Siding is the outer covering or cladding of a house meant to shed water and protect from the effects of weather. On a building that uses siding, it may act as a key element in the aesthetic beauty of the structure and directly impact its property value.
Siding may be formed of horizontal boards or vertical boards (known as weatherboarding in many countries), shingles, or sheet materials. In all four cases, avoiding wind and rain infiltration through the joints is a major challenge, met by overlapping, by covering or sealing the joint, or by creating an interlocking joint such as a tongue-and-groove or rabbet. Since building materials expand and contract with changing temperature and humidity, it is not practical to make rigid joints between the siding elements.
Siding may be made of wood, metal, plastic (vinyl), masonry , or composite materials. It may be attached directly to the building structure (studs in the case of wood construction), or to an intermediate layer of horizontal planks called sheathing.
Wood siding in overlapping horizontal rows or "courses" is called clapboard. In colonial times, Eastern white pine was the most common material. Wood siding can also be made of naturally weather-resistant woods such as redwood or cedar. Jointed horizontal siding may be shiplapped.
Plywood sheet siding is sometimes used on inexpensive buildings, sometimes with grooves to imitate vertical shiplap siding. (One example of such grooved plywood siding is the type called T1-11 ["tee-one-eleven"—often written T111 ].)
Wood siding is very versatile in style and can be used on a wide variety of homes in any color palette desired.
Though installation and repair is relatively simple, wood siding requires more maintenance than other popular solutions, requiring treatment every four to nine years depending on the severity of the elements to which it is exposed. Ants and termites are a threat to many types of wood siding, such that extra treatment and maintenance that can significantly increase the cost in some pest-infested areas.
Wood is a moderately renewable resource and is biodegradable. However, most paints and stains used to treat wood are not environmentally friendly and can be toxic. Wood siding can provide minimal insulation and structural support compared to thinner cladding materials.
Wood clapboard is often imitated using vinyl siding or uPVC weatherboarding. It is usually produced in units twice as high as clapboard. Plastic imitations of wood shingle and wood shakes also exist. Vinyl or plastic siding has grown in popularity due to the generally low maintenance and low cost appeal it offers.
Since plastic siding is a manufactured product, it may come in limited color choices. Historically vinyl sidings would fade, crack and buckle over time, requiring the siding to be replaced. However, newer vinyl options have improved and resist damage and wear better. Vinyl siding is sensitive to direct heat from grills, barbecues or other sources. Unlike wood, vinyl siding does not provide additional insulation for the building, unless an insulation material (e.g. foam) has been added to the product.
An environmental benefit of vinyl siding is that its production does not require the consumption of certain natural resources that other types of siding would require, such as trees, aluminum, or stone. (It does, however, require petroleum.) An environmental cost of vinyl siding is that it is difficult to dispose of responsibly. It cannot be burned (due to toxic dioxin gases that would be released) and currently it is not recycled.
Products provide environmental advantages by reducing energy use by up 20 percent. On average, insulated siding products have an R-value of 3.96, triple that of other exterior cladding materials. Insulated siding products are typically ENERGY STAR qualified, engineered in compliance with environmental standards set by the U.S. Department of Energy and the EPA.
In addition to reducing energy consumption, insulated siding is a durable exterior product, designed to last more than 50 years, according to manufacturers. The foam provides rigidity for a more ding- and wind-resistant siding, maintaining a quality look for the life of the products. The foam backing also creates straighter lines when hung, providing a look more like that of wood siding, while remaining low maintenance.
Manufacturers report that insulated siding is permeable or “breathable,” allowing water vapor to escape, which can protect against rot, mold and mildew, and help maintain healthy indoor air quality.
Metal siding comes in a variety of metals, styles, and colors. It is most often associated with modern, industrial, and retro buildings. Utilitarian buildings often use corrugated galvanized steel sheet siding or cladding, which often has a coloured vinyl finish. Corrugated aluminium cladding is also common where a more durable finish is required.
Formerly, imitation wood clapboard was made of aluminum (aluminum siding). That role is typically played by vinyl siding today. Aluminum siding is ideal for homes in coastal areas (with lots of moisture and salt), since aluminum reacts with air to form aluminum oxide, an extremely hard coating that seals the aluminum surface from further degradation. In contrast, steel forms rust, which looks ugly and can weaken the structure of the material, and corrosion-resistant coatings for steel, such as zinc, sometimes fail around the edges as years pass. However, an advantage of steel siding can be its dent-resistance, which is excellent for regions with severe storms—especially if the area is prone to hail.
Despite the drawbacks above, metal siding:
Masonry sidings are varied (brick, stone, stucco) and can accommodate a variety of styles--from formal to rustic. Though masonry can be painted or tinted to match many color palettes, it is most suited to neutral earth tones. Masonry has excellent durability (100+ years), and minimal maintenance is required. The primary drawback to masonry siding is cost, though some stucco options can be similar to wood siding costs. Precipitation can threaten the structure of buildings, so it is important that the siding will be able to withstand the weather conditions in the local region. For regions that receive a lot of rain, modern stucco mixtures, specifically EIFS (Exterior Insulation and Finish Systems), have been known to suffer underlying wood rot problems with excessive moisture exposure. However, original stucco mixes (cement, lime, sand, and water) and many of the newest synthetic mixes are compatible with moist conditions.
The environmental impact of masonry depends on the type of material used. In general, concrete and concrete based materials are intensive energy materials to produce. However, the long durability and minimal maintenance of masonry sidings mean that less energy is required over the life of the siding.
Various composite materials are also used for siding: asphalt, asbestos, fiber cement, aluminum (ACM) etc. They may be in the form of shingles or boards, in which case they are sometimes called clapboard.
Composite sidings are available in many styles and can mimic the other siding options. Composite materials are ideal for achieving a certain style or 'look' that may not be suited to the local environment (e.g. corrugated aluminum siding in an area prone to severe storms; steel in coastal climates; wood siding in termite-infested regions).
Costs of composites tend to be lower than wood or masonry options, but vary widely as do installation, maintenance and repair requirements. Not surprisingly, the durability and environmental impact of composite sidings depends on the specific materials used in the manufacturing process.