Factory And Site

In-factory work and on-site work each has its associated set of advantages and disadvantages. An important task of the detailer is to allocate the work of making a building judiciously between the two for optimum construction speed, quality, and cost.

1. In the factory, the weather is always dry and temperatures are always comfortable. Lighting is good, large machines and tools with impressive capabilities and extreme accuracy can be utilized, and workers can work in comfortable postures. Wage rates for factory workers are substantially lower than for on-site workers, and worker productivity (because of the factors mentioned earlier in this paragraph) is higher. But the sizes and weights of the components created by the factory arc restricted by the dimensions and capacities of trucks.

On the jobsite, the weather and the light vary greatly in quality. Tooling is not as sophisticated. Access to the work is not always the best. Wage rates are high and productivity ranges from high to low, depending on weather, light, tooling, and access. But very large assemblies can be created and adjustments can be made to site conditions. Assemblies can be built to actual required size and shape, which is a particular advantage in renovation work.

2. At the scale of a custom-designed house, the optimum mix of factory and site operations is well established. Foundations, framing, roofing, siding, and insulating are done on the site, using simple factory-produced components, such as formwork panels, masonry blocks, dimension lumber, wood panel products, shingles, and insulation batts. Windows and doors, which require high precision and exacting finishes, arc not made on site but are ordered as prefabricated units from factories. Electrical wiring, plumbing, and heating and cooling systems are installed on site, but such exacting components as fixtures, ductwork, furnaces, boilers, convectors, and registers are factorv-made. Finish surfaces j for ceilings, walls, and floors are installed on site, using factory-produced panel products in many cases. Interior doors and cabinetry are made as units in factories and simply nailed or screwed into the house. In general, the smaller, highly precise, highly finished components are made in the factory, while the larger elements of the building are created on site from simple, easily fitted pieces of factory-made materials.

3. In many larger buildings, the choices may not be so obvious. Should a concrete frame be precast or sitecast? Should a building be clad with brickwork or stonework that is assembled on the site, or should it be clad with factory-made panels? Should partitions be constructed on site, or should they be interchangeable prefabricated panels? These are complex choices that involve the entire building design team. ■

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