ALUMINUM AND VINYL SIDING
Aluminum siding finishes will eventually
break down, like the finish on your automobile. When this surface becomes
chalky, it should be cleaned thoroughly and top quality acrylic latex house
paint applied.
Vinyl siding should weather at least eight
years before painting with a top quality acrylic house paint. Do not use
a darker color than the original siding or the siding will expand and buckle
from the additional heat absorbed by the darker siding from the suns rays.
WOOD SHAKES AND SHINGLES
Edge grain heartwood cedar shingles/shakes
are preferred over flat grain and/or second growth timber products. Moss,
algae and lichens must be removed and controlled. Clear water-repellents
may be used, but have a very short lifespan. Roofs should never be coated
with a continuous film coating since these tend to trap mois-ture which
leads to early coating failure and promotes decay. Semi-penetrating stains
are recommended for roof surfaces, but light colors may discolor from water
soluble extractives in the cedar. Sid-ing shakes or shingles may be coated
with either penetrating or solid color stains. Dipping is the preferred
application method to protect the backs of the shingles from moisture collection.
If this is not practical, brushing is the next best application procedure.
FACTORS AFFECTING COATINGS PERFORMANCE
Semi- penetrating stains
These products are almost exclusively alkyd/
oil based to achieve maximum penetration into the wood. Latex products
do not pene-trate as well. Because there is very little surface film to
resist sun-light and moisture, the lifespan of these products is relatively
short. However, a reasonably transparent appearance may be maintained,
and the lifespan lengthened considerably if two coats are applied together,
e.g., apply the second coat while the first coat is still wet. This will
effectively double the lifespan before recoating is required, and is particularly
effective on roughhewn or weathered siding. One coat of semi-penetrating
stain on smooth siding will usually have to be recoated in two to three
years. The second coat will last considerably longer, however. The two
coat application method on roughhewn or weathered wood may last up to six
years depending on the degree of exposure. On horizontal surfaces, such
as decks, one coat is recommended. The life span is further shortened by
abrasion from foot traffic. However, recoating and the blending in of worn
areas is usually not too difficult. If the wood is weathered somewhat to
reduce the mill glaze and increase porosity, one coat of stain will last
longer owing to deeper penetration.
Heavy bodied and solid color stains
These products are available in alkyd/oil
and latex types. They are classified as continuous film coatings since
they resemble a paint film although they are somewhat thinner. Because
they produce more surface film than semi-penetrating stains, they have
more re-sistance to sunlight and weather and have a longer lifespan. Acrylic
latex stains have better color retention than alkyd/ oil stains (are less
apt to fade) and to have a somewhat longer Iifespan. While they obscure
the grain pattern of the wood, they allow the surface texture to remain,
and both are extremely popular finishes for roughhewn siding. Neither product
fares very well over smooth, flat grain surfaces, however.
Exposure
The most severe exposure to sunlight and moisture
(rain, snow and dew) are usually the south and west sides of a structure.
Over-hangs, shade trees and porch enclosures will lessen exposure, and
somewhat protected areas will not have to be recoated as frequently. If,
in the case of paint, it is not practical to apply two topcoats at the
onset to the entire structure, two coats may be applied at least to the
areas experiencing the greatest exposure. Obviously, the greater, more
severe the exposure, the shorter the lifespan of the product. |
Paints
Latex paints, especially the acrylics, compared
to alkyd products, are more flexible, erode at a lesser rate, have better
fade resistance, and are less prone to blister from moisture vapor pressure
(they allow vapor to pass through from inside to outside more readily).
As a result they have a longer lifespan than alkyd products. This lifespan
can be increased dramatically, often doubled, if two finish coats are applied
at the onset, compared to one coat. This procedure is not recommended for
alkyd products, however, since excessive film-build creates a more brittle
coating more prone to check, crack and eventually peel.
To control the leaching of water soluble
extractives (from cedar and redwood) a coat of oil base primer on an acrylic
stain blocking primer and two acrylic latex topcoats is the recommended
procedure over new siding. When applied to the correct surface, the lifespan
of paint is greater than that of stain because the thicker film resists
sunlight and moisture better, and takes longer to erode before recoating
is required.
Surface preparation and application
The longevity of any top coating product is
directly linked to the quality of the product, the quality of the surface
preparation and application technique. Painting or staining over a poorly
prepared surface will certainly cause early product failure. Poor applicator
tools will leave weak spots in the coating film which contribute to early
film breakdown.
Proper application requires the coating
to be distributed evenly over the surface, at the proper spreading rate
(the number of square feet per gallon coverage) indicated on the product
label. Uneven application will become apparent after the coating weathers
for a period, and the undercoat or substrate color begins to show through
in small patches here and there. Stretching the product too far, e.g.,
exceeding the square foot coverage intended for the product, will reduce
the lifespan of the product dramatically.
Product quality
There are two basic ways manufacturers may
reduce the costs of their products to create more profit, or meet lower
competitive price situations. They can use less expensive, lower performance
chemical ingredients or they can use quality ingredients, but use lesser
quantities of these or blend them with lesser quality chemicals. In either
case, product performance will be reduced, resulting in earlier product
deterioration. This not only raises the annual maintenance cost considerably,
in labor and materials, but can cause excessive problems in repairing or
removing the coating prior to the application of the next coat. In some
cases, a brand's "best" product may be decidedly inferior to another brand's
standard product. Product lifespan guarantees are often little more than
marketing tactics, since no manufacturer can be certain of the exposure
the product will be subjected to, or the quality of the surface preparation
and application. They have relatively little cost in replacing the product
compared to the labor involved in repairing or recoating.
Products manufactured and marketed for
low competitive prices may be much more expensive in the long run than
products made for performance.
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