Wood is used as a major material for buildings and furniture from many centuries because of its vast availability in nature and the ease it can be worked out. It is an excellent insulator and also renewable material. Only about 100 species are used commercially as building materials although thousands of different species exist. Wood is organic, renewable, biodegradable, and recyclable.
Types of Wood Species – Hardwood and Softwood
Timber is one of the important materials used in the construction industry because of its versatility, diversity, and aesthetic properties. Forests are divided as Hardwoods in temperate and tropical climates and Softwoods in temperate and colder climates.
Hardwoods come from brad-leafed or deciduous trees that loose their leaves in the winter, such as oak, maple and walnut. Hardwoods generally have a finer grain and are used in interior trim, paneling surfaces, furniture and flooring.
- Ash wood
Softwoods come from evergreen or coniferous trees that keep their leaves or needles throughout the year. These include
- Western Red Cedar
- Redwood varieties.
A brief about different types of species-hardwoods and softwoods are listed here –https://thearchspace.com/types-of-wood-species-hardwoods-and-softwoods/
Deterioration of Timber
The main causes of deterioration of Timber are
- Weathering – Prolonged exposure to sunlight, rain, and wind, etc. timbers loose their color and turn grey.
- Fungi – Are simple plants ,spreads in wood and decays it.
- Moulds and stains
- Wet and Dry rots
- Insects – Beetles, Termites
Trees require less energy for conversion to timber and in their production when compared to other materials such as brick, steel, and aluminum. Timber is a rapidly renewable material and is environmental issues raised can be greatly reduced by following sustainable forest and production methods, timber certification methods, etc.
The physical properties of the timber can be modified to produce
- Thermal modified timber (by thermal treatment)
- Chemical modified timber ( by reagent treatment )
Types of Wood Products
Wood is layered in various ways to achieve different products with distinct strengths and appearances.
- Laminated Timber
- Structural Insulated Panels
- Composite board
- Wood wool slabs
- It constitutes of layers of dimensional lumber bonded together with resin adhesives. These adhesives have to be durable and moisture resistant to achieve better quality.
- It is a type of Engineered wood.
- Standard-size straight sections (315 × 65 and90 mm; 405 × 90 and 115 mm; 495 × 115 mm)
Cross-laminated timber (CL) – Cross-laminated timber is similar to conventional plywood, except that the laminates are thicker, and the panel thicknesses are generally between 50 and 300 mm.
Laminated Veneer Lumber – manufactured to three grades by laminating timber strands with polyurethane resin under heat and pressure/3 mm thick timber strands or sheets of veneer are coated with waterproof
adhesive and bundled together.
Structural Insulated Panels
- They are used for load-bearing internal and external walls and roofs.
- These are prefabricated lightweight building component panels that support vertical and horizontal loads without internal studding.
- The three panels are bonded together with high density layers (Oriented Strand Boards, Cement Bonded Particle board/ Gypsum based products) on outer layers (face) with insulating layer (rigid cellular foam) in the center(core).
- Structural insulated panels offer a thermally efficient and air-tight form of construction and reduces energy waste in new buildings.
- Veneers are thin sheets of wood sliced from a log; these vary from paper thin slices to 3mm thick.
- Veneers are taken from logs by rotary cutting, slicing with a knife, or sawing.
- Plywood is a laminated or layered wood panel composed of veneers or wood plies, the grains running at right angles to each other.
- It is widely used because of its strength, versality and visual properties.
- Most plywood is manufactured as three, five, or seven plies, depending on the panel thickness.
- Plywood panels are made with various wood species and range from 3mm thick to 28mm thick.
- These panels are produced with three basic core types: wood veneers, lumber cores, and particle board.
- Panels are commonly 4′ in width and lengths vary, most common being 8′,9′,10′.
Blockboard and Laminboard
The standard core plywood products are Blockboard and Laminboard. In both softwood strips are sandwiched between one or two plies.
In blockboard the core strips are between 7 and 30 mm wide, whereas In laminboard, they are below 7 mm in width and continuously glued throughout.
- Particle board is made from wood particles, such as sawdust, sawmill shavings, and wood chips bound together under heat and pressure with some form of glue/resin.
Wood Particleboard (Chipboard)
Wood particleboard (chipboard) is manufactured from wood waste or forest thinning’s which are converted into wood chips, dried and graded according to size. The chips are coated with adhesive to approximately 8% by weight and then formed into board.
