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4 i m p o r t a n t
e x t e r i o r f i n i s h t i p s
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Apply finishes on windless
days. Temperature should be between 50 and 70 degrees fahrenheit.
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Surfaces should be clean and
dry.
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New structures built with
unseasoned wood should air-dry once a month before finishing.
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Back-priming is recommended
for all exterior finishes, particularly paints.
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Don’t use wire brushes or
steel wool as metal particles may become embedded in the wood and can cause
stains. Use stiff bristle brushes.
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Use finishes recommended for
wood exteriors.
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Follow manufacturer’s
directions and read warnings on toxicity.
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Don’t mix incompatible
materials together. Finished failures may result from mixing incompatible products or
applying them over one another.
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Moisture is the most common
cause of finish failures, so use proper vapor barriers, air vents, and
flashing in new construction.
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Saw-textured redwood holds
stains, water repellents and bleaches up to twice as long as smooth-surfaced
wood.
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Redwood grades marked
'Certified Kiln Dried' will provide the best finish retention available.
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To avoid nail stains, use
stainless steel, aluminum or top quality, hot-dipped galvanized nails.
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Periodic rinsing with a
garden hose will remove dirt and grime from the siding. Stubborn build-up can be
removed by scrubbing with a bristled brush with a solution of warm water and
a mild detergent. Rinse afterward.
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Splash lines can be
minimized by an occasional hosing of the unaffected area, which will even
the appearance of the wood.
e x t e r i
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Varnishes and polyurethanes
crack and peel when used for exteriors. They are difficult and expensive to
apply and deteriorate quickly.
Oil treatments will attract
dirt, and are highly susceptible to mildew and will darken the wood.
"Shake and shingle"
type paints do not last well on cedar wood siding.
f i n i s h
r e s t o r a t i o n
Dirt and dust may build up to
the point that a mere rinsing with water from a hose will not remove them. A
mild detergent and warm water will generally remove stubborn dirt and grime.
Mildew appears as dark spots or
gray, fan shaped spots on the wood surface. Severely infested areas may appear
uniformly gray or black. To remove a mild case of mildew, scrub with a mild
cleanser or detergent. Next rinse with a household bleach to kill surviving
spores. Lastly, rinse with water. When applying a new finish, be sure it
contains a mildew-cide. Note: Household bleach should never be mixed with
detergent containing ammonia. Fumes can be fatal.
For severe mildew infestations,
scrub with a stiff bristle brush using a solution of one cup of tri-sodium
phosphate, one cup of liquid household bleach and one gallon of warm water.
Rinse thoroughly. If necessary, follow with an application of 4 ounces of oxalic
acid crystals dissolved in one gallon of warm water in a non-metallic container.
Apply evenly with a soft brush. When wood dries, rinse with water. Caution:
Oxalic acid is poisonous, but not dangerous if precautions are taken. Wear
rubber gloves and avoid contact with skin or eyes.
Nail
stains are a problem that can be avoided by using stainless
steel, aluminum or top quality, hot-dipped galvanized nails. The cleaning method
described above for removing heavy mildew stains is suggested for nail stains.
To help prevent recurrence, countersink the nails and swab the holes with a
water repellent. When dry, fill the nail holes with a non-oily wood filler for
natural finishes, or putty if the wood is to be painted.
Paint peeling, blistering, and
flaking occurs when moisture under a non-breathing film finish destroys the
film’s adhesion to the wood. A properly installed vapor barrier is recommended to control this problem. Vapor barriers should be on the warm
side of the wall. Problems also may be caused by faulty surface preparation, or
the use of incompatible materials.
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Discoloration of paints and
finishes may occur when extractives are dissolved in water and leach from the
wood. This discoloration can also result from moisture migrating to the surface
of unseasoned lumber. To remove extractive stains and to restore the new
appearance to weathered wood, follow these steps. Scrub wood with a bristle
brush and a solution of one cup tri-sodium phosphate (TSP) and one cup of
household bleach to a gallon of water. Then apply a solution of 4 ounces oxalic
acid crystals dissolved in one gallon of warm water. When wood dries, rinse
thoroughly with water.
r e m o v i
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When a finish has deteriorated
to the point of cracking and peeling or some other finish ailment, it may
necessary to remove it before refinishing.
Sanding effectively removes
pigmented stain finishes. Galvanized nail heads should be set below the surface
before sanding to protect the coating and prevent nail stains.
Water blasting is an effective
way of removing old finishes and grime and preparing for a new finish. A fine,
high-powered spray effectively removes loose materials without damaging the
wood.
The use of a paint and varnish
remover is another way to remove a finish. Several kinds are available. Before
using, test the preparation on a piece of new, clean, redwood to make sure it
will not discolor the wood, particularly if a natural finish is to be used.
Film-forming finishes can be removed with a paint and varnish remover. Heat is
another method of paint removal.
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