Finishes, Stains, Coatings, & Preservatives for Decks
DECK FINISHES COATINGS PRESERVATIVES - CONTENTS: Wood deck finishes and stains - selection, recommendations, types. Colors & Pigmented Finishes for Exterior Decks. Water repellent coatings for wood decks. Using semi-transparent stains on wood decks. Painting decks. Using solid pigmented stains on wood decks. List of manufacturers of wood deck coatings, preservatives, stains
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This article discusses the selection and application of deck stains, water repellents, paints, or other coatings.
Our page top photo shows a weathered-gray deck that was the subject of owner-complaints concerning black "mold" spots. It was determined that wax from citronella candles spilling on the surface was the culprit.
All wood decking, whether pressure-treated or not, needs
to be sealed at installation and periodically thereafter to
prevent checking, warping, and deterioration of the surface
due to exposure to water and sunlight. The chemicals
in treated wood and the natural tannins in redwood and
cedar resist decay and insect attack, but they will not stop
checking and warping.
There are a wide array of deck
finishes on the market, but they all consist of one or
more of the following: water repellants, preservatives,
UV blockers, pigments, and a drying oil or varnish base
(see Table 4-9.)
[Click any image for an enlarged, detailed version.]
Water Repellants for Wood Decks
At a minimum, all wood decks should be treated with a
water-repellant coating, preferably a water-repellant preservative
(WRP), which has an added mildewcide.
called “sealers,” these formulations typically contain a
water-repelling wax and a varnish or drying oil, such as
linseed or tung oil. The finish penetrates and seals the
wood surface, reducing the amount of water absorption
and thereby protecting against checking, splitting, and
warping. After application, water should bead up as on a
newly waxed car.
Some water repellants contain a small amount of wax
(about 1% by volume) and are intended as a pretreatment
for other finishes.
Others contain up to 3% wax and are intended
as a final coating. Some of these cannot be stained
or painted over, so it is important to read the label.
WRPs, which have an added mildewcide [really it's a fungicide since mildew grows only on living plants], help prevent
dark stains on natural woods like redwood and cedar, and
on pressure-treated lumber as well. In addition, WRPs provide
some protection against decay in the sapwood of redwood
and cedar and in the cut ends of pressure-treated
Some sealers and WRPs also have UV-inhibitors,
an important addition if the sealer is the final coating, since
this will help protect against deterioration of the wood
surface from sunlight.
If a sealer or WRP is the only treatment used, the
homeowner should plan to recoat every one to two years
or whenever water on the surface no longer beads up and
is quickly absorbed.
WRPs also make an excellent undercoat
for semitransparent stains. The combination of a
semitransparent stain over a WRP base coat provides the
best long-term protection for decks. However, not all
WRPs are suitable for use as an undercoat—so check the
label or ask the manufacturer before proceeding.
Semitransparent Stains for Wood Decks
Oil-based semitransparent stains contain many of the same
ingredients as a WRP and penetrate the wood in the same
manner. The main difference is the addition of pigments,
which provide some color and help protect against
[The stained exterior deck shown at left has no guardrailings. Fortunately that's because its construction was incomplete - railings were added later.
Until the guardrails were installed this was an unsafe structure and should have had appropriately restricted access.
Some, such as Penofin (Performance Coatings
Inc.), are very lightly pigmented but add UV inhibitors
to achieve a similar level of protection.
Since oil based
stains penetrate the wood surface, they will not peel,
blister, or chip like paint. Stains formulated specifically
for decks may have improved resistance against abrasion
Stains are a good finish for either treated wood or
naturally decay-resistant species. The pigment provides
good protection against UV radiation and extends the life
of the finish beyond that of a simple water-repellant
or WRP. Light-colored finishes will reflect more light
and, therefore, tend to outlast darker colors on exposed
For the stain to penetrate properly, the wood surface
must be fairly dry when the stain is applied. If the decking
material was factory-treated with a sealer or was recently
sealed on-site, it may be necessary to wait two weeks or
longer before staining. For best results, apply two coats of
stain, with the second applied before the first coat completely
Once dried, the first coat will block the
proper penetration of the second coat.
Paints and Solid-Color Stains for Use on Wood Decks
Paints and solid color
stains (also called “opaque” stains), whether latex or
oil-based, all form films on the wood surface.
provide excellent protection against water penetration and
UV degradation, they are not recommended for decking (flooring)
for two main reasons:
They do not protect against decay
and they are prone to bubble, peel, and crack if moisture
does get through.
They can also peel or crack during the
initial drying of the wood.
While not recommended for the
decking, paint may be applied successfully to other deck
components, such as railings.
If the job calls for paint, take the following precautions:
First, seal the wood with a water-repellant preservative
formulated to serve as an undercoat. Make sure all end
grain is sealed and primed prior to assembly, when it may
After two to three weeks, when the
surface is dry enough to paint, prime and paint the rest of
the wood. A better alternative, if the budget allows, is to
buy kiln-dried pressure-treated lumber, which can be
sealed, primed, and painted immediately. Kiln-dried
pressure-treated lumber is marked KDAT (kiln-dried after
Woods such as redwood and cedar, which have a high
level of extractives, require special stain-blocking primers,
or the dark-colored extractives will bleed through and stain
the painted surface.
While painters have traditionally preferred
oil-based primers on wood species prone to extractive
bleeding, new latex primers specially formulated for
stain blocking may also do the job.
Deck & Porch Resources, Products, Manufacturers: Where to Buy
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Mark Morsching, Everflashing, Tel: 800-550-1667, Email: firstname.lastname@example.org. The Everflashing product comes in G-185 and Stainless Steel and is intended for use with treated lumber with copper in it. Everflashing produces a variety of specialty flashing products including flashings for use with decks at deck ledgers and deck perimeters.
Summerblue Arts Camp., Two Harbors MN, Lon Church, Director, c/o: Two Harbors High School
405 4Th Avenue, Two Harbors, Minnesota 55616, United States Email: email@example.com
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