Cement-bonded particleboard is manufactured from a mixture of wood particles and cement. It is resistant to fire, water, fungal attack, insects, and frost.
These boards have good sound – insulating properties.
Uses – Soffits, external sheathing and roofing, flooring
Oriented strand board
Oriented strand board (OSB) is manufactured from 0.5 mm thick timber flakes(tangentially cut and measuring approximately 75 × 35 mm),coated with wax and resin, this mix is laid in three layers with the strands running parallel to the sheet on the outer faces and across or randomly within the middle layer. They are cured under heat and pressure, sanded and packed.
It is sometimes called waferboard, because of its rougher finish,
Uses – sheathing in Timber framed houses, roof sharking, flat roof decking, web-material in timber I-beams.
Flaxboard is manufactured from a mixture of at least 70% flax shives (thin slices) and adhesive.
- Fibreboards are manufactured from wood or other plant fibres by the application of heat and/or pressure.
- Medium-density fiberboard(MDF) is denser than plywood and made with wood fibers and binders to form panels denser and stronger than particleboard. There are four grades of MDF, ranging from very high density to low density.
- Hardboard is a very dense fiberboard, similar to MDF, but often produced with one or two very smooth faces.
- Tempered hardboard, Medium board and softboard are other different types of hardboards.
- Wood particles and glue of varying types forms Composite board. It includes hardboard(MDF), particleboard, and waferboard.
Wood Wool Slabs
- Wood wool slabs are manufactured by compressing long strands of chemically stabilized wood fibers coated in Portland cement.
- Resistance to fungal attack.
- Good sound-absorbing properties
- Uses – Partition walls, ceilings, internal walls, permanent concrete shuttering
Types of Wood finishes
Most woods need a protective treatment or finish to protect from moisture content fluctuations and to retain their beauty. Finishes can vary from a high gloss to a satin or matte appearance. Finishes can be opaque or transparent, colored or colorless, penetrate or remain on the surface.
- Glossy finishes are harder and reflect more light.
- Matte finishes produce a soft glow of surrounding light and show the beauty of the surface sheen and wood.
Common paints and finishes
- Water based synthetic resin, quick drying, durable, cleans up with soap and water.
- Uses : Wood siding and trim, cabinetry, combined with latex for more durable latex coating.
- Oil modified resin, most popular paint vehicle, dries faster than oils, hard, clean up with mineral spirits.
- Uses : Exterior and interior primers; wood, brick, metal, combined with enamel, oil, and silicone paints.
- Pigments mixed with varnish,lacquer,or alkyds;durable;clean up with mineral spirits.
- Uses: furniture,floors,metal
- Resin materials produced as a paint or as a two component mix(base and catalyst);hard, dense, film; clean up with special solvents.
- Uses : Tough finishes on most surfaces,waterproof
- Nitrocellulose or acrylic resin based; fast drying; durable film finish; clear or pigmented; clean up with solvents.
- Used for furniture, cabinetry
- Water based; not as scrubbable as acrylics or alkyds-but can be produced with these and enamel for tougher coatings; clean up with soap and water.
- Used for Wallboard, plaster, masonry, acoustic tile.
- Synthetic resins; often called polyurethanes; very tough, durable; pigmented or clear; clean up with solvents; similar to epoxy.
- Used for Interior and exterior wood, wood floors, furniture.
- Synthetic compounds of polyesters, vinyl’s, polyurethanes; durable; resistant to abrasion; excellent flexibility; often factory applied.
- Used for furniture, wood paneling
- Resins dissolved in alcohol or oil; clear or pigmented; tough, hard film; moisture resistant; mixed with epoxy, polyurethane, and others for very tough coating, such as spar varnish; clean with mineral spirits.
- Used for wood products, furniture.
- Made as lac resins in alcohol; dries quicker than varnish, but less durable; affected by heat, moisture, alcohol; clean up with solvents.
- Clear finish coats on wood; mostly used as undercoat and sealing of stains before overpainting.
- Thin water or oil liquids with a colorant; brushed, rubbed or sprayed; sealed over with other finishes or mixed integrally; made as solid body or transparent.
- Used for wood building products; furniture.
- Made as clear or staining as paste or liquid; used alone or over varnish, oil, stain; requires periodic renewal; most not resistant to heat or water.
- Used as wood finishes; furniture; walls; floors.