One method is as follows: 1 Mark the two end points of the wall in accordance with instructions. The marks could be in chalk or a thin spread of mortar marked with a line made with the point of the trowel to indicate the required dimension. (Note: You may decide to set out the first course dry to ensure uniform joint sizes will be achieved, as already discussed.) 2 Lay a brick on a mortar bed at both ends of the wall to correspond with the marks. Try to line them up with each other by eye for now. The beds should be 10mm, but may need to be adjusted as well see in a moment. 3 Since the wall is likely to be longer than the length of a spirit level, we will need to use a straight edge to transfer a level reference from one end of the wall to the other. Our spirit level is placed on top of the straight edge so that we can now level over a greater distance. 4 We will now probably need to make adjustments to one of the bedded bricks. Checking the spirit level will tell us whether we need to raise or lower one brick to make it level with the other. We could also place our straight edge against the face of the bricks to line them up more accurately with each other.

With member size of particular importance of fire endurance of wood, building codes classify buildings with wood framing as heavy-timber construction, ordinary construction, or wood-frame construction. Heavy-timber construction is the type in which fire resistance is attained by placing requirements on the minimum size, thickness, or composition of all loadcarrying wood members; by avoidance of concealed spaces under floors and roofs; by use of approved connections, construction details, and adhesives; and by providing the required degree of fire resistance in exterior and interior walls. (For design procedures and typical connector details, see Design for Code Acceptance #2, Design of Fire-Resistive Exposed Wood Members, American Forest & Paper Association, Washington, D.C.) Ordinary construction has exterior masonry walls and wood-framing members of sizes smaller than heavy-timber sizes. Wood-frame construction has wood-framed walls and structural framing of sizes smaller than heavy-timber sizes. Depending on the occupancy of a building or hazard of operations within it, a building of frame or ordinary construction may have its members covered with fireresistive coverings. The fire endurance rating of protected wood-frame assemblies is measured in a standard fire endurance test, ASTM E119. Fire endurance ratings for various assembly designs can be found in listings that are published by recognized fire testing laboratories. These listings are updated on a regular basis. Alternatively, for many assemblies, a conservative estimate of the fire endurance rating can be obtained through a simplified calculation method (Design for Code Acceptance #4, Component Additive Method (CAM) for Calculating and Demonstrating Assembly Fire Endurance, American Forest & Paper Association.) This method estimates the overall fire endurance rating as the sum of fire endurance times assigned to individual components of an assembly. The interior finish on exposed surfaces of rooms, corridors, and stairways is important from the standpoint of its tendency to ignite and spread flame from one location to another. The fact that wood is combustible does not mean that it will spread flame at a hazardous rate. Code requirements to limit the flame-spread propensity of interior finishes are based on the flame-spread index (FSI) measured in the ASTM E84 tunnel test. Most wood products of sufficient thickness (1/4 in or greater) have an FSI between 76 and 200 (Class III or C). Some wood products have an FSI between 26 and 75 (Class II or B). Fire-retardant treatment can improve performance to an FSI of 25 or less (Class I or A). For an extensive list of flame spread indices of wood products, see Design for Code Acceptance #1, Flame Spread Performance of Wood Products, American Forest & Paper Association. In general, codes require Class I or A materials for enclosed vertical exits. Class II or B materials in exit access corridors, and Class III or C materials in other areas and rooms. Thus, wood products are accepted by the codes for a wide range of interior finish uses. Most codes exclude the exposed wood surfaces of heavy-timber structural members from flame-spread requirements, if the exposed area is sufficiently

For Class C fires, water can be applied to live electrical equipment if it is done in the form of a nonconducting foglike spray. This is usually the most economical way to protect outdoor oil-filled transformers and oil circuit breakers. Fire protection should be based on complete coverage of the building by the sprinkler system. Partial coverage is rarely advisable, because extinguishing capacity is based on detecting and extinguishing fires in their incipiency, and the system must be available at all times in all places. Systems are not designed to cope with fires that have gained headway after starting in unsprinklered areas. See also Arts. 14.27 to 14.29. Standpipes. Hoses supplied with water from standpipes are the usual means of manual application of water to interior building fires. Standpipes are usually designed for this use by the fire department, but they can be used by building fire fighters also. Standpipes are necessary in buildings higher than those that ground-based fire department equipment can handle effectively. The Standard Building Code requires standpipes in buildings higher than 50 ft. The Uniform Building Code requirement starts at four stories or occupancies over 5000 ft2 in area and depends on whether automatic sprinklers are installed. See also Art. 14.30. Chemical Extinguishment. Fires involving some materials may not be readily extinguished with water alone. When such materials may be present in a building, provision should be made for application of appropriate chemicals. Foamed chemicals, mostly masses of air- or gas-filled bubbles, formed by chemical or mechanical means, may be used to control fires in flammable liquids. Foam is most useful in controlling fires in flammable liquids with low flash points and low specific gravity, such as gasoline. The mass of bubbles forms a cohesive blanket that extinguishes fire by excluding air and cooling the surface. Foam clings to horizontal surfaces and can also be used on vertical surfaces of process vessels to insulate and cool. It is useful on fuel-spill fires, to extinguish and confine the vapors. For fire involving water-soluble liquids, such as alcohol, a special foam concentrate must be used. Foam is not suitable for use on fires involving compressed gases, such as propane, nor is it practical on live electrical equipment. Because of the water content, foam cannot be used on fires involving burning metals, such as sodium, which reacts with water. It is not effective on oxygen-containing materials. Three distinct types of foam are suitable for fire control: chemical foam, air foam (mechanical foam), and high-expansion foam. Chemical foam was the first foam developed for fire fighting. It is formed by the reaction of water with two chemical powders, usually sodium bicarbonate and aluminum sulfate. The reaction forms carbon dioxide, which is the content of the bubbles. This foam is the most viscous and tenacious of the foams. It forms a relatively tough blanket, resistant to mechanical or heat disruption. The volume of expansion may be as much as 10 times that of the water used in the solution. Chemical foam is sensitive to the temperature at which it is formed, and the chemicals tend to deteriorate during long storage periods. It is not capable of being transported through long pipe lines. For these reasons, it is not used as much as other foams. National Fire Protection Association standard NFPA 11 covers chemical