manufacturer, as well as the specific hardboard supplier.
Surface Preparation and Application
The first step prior to finishing new pre-primed hardboard is to
prepare the surface properly. All foreign matter such as mud
flecks, dust, dirt, footprints and other contaminants should be
removed with a mild detergent (i.e., trisodium phosphate--TSP)
solution and thoroughly rinsed with clean water. Hardboard should
be clean, dry and mildew free prior to paint application and
should be finished as soon as installation is completed. All
edges of hardboard should be primed at installation, especially
any cut edges. When installation is complete, spot prime any bare
or damaged areas. After initial spot priming has dried, follow
with a full coat of primer. The topcoat should be compatible with
the primer and a full coat should be applied after the primer has
adequately dried. A dry film thickness of 3.0-50 dry mils of
field applied coating is recommended for a two-coat system. If
pre-primed siding is not finished within 60 days after
installation, a field-applied system consisting of one coat
primer, followed by two coats of topcoat is recommended [9].
Coatings should be selected and applied according to the paint
and hardboard manufacturers' instructions either by brush, roller
or airless spray. Proper film thickness must be uniformly applied
to all drip edges, grooves and facing of the siding.
Performace Expectations
and Refinishing Considerations..........(Return to
Table of Contents)
Maintenance and Refinishing of Previously Coated Hardboard
Inspect the home exterior on an annual basis. Check for
weather-eroded, chalked, loose, cracked or peeling paint. Mildew,
nail stains, pigment fading, dirt accumulation and wax migration
are forms of discoloration that may require refinishing. Look for
cracks, open joints or failed caulking where water may enter. If
any of the above conditions exist, they should be rectified as
soon as possible to simplify refinishing and minimize potential
siding damage. Exterior finishes usually weather most rapidly on
the south and west sides of the structure. The frequency of
refinishing may be in the one to eight-year range, however,
refinishing will depend on local climatic conditions, paint
quality, dry film thickness, color of the coating previously
applied and adherence to paint manufacturer's instructions.
In many cases early or premature repainting becomes necessary due
to using inferior bargain paints, uneven or thin paint film
thickness, improper surface preparation or moisture problems from
poor construction practices.
Surface Preparation
Many times early finish failure on a repaint job is due to
improper surface preparation. Final repainting results will be
more attractive and long lasting with proper surface preparation.
· Dirt, Chalk and Under Eave Deposits: Remove these deposits by
washing with a detergent solution (TSP) or commercial cleaner
recommended for cleaning painted surfaces using a sponge or
brush. Protected areas such as under eaves and overhangs need
special attention to remove invisible deposits that can promote a
premature peeling problem. After washing, thoroughly rinse with
clean water and allow to dry. Power washing the surface is also a
fast, effective method of removing dirt, chalk, etc. If a power
washer is used, follow the manufacturer's recommendations and
warnings.
· Mildew: Spotty patches that look like dirt, but do not come
off when scrubbed with detergent solution are probably mildew.
Mildew can occur on any side of the house, but is more likely to
grow in shaded areas or behind shrubbery. It can easily be
identified from other forms of discoloration by applying a few
drops of bleach. If mildew is present the black, gray or brown
color will bleach out and disappear within one or two minutes.
Mildew must be killed and removed before repainting. If the
mildew is not completely removed, the active spores will continue
to grow and may almost immediately begin to reappear on a
recently repainted surface. Where mildew is present, apply a
solution of 1 part household bleach and 3 parts water or use a
commercial mildew remover. It is mandatory to wear rubber gloves,
goggles, long-sleeved shirt and long pants to protect eyes and
skin when using a mildew remover. In addition, protect grass,
trees and shrubs with plastic covers. CAUTION!! DO NOT MIX BLEACH
WITH AMMONIA, OR DETERGENTS CONTAINING AMMONIA. Follow specific
instructions if a commercial mildew remover is used.
