Definition
Fiber cement is a composite material made of sand, cement and cellulose fibers. Fiber cement siding comes in various forms but is often seen in horizontal boards, imitating wooden clapboard and in sheet form. Other formats include imitation shingles. Fiber cement siding can be used to cover the exterior of a house and can also be used as a substitute for timber fascias and barge boards in high fire danger areas. It is also commonly applied as a tile underlay on decks and in bathrooms and is also easy to secure and maintain as a soffit/eave lining.
Specifications
Fiber cement sheeting products are manufactured by James Hardie and CertainTeed Corporation, and customized by suppliers such as Unicrete Products Ltd.
Fiber cement sheets come in a variety of thicknesses (between 1/4- to 5/16-inch) and densities. A lower density resulting in a fibrous rough edge when cut and a higher density having a cleaner smoother edge when cut. Thermal resistance and sound transmission vary great between fiber cement products. Fiber cement sheet products rate poorly in thermal resistance and sound transmission and separate wall insulation is highly recommended. Generally the thicker and more dense the product the better resistance it will have to temperature and sound transmission.
Construction techniques
Fiber cement sheets are usually delivered on-site by truck but on properties with difficult access – for example steep waterfront properties – the product is often delivered by water barge then craned onto site. Fiber cement sheeting is a very heavy product and requires 2 men to carry the uncut sheets to their cutting location.
Once the product is cut it requires again 2 men to install – one to hold the sheet flush against studwork and the other to nail the product in place. Once the product is fixed the joins are covered with timber battens and the entire wall surface is painted. FC sheets can be cut to size in three ways:
- Thinner sheets can be scored with a heavy duty cutting blade and snapped
- Purpose made Fibro cutter
- Thicker and more dense sheets require cutting by a mechanical saw
Wall Preparation
- Fiber cement sheets can be installed over existing sheathing, depending on the condition of the existing material.
- The application of a foil insulation product is recommended before applying fiber cement sheets directly to studs or over existing materials.
- Proper sheathing should be applied before fiber cement sheets are installed; plywood, builder board or foam-type sheathings are all acceptable.
Painting
- Only 100% acrylic latex paint should be used.
- NEVER use oil-based paints.
- Solid or semi-transparent stains should be used only on unprimed sheets.
- The lifespan of paint on fiber cement sheets is significantly longer than on hardwood and wood sheeting.
Alternatives
Alternatives to fiber cement siding include vinyl/PVC, wood and wood composite products and aluminum. Advantages of vinyl include the fact that it has a lower material cost and is easier to transport than fiber cement siding due to its lighter weight and its pliability. Vinyl siding, however, is more susceptible to fire damage (or melting under extreme temperatures) than fiber cement siding, and can become brittle in cold weather or from long-term solar exposure. Fiber cement siding primary advantage over wooden siding is its lack of susceptibility to termites or rot.
