Mild Typically inland, more than 50 km from the coast and away from industrial areas. This environment has been subdivided as follows: Mild-tropical within the tropical climatic zone (for example, Katherine and Mt Isa). Mild-temperate within the temperate climatic zone (for example, Dubbo and Mildura). Mild-arid within the arid climatic zone (for example, Alice Springs and Kalgoorlie) Design Considerations Brick Technical Manual 58 5.1.2 Masonry units When masonry units absorb moisture containing physical stresses leading to particles being dislodged dissolved salts, damage can result when this moisture from the surface; this is referred to as salt attack. dries out. This damage can effect either the A standard salt cycling test is given in AS/NZS 4456.10 mortar joints (if the mortar is soft) or to the units, and to measure the resistance of masonry units to salt sometimes to both. attack. The available grades, in order of increasing The mechanism operating is that the dissolved salts resistance, are Protected, General Purpose and crystallise just below the surface as the moisture Exposure. evaporates and the growth of the crystals causes

Plans for plumbing systems must usually be approved before construction is started. After installation of the piping and fixtures has been completed, both the new work and any existing work affected by the new work must be inspected and tested. The plumber or plumbing contractor is then informed of any violations. These must be corrected before the governing body will approve the system. Most plumbing codes allow air or water to be used for preliminary testing of drainage, vent, and plumbing pipes. After the fixtures are in place, their traps should be filled with water and a final test made of the complete drainage system. When a system is tested with water, all pipe openings are tightly sealed, except the highest one. The pipes are then filled with water until overflow occurs from the top opening. With this method, either the entire system or sections of it can be tested. In no case, however, should the head of water on a portion being tested be less than 10 ft, except for the top 10 ft of the system. Water should be kept in the system for at least 15 min before the inspection starts. During the inspection, piping and fixtures must be tight at all points; otherwise approval cannot be granted. An air test is made by sealing all pipe outlets and subjecting the piping to an air pressure of 5 psi throughout the system. The system should be tight enough to permit maintaining this pressure for at least 15 min without the addition of any air. The final test required of plumbing systems uses either smoke or peppermint. In the smoke test, all traps are sealed with water and a thick, strong-smelling smoke is injected into the pipes by means of a suitable number of smoke machines. As soon as smoke appears at the roof stack outlets, they should he closed and a pressure equivalent to 1 in of water should be maintained throughout the system for 15 min before inspection begins. For the peppermint test, 2 oz of oil of peppermint are introduced into each line or stack. Natural and manufactured gases are widely used for heating in stoves, water heaters, and space heaters of many designs. Since gas can form explosive mixtures when mixed with air, gas piping must be absolutely tight and free of leaks at all times. Usual plumbing codes cover every phase of gas-piping size, installation, and testing. The local code governing a particular building should be carefully followed during design and installation. (National Fuel Gas Code, ANSI Z223.1, American National Standards Institute and National Fire Protection Association; see also model plumbing codes and mechanical codes of the various building officials associations listed in Art. 14.1.) The usual practice is for the public-service gas company to run its pipes to the exterior wall of a building, terminating with a brass shutoff valve and gas meter. The gas piping from the load side of the meter is generally extended to the inside of the building. From this point, the plumbing contractor or gas-pipe fitter runs lines through the building to the various fixture outlets. When the pressure of the gas supplied by the public-service company is too high for the devices in the building, a pressure-reducing valve can be installed near the point where the line enters the building. This valve is usually supplied by the gas company. Besides municipal codes governing design and installation of gas piping and devices, the gas utility serving the area will usually have a number of regulations that must be followed. Typically, meters are required to be installed outside the building. The gas supply should not enter the building from below grade unless certain venting requirements are met, and gas pressure regulators installed inside the building must be vented to the outdoors. The local authorities and gas utility should be consulted as to special regulations relating to the installation of the gas

The Presence of Sensitive Finishes. Tile or other sensitive finishes are much less tolerant of movements. The Rigidity of the Structure. If a footing beneath part of a very rigid structure settles more than the others, the structure will transfer some of the load away from the footing. However, footings beneath flexible structures must settle much more before any significant load transfer occurs. Therefore, a rigid structure will have less differential settlement than a flexible one. Aesthetic and Serviceability Requirements. The allowable settlement for most structures, especially buildings, will be governed by aesthetic and serviceability requirements, not structural requirements. Unsightly cracks, jamming doors and windows, and other similar problems will develop long before the integrity of the structure is in danger. Another example of allowable settlements for buildings is Table 6.13, where the allowable foundation displacement has been divided into three categories: total settlement, tilting, and differential movement. Table 6.13 indicates that those structures that are more flexible (such as simple steel frame buildings) or have more rigid FIGURE 6.20 Laboratory collapse test results for a silty sand. The soil was loaded in the oedometer to a pressure of 144 kPa and then inundated with distilled water. foundations (such as mat foundations) can sustain larger values of total settlement and differential movement. 6.5.5 Collapsible Soil Collapsible soil can be defined as soil that is susceptible to a large and sudden reduction in volume upon wetting. Collapsible soil usually has a low dry density and low moisture content. Such soil can withstand a large applied vertical stress with a small compression, but then experience much larger settlements after wetting, with no increase in vertical pressure. Collapsible soil falls within the second basic category of settlement, which is settlement of the structure due to secondary influences. In the southwestern United States, collapsible soil is probably the most common cause of settlement. The category of collapsible soil would include the settlement of debris, uncontrolled fill, deep fill, or natural soil, such as alluvium or colluvium. In general, there has been an increase in damage due to collapsible soil, probably because of the lack of available land in many urban areas. This causes development of marginal land, which may contain deposits of dumped fill or deposits of natural collapsible soil. Also, substantial grading can be required to develop level building pads, which results in more areas having deep fill. The oedometer (also known as a consolidometer) is the primary laboratory equipment used to study the settlement behavior of soil. The oedometer test should only be performed on undisturbed soil specimens, or in the case of studies of fill behavior, on specimens compacted to anticipated field and moisture conditions. Figures 6.20 and 6.21 present the results of a collapse test performed on a soil FIGURE 6.21 Laboratory collapse test results for a silty sand. This plot shows the vertical deformation versus time after the soil specimen was inundated with