· Wax Migration: If a stain or discoloration persists after
removing dirt and/or mildew, it may be a wax migration from the
siding. It can be identified by applying a few drops of water,
both to a discolored area and an adjacent non-discolored area. If
the water beads on the discolored area, but spreads or is
absorbed in the areas around the stain, a wax migration condition
probably exists in the stained area.[10] In most cases this
discoloration can be removed with a hot detergent solution (TSP),
followed with a thorough rinsing with clean water. In extreme
cases, removing the stain by wiping the area with a clean rag wet
with mineral spirits may be necessary, followed by a detergent
solution (TSP) wash and clean water rinse. Repeating either
process may be necessary until clear water ceases to bead up on
the affected area. Prime the affected area prior to topcoating.
· Loose and Peeling Paint: Remove by scraping, stiff bristle
brushing or power washing the surface. Feather sand to smooth
edges of peeled spots. Spot prime all bare areas.
· Rusty/Loose Nails: Replace loose nails with slightly larger
galvanized nails. Leave nail heads flush with surface and prime
with an oil-based primer.
· Cracks, Splits and Open Joints: Cracks or open joints where
water may enter should be caulked with a high quality, paintable
acrylic caulk. Apply primer over caulked area.
· Glossy Areas: Dull surfaces by scuff sanding with sandpaper.
· Dents or Gouges: Fill with exterior grade spackle and sand
smooth when spackle has dried hard.
· After steps have been taken to correct any problem areas, the
finish coat can be applied. Normally one full coat of finish is
adequate. However, two coats will offer better protection and
durability, or may be necessary in the event of an extreme color
change from the previous color being recoated.
Select only top-of-the-line quality finishes.
Test Methods..........(Return to
Table of Contents)
ANSI/AHA A135.6 covers requirements and methods of test for
hardboard physical characteristics such as water absorption,
thickness swell, hardness, and weatherability of pre-primed
substrate.[11] Correlating coating and substrate physical data
and artificial weathering test methods to actual exterior coating
performance is not an exact science. In many cases coating
adhesion, hardboard density, accelerated weatherometer and other
short-term testing methods exhibit poor statistical correlation
to actual outdoor weathering [7]. The most reliable predictor of
finish performance is actual outdoor exposure. North and south
exposures in different geographical areas will give the best
insight into a system's performance in terms of longevity, color
retention, mildew resistance, chalk resistance, etc.
Exposure fence studies demonstrate latex finishes based on low
quality polymers exhibit a higher rate of failure versus those
based on higher quality, acrylic based polymers.[5,6,7] Exposure
work can be accelerated by the use of a 45 degree angle south
test fence in a climate with moderate moisture, where systems
will be exposed to hot summers and days of freeze-thaw during the
year.
Field Hints..........(Return to
Table of Contents)
Surface Preparation, Application and Equipment
1. Read manufacturer's label instructions and warnings on all
paints, equipment and miscellaneous items prior to using. Label
instructions should cover specific recommendations on surface
preparation, spread rates, proper applicators and application
conditions, etc.
2. Dispose of spent solvents, etc. according to local and state
regulations.
3. Clean up spills promptly as they occur. Allow sufficient time
toward the end of the day to clean equipment thoroughly. Follow
cleaning instructions found on the paint can label.
4. For lap siding, work from top to bottom. Go side to side
extending it to the next corner or to an intervening door or
window. At the end of the day, stop work at a natural boundary to
prevent lap marks. Coat the drip edge (bottom edge) of the lap
first with a generous coat.
5. For grooved or batten siding, paint the grooves and battens
first and then paint the adjoining flat surfaces.
Research Needs..........(Return to
Table of Contents)
With the increase in regulations concerning volatile organic
compounds (VOC), moves have been made to reduce the solvent level
of oil-based primers and topcoats. Additional research is needed
to evaluate the performance characteristics of VOC-compliant
solvent-based systems for their potential use on exterior
hardboard siding. Accelerated test methods need to be established
to predict coating/pre-primed hardboard performance and
interactions. The ability to accurately predict a coatings
system's potential is needed to assure long term protection of
the substrate. Short term weathering of natural wood siding
products prior to finishing has detrimental effects on coating
performance.[12] Weathering of pre-primed hardboard prior to
finishing and its effect on finish and substrate performance is a
concern since little documentation exists.
