Of course, limits must be applied to the height of any brick wall during the construction process since the mortar must be given time to set to its working strength. Masonry is relatively fragile until the mortar is completely set and the wall is integrated into a building or complete structure. A wall built from heavy components, like bricks laid in a soft material like mortar, can be vulnerable to strong winds blowing into the face. For this reason care must be exercised by the bricklayer not to build too high in one working day. The optimum height to which a wall can be built in one work period will be determined by the type of brick, the consistency of the mortar, and the weather conditions, both at the time of building and expected in the near future. As a rule of thumb, be cautious about building unsupported brickwork higher than 12 courses at one time (especially for half-brick walling). Whilst its possible to build higher than this, the specification for a particular job may actually direct the bricklayer to build to fewer than 12 courses at one time, sometimes as few as six courses. If in doubt, ask your supervisor or line manager.

Corner blocks are made of plastic or wood and use the tension of the string line stretched from end to end to keep them in position. They are easy to make from timber available on site. They make it quick and easy to adjust the string line up the wall for each course of brickwork to be laid. Look online at a building tool supplier website (start with Buck & Hickman.) Check out the types of corner blocks that they sell. Look at the corner blocks in Our House too, as an additional guide to how the blocks should appear. Corner block Having considered how we set out and build a straight wall, lets look at how we set out a wall that has corners specified for the design. In brickwork, a corner has an unusual name: a quoin. A corner or quoin, is usually set out as a right-angle; in other words it is set out at 90. (There are quoins set out to other angles that you will learn about as you progress to higher levels.) In Chapter 3 you will find more details about setting out squares and rectangles using a number of methods.

To find reaction R1, we take moments about R2 and equate the sum of the moments to zero (clockwise rotation is considered positive, counterclockwise, negative): R  14,000 lb 1 In this calculation, the moment of the uniform load was found by taking the moment of its resultant, which acts at the center of the beam. To find R2, we can either take moments about R1 or use the equation V  0. It is generally preferable to apply the moment equation and use the other equation as a check. R  13,000 lb 2 As a check, we note that the sum of the reactions must equal the total applied load: 5.5.3 Internal Forces Since a beam is in equilibrium under the forces applied to it, it is evident that at every section internal forces are acting to prevent motion. For example, suppose we cut the beam in Fig. 5.17 vertically just to the right of its center. If we total the external forces, including the reaction, to the left of this cut (see Fig. 5.18a), we find there is an unbalanced downward load of 4000 lb. Evidently, at the cut section, an upward-acting internal force of 4000 lb must be present to maintain equilibrium. Again, if we take moments of the external forces about the section, we find an unbalanced moment of 54,000 ft-lb. So there must be an internal moment of 54,000 ft-lb acting to maintain equilibrium. This internal, or resisting, moment is produced by a couple consisting of a force C acting on the top part of the beam and an equal but opposite force T acting on FIGURE 5.18 Portions of a beam are held in equilibrium by internal