Structural Materials Used in D&T |
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| Material | Physical Properties | Chemical Properties |
Carbon steels |
The higher carbon content enables carbon to harden and toughen these steels. |
Low carbon manganese and vanadium alloy steels are the most common steels used in structures.
Mild steel is approx. 99.75 % iron with up to 0.25% carbon. Carbon steels contain up to 1.5% carbon. Carbon steels may be hardened and tempered. Alloy steels contain other elements that improve the steels properties:
Steel will rust in the presence of both water and air. In order to prevent rusting, water or air, or preferably both, must be prevented from reaching the surface of the metal. This can by done by applying a surface covering that will prevent water and air from reaching the steel. A protective surface covering may be applied by painting, lacquering, oiling, plastic coating, electroplating, galvanising or enamelling. |
Steel pipe |
Round mild steel tube, lighter than solid steel. Strong in compression and tension, resistant to bending. |
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Steel box section (square) |
Square mild steel box section / hollow section, lighter than solid bar. Strong in compression and tension, resistant to bending. |
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Steel box section (rectangular) |
Rectangular mild steel box section / hollow section, lighter than solid bar. Strong in compression and tension, resistant to bending. |
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Steel channel |
U section mild steel bar. Strong in compression and tension, resistant to bending. |
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Steel T bar |
T section mild steel bar. Strong in compression and tension, resistant to bending. |
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Rolled Steel Joist (RSJ) |
Rolled Steel Joist (RSJ) is an H section mild steel bar that is strong in compression and tension, and is resistant to bending. |
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Steel angle bar |
L section mild steel bar. Strong in compression and tension, resistant to bending although only having two sides, is the weakest of the structural sections. |
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Steel flat bar |
Mild steel flat bar will bend fairly easily on the flat side but is resistant to bending on its edge. |
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Steel round bar. |
Mild steel, carbon steel and alloy steel round bars are strong in all directions. Textured steel round bar is used for reinforcing concrete. |
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Aluminium alloy pipe (round tube) |
Good strength, light weight, corrosion resistant (after formation of dense oxide layer) Can be cast, extruded, welded, anodised. |
Aluminium alloys containing magnesium, manganese and/or silicon are used in structures. |
Aluminium alloy (other sections) |
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Beech (hardwood) |
Straight, close grained timber, stable, quite hard, does not warp easily. Used for tools such as wood planes, mallets. Widely used for furniture because of its strength and stability. |
Hydrocarbon. Can burn. Will rot if left unprotected for long periods. Needs to be painted or varnished. |
Oak (hardwood) |
Very tough timber, used for timber frames of buildings, doors, door and window frames. |
Hydrocarbon. Can burn.
Will rot if left unprotected for long periods. Needs to be painted or varnished. It is an acidic wood that attacks steel screws and fittings leaving black stains on the wood. Only brass or bronze screws, hinges and other fittings should be used |
Ash (hardwood) |
A tough timber capable of withstanding shocks, used for some hammer and axe handles. |
Hydrocarbon.
Can burn. Will rot if left unprotected for long periods. Needs to be painted or varnished. |
Teak (hardwood) |
Very heavy, stable timber.
The best teaks such as Burmese teak are very oily, very dense, hard and tough. Because of the high oil content, teak is difficult to glue but it has excellent weathering qualities. The most expensive yachts have untreated teak decks that are completely exposed to salt water and the elements without any detrimental effect on the timber. Teak is also widely used for making good quality garden furniture. |
Hydrocarbon. Can burn.
High oil content in teak gives it excellent weathering qualities. It is an acidic wood that attacks steel screws and fittings leaving black stains on the wood. Only brass or bronze screws, hinges and other fittings should be used. |
Iroko (hardwood) |
Has similar look to teak but is much more prone to twist and bend.
Very good weathering qualities, will go grey if left untreated. Brass or bronze fittings must be used or staining will occur. |
Hydrocarbon. Can burn.
Will discolour if left unprotected for long periods. Needs to be painted or varnished. It is an acidic wood that attacks steel screws and fittings leaving black stains on the wood. Only brass or bronze screws, hinges and other fittings should be used |
Mahogany (hardwood) |
Easy to cut, shape and plane but some interlocking or reverse grain may make it difficult to get a good finish. |
Hydrocarbon. Can burn. Will rot if left unprotected for long periods. Needs to be painted or varnished. |
Walnut (hardwood) |
A fairly hard wood that's moderately durable.
It can be worked easily with both hand and machine tools. It is used for furniture, carving, turned work and to make decorative veneers. |
Hydrocarbon. Can burn.
Will rot if left unprotected for long periods. Needs to be painted or varnished.
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Douglas fir (softwood) |
Douglas Fir is a beautiful, light pinkish coloured wood with few knots. It has a straight grain that makes the timber less likely to twist and warp. It is used for floors, panels, mouldings and construction jobs in general. |
Hydrocarbon. Can burn.