Summary..........(Return to
Table of Contents)
Proper painting of pre-primed hardboard siding will do more than
simply create an attractive appearance. It will provide
protection from the sun, weather and other environmental factors
that can damage the structure. Best long-term performance of
coatings and hardboard siding can be expected when top quality
surface preparation, finishes, tools and workmanship are used.
A minimum two coat, field applied system is required for adequate
coating performance and substrate protection. Field applying a
three-coat system (one coat primer, two coats topcoat) will
enhance long term performance.
It is imperative to read and follow both the paint and hardboard
suppliers' recommendations. Paint manufacturers' recommendations
can vary regarding types of primers, topcoats or coating systems
that are acceptable for use on hardboard. The same holds true for
hardboard producers on the acceptable types of primers, topcoats
or coating systems that are recommended for their specific
sidings.
Acknowledgement..........(Return to
Table of Contents)
The Hardboard Task Group Committee wishes to thank the
contributing Joint Committee members from the Federation of
Societies for Coatings Technology and National Forest Products
Association for their valuable time and cooperation.
References..........(Return to
Table of Contents)
1. American Hardboard Association, "Today's Hardboard,"
March, 1988.
2. Tooley, J., "Characteristics of the Substrate and Future
Developments," presented at the O'Hare Hilton, Chicago, IL,
Sept.27, 1988.
3. Biblis, E.J., "Engineering Properties of Commercial
Hardboard Siding. Part 1. Embossed Panels," Forest Products
Journal, Volume 39, No. 9, September (1989).
4. Cassens, D.L. and Feist, W.C., "Finishing Wood
Exteriors," USDA Agr. Handbook, No. 647, May (1986).
5. Kansas City Society for Coatings Technology, "Performance
Comparison of Exterior Flat Finishes on Hardboard Siding,"
Journal of Coatings Technology, 56, No. 711, 19 (1984).
6. Kansas City Society for Coatings Technology, "Performance
of Exterior Flat Finishes on Medium Density Hardboard
Siding," Journal of Coatings Technology, 61, No. 711, 39
(1989).
7. Kansas City Society for Coatings Technology, "Performance
Comparison of Exterior Finishes on Hardboard Siding,"
Journal of Coatings Technology, 62, No. 789, 133 (1990).
8. American Hardboard Association, "Finishing
Recommendations for Hardboard Garage Doors / Flush and
Panel," November, 1986.
9. American Hardboard Association, "Finishing
Recommendations for New Construction Utilizing Unprimed and
Primed Hardboard Siding," July, 1988.
10. National Decorating Products Association, "Paint Problem
Solver," 1983.
11. American Hardboard Association, "Hardboard
Siding-ANSI/AHA A135.6-1989," September 1989.
12. Schurr, G.G., "Exterior House Paint, Federation Series
on Coatings Technology, Unit 24", 1977
Additional Sources of
Information..........(Return to Table of Contents)
American Hardboard Association
520 North Hicks Road, Palatine, IL 60067
Federation of Societies For Coating Technology
492 Norristown Road, Blue Bell, PA 19422-2350
Forest Products Research Society
2801 Marshall Court, Madison, WI 53705
National Decorating Products Association
1050 N. Lindbergh Blvd., St. Louis, MO 63132
National Forest Products Association
1250 Connecticut Ave., N.W., Washington, D.C. 20036
National Paint And Coatings Association
1500 Rhode Island Avenue, N.W., Washington, D.C. 20005
USDA Forest Products Laboratory
One Gifford Pinchot Drive, Madison, WI 53705
Webpage creation by Dan Mitchell, working in
the Historic Home Works Assistantship Program. Dan is a
preservation enthusiast on Cobbosseeconte Lake in Maine.
(Return to the List of Articles)
|
John Leeke's Historic HomeWorks™ |
|
207 773-2306 26 Higgins St. Portland, ME 04103 |
|
| [Home][Library][Restoration Reports][Seminars][Forum][Internships][Office][Workshop][Front Porch][Search] info.© 1994-2009 JohnC.Leeke |