The chief advantages of wood in construction industry include its ease of production and of process by which wood is packaged and transported, its low thermal conductivity, and its strength-to-weight ratio (which is greater than that of cast iron and is identical to that of the stronger concretes) (Rowell 9).
Yet, because of its peculiar weaknesses as an organic material, such as vulnerability to fungi and various insects, its relative lack of versatility in terms of design, and its long-term rise in price in comparison with concrete, the relative role of wood as a building material may to some degree decrease in the future, and further replacement may be projected. If considered as a structural material in large building construction, wood has already been largely replaced by concrete framing, brick or concrete walls, and concrete floors.
This trend will probably continue in the future. On the other part, wood framing probably will retain its dominating position in the residential building, although giving way a bit to steel, concrete, perhaps aluminium, and sandwich panel method of building. The advantages of metal roof frameworks are gradually reducing the amount of wood required for roof structures. Moreover, for exterior trimming wood is being increasingly substituted by brick exterior and by panels of such building materials as asbestos, metal, and organic materials with a polymeric structure.
Dry wall building and the utilisation of gypsum plasterboard and of metal lath are also considerably lessening the need for wood. The most important role for wood is probably in finished flooring, but there are modern trends toward replacement of composition and various types of synthetic materials even in living areas. Wood, like steel, is yielding to aluminum as the leading building material for window frames, door frames, doorways, trim, and other such purposes.
In concrete building the formwork is tending change from wood to steel and plywood and also to plastics. Growing popularity of plywood and of laminated structural members may slow down the trend away from wood. Laminated wood arches, structural frameworks of wood, and roof systems have proved appropriate for spanning distances up to 120 feet, and, because of their attractive and pleasant appearance, are today in frequent use in the building of churches and temples, buildings for public gatherings or meetings, shopping areas, and the similar places.
Plywood, which to some degree possesses more physical strength than lumber, may replace lumber in almost any of its uses; it is already extensively used in subflooring, boarding, interior panelling, concrete forms, and so forth. Thus, it may be expected to grow in total use at almost twice the rate predicted for lumber. Use of concrete in building is constantly increasing today.
It is a changeable mixture of portland cement, fine aggregates (almost always sand), and coarse aggregates (crushed stone, gravel, cinder, slag, or whatever else is available within a particular area). The proportions of these ingredients are influenced by the particular use to which the concrete is to be intended, but they are at most times 1:2:4. As can be seen, cement is the minor component in this mixture.
The fact that concrete is the most extensively used building material can be explained by its advantages related to wood among which are versatility, its high breaking strength relative to bricks and other kinds of masonry materials, the low price which makes it comparatively inexpensive material relative to structural steel, and in essence the presence of concrete components almost in all areas (Classic Encyclopaedia). The main uses of concrete in England are in dams, water tanks, pipes and sewers, heavy walls, piers, caissons, columns, and road and sidewalk pavements.
In addition, concrete is utilised in the form of units cast in a particular form before being used in building, such as concrete blocks and cast stone, whose principal advantage over wood, brick, and structural tile is that they are costing relatively little. Because of the low flexural strength of concrete, it is combined with steel in most of its construction applications (Classic Encyclopaedia). This combination is made possible by the match of coefficients of thermal expansion of these materials.
The amount of reinforcing steel – rods, wire, wire-mesh, and so forth – needed for a concrete structure is only one-third to one-half the amount needed for a similar completely steel structure. In England, the possibilities of this technique of construction are just beginning to extend its use beyond massive complex constructions. The chief disadvantages of reinforced concrete (also known as ferroconcrete or armoured concrete) in comparison with structural steel are the time and costs of construction, even if one takes account of the applying paints to the surface of steel members and their trimming.
It is costly to build and remove forms, shores, and temporary metal or wooden frameworks. Most of the developments, which been made not long ago, in methods of concrete building are somehow related to reducing expense on forms, First, as an alternative to the traditional lumber and plywood, steel – and more recently, plastic with fibrous matter to confer additional strength – forms have been experimented.
Plastics are especially showing great promise, in view of the fact that they are smooth and easily utilised, able to keep water, may be given extraordinary shapes, and may be use again and again from fifteen to twenty times. Second, “slip-form” pavers have been successfully employed in laying road pavements (Green 1-2). Third, precasting of concrete members has been used as a mass production technique and to provide solid and robust in construction, more unchanging in form concrete, but presents some transportation problems.
Fourthly, so-called tilt-up construction and lift-slab construction has permitted walls, floors, and columns to be poured on a horizontal surface and then either tilted or lifted into place. Finally, able to be used more than once, adjustable length steel trusses have removed the need for the multiple strengthening which differently has to be placed under the conventional built-up forms. The faster such form-saving processes are improved and used by engineers and constructors, the faster steel concrete is likely to be used as a structural material.