Will rot if left unprotected for long periods. Needs to be painted or varnished. Can be coloured using wood stains. |
Western red cedar (softwood) |
Western Red Cedar is a light, uniformly textured, straight-grained timber that contains no resin.
Western Red Cedar is easy to work and is a favourite material of architects and builders. The timber contains natural preservatives that make the timber suitable for outdoor use. It is fairly stable and less likely to warp and twist than other softwoods. |
Hydrocarbon. Can burn.
Will rot if left unprotected for long periods. Needs to be painted or varnished. Can be coloured using wood stains. |
Parana Pine (softwood) |
Attractive honey coloured wood with straight grain. Medium strength, low resistance to rotting.
Used for staircases, doors, window frames, furniture and general construction. Holds nails and screws well. |
Hydrocarbon. Can burn.
Will rot if left unprotected for long periods. Needs to be painted or varnished. Can be coloured using wood stains. |
Larch |
Larch is a tough, long lasting timber, rich in resin. The high resin content inhibits mould and fungal growth which makes it suitable for humid or damp conditions. Ideal for all sorts of construction work |
Hydrocarbon. Can burn.
Must be painted or varnished to prevent rotting but the high resin content makes it a long lasting timber suited to humid conditions. Can be coloured using wood stains. |
Sitka spruce (softwood) |
Sitka spruce has straight grain, with a uniform texture and a high strength to weight ratio. It is the timber used for making yacht masts and spars and for making musical instruments such as violins and acoustic guitars.
It is relatively soft and does not hold screws well. It is also prone to rot, so is used mainly for internal joinery. |
Hydrocarbon. Can burn.
Will rot if left unprotected for long periods. Needs to be painted or varnished. Can be coloured using wood stains. |
Hemlock |
Straight grain, stable timber used for doors, door frames, furniture and general construction. Holds nails and screws well. |
Hydrocarbon. Can burn.
Will rot if left unprotected for long periods. Needs to be painted or varnished. Can be coloured using wood stains. |
Plywood |
Plywood is a structurally stable in dry conditions board because of the way the plies are laid but will twist and warp if left unsupported in damp or wet conditions.
Board thicknesses range from about 2mm to above 25mm but the most commonly used are 6 -18mm. Plywood boards are usually sold in sizes of 2440 x 1220mm. The quality and thickness of the plies varies according to the quality of the board. Boards may have one good face or two good faces. The best quality boards are marine grade plywood that has good quality faces and inner veneers and is bonded with waterproof adhesive. |
Hydrocarbon. Can burn.
Will delaminate and rot if left unprotected for long periods. Needs to be painted or varnished. Can be coloured using wood stains. |
Blockboard and laminboard |
Block and laminboard consist of battens with at least two layers of veneers on each side of the board, encasing the battens.
Board thicknesses range from about 9mm to above 25mm and in sizes of 2440 x 1220mm. It is a strong board that is sometimes used as a cheaper alternative to plywood. It is not suitable for exterior use without the board being thoroughly sealed against the weather. Structurally stable board in dry conditions. |
Hydrocarbon. Can burn.
Will delaminate and rot if left unprotected from the elements. Needs to be painted or varnished. Can be coloured using wood stains. |
Chipboard |
An interior grade board made from tiny wood chips bonded with adhesive under heat and pressure.
Chipboard is usually sold in sizes of 2440 x 1220mm and is available in various thicknesses. Thick boards with a thermoplastic laminate are used as kitchen work tops. Structurally stable board in dry conditions. |
Hydrocarbon. Can burn.
Will delaminate and rot if left unprotected from the elements. Needs to be painted or varnished.
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MDF |
An interior grade board made from tiny wood fibres bonded with adhesive under heat and pressure.
Medium Density Fibreboard (MDF) is usually sold in sizes of 2440 x 1220mm and is available in various thicknesses. It can be easily machined leaving a smooth surface that takes paint and stains readily. Structurally stable board in dry conditions. |
Hydrocarbon. Can burn.
Will delaminate and rot if left unprotected from the elements. Needs to be painted or varnished.
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Hardboard |
Hardboard is an interior grade board made from tiny wood fibres bonded with adhesive under heat and pressure.
It is a cheaper alternative to Medium Density Fibreboard (MDF). It is usually sold in sizes of 2440 x 1220mm and is available in various thicknesses up to about 6mm. Structurally stable board in dry conditions. |
Hydrocarbon. Can burn.
Will delaminate and rot if left unprotected from the elements. Needs to be painted or varnished.
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Polycarbonate sheet |
Polycarbonate sheets are hollow sections having 2 or 3 layers. It is generally used as a roofing material, particularly for conservatories.
Very strong, light weight, transparent material. |
Thermoplastic. |
Glass reinforced plastic (GRP) |
Polyester resin reinforced with glass fibres, strands or mats can be formed into any shape giving a strong shell structure.
Structural strength can be improved by increasing the number of layers of fibre glass, changing the reinforcing material to something stronger and bonding frames and stringers to a GRP shell structure. |
Thermoset |
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