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Exterior Finishes & Siding: Cellular PVC Lumber
Cellular PVC Lumber
Imagine intricate exterior detailing that keeps its shape and never
needs painting. Cellular PVC is a solid, extruded material that has the
working characteristics of wood, and is used for interior trim,
exterior trim, and paneling as well as windows and doors, blinds, and
furniture.
Details
PVC (polyvinyl chloride) lumber is manufactured in interior grade,
exterior grade, and cellular form. Cellular PVC is created by celuka, a
foaming extrusion process than creates tiny air bubbles within the
shape, resulting in a density less than half that of regular PVC. The
material is then cooled to form a smooth, hard skin that doesn't absorb
paint or bleed. Cellular PVC has a tensile strength of 2,000 to 5,000
psi, resists deflection up to 150F, and has a low coefficient of
thermal expansion. It weighs about the same as softwood.
Cellular PVC is medium white. Boards are delivered 4' x 18' and 4' x
20', then cut up and sanded. Standard wood trim dimensions and profiles
are available up to 11 1/4" x 1 3/8", and as thin as 3/8". Boards can
be produced in any length, but 18' is most commonly in stock. Custom
profiles can be extruded.
Installation
Profiles can be welded like vinyl, or cut, milled and fastened like
wood. A carbide blade is recommended, with milling and drilling at
slower speeds to avoid excess heat. Bevel and caulk joints to allow for
slight thermal expansion. Light-colored acrylic paint can be used.
Benefits/Costs
Cellular PVC avoids many potential problems of wood, such as rot,
split, water absorption, peeling paint, and termites. It can be left
unfinished, or with a color-matched permanent finish. At approximately
$3 per lineal foot, cellular PVC costs less than redwood or cedar, but
more than finger-jointed pine, which ranges between $2 and $2.50 per
foot. Limited warranties vary from 10 to 20 years.
Limitations
Cellular PVC becomes brittle below 40F, requiring pre-drilling before
cold weather installation, especially near edges. Residue builds up if
the sander is allowed to get too hot. Cellular PVC is considered too
expensive for siding, and is not structural for uses such as decking.
Code/Regulatory
Cellular PVC has been ASTM tested for a wide range of properties.
Results are available from manufacturers. Flame spread is 46,
self-extinguishing when flame source is removed.
Availability
PVC is stocked by lumber dealers. Custom profiles will take about two weeks.
Disclaimer: The information on the system, product or material
presented herein is provided for informational purposes only. Courtesy of toolbase
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