Download - Engineering Surveyor

Buildings and structures: curved wallsCircular wall – centre accessibleIf the centre is accessible and the radius not greater than, say, 30 m, it is convenient to set out the first course of abrick wall by taping from the centre (similarly for the kicker of a concrete wall). The bricklayer works by plumbingvertically with a spirit level and checking segments of the curve with a timber shaped to the radius.If the centre is available, and the radius is less than say, 5 m, a scaffold pole can be set up as the centre for atrammel board as shown in the diagram. The inner and/or outer radius is marked on the trammel, which is raisedcourse-by-course with a scaffold clip to control the level of the wall.Circular wall – centre not accessibleWhere the centre is not accessible, the curves must be set out using deflection angles and chord lengths. Chordintervals should be about 3 m.For example, the method for a concrete wall could be: set out centre-line establish offset pegs erect profiles, excavate and place foundation set out kicker accurately from offset pegs – place kicker set up forms and plumb down to offset pegs or secondary offset points.Serpentine wallsSerpentine or S-shaped walls are difficult to set out accurately by using deflection angles and chord lengths. Analternative is to use a baseline and offsets, so long as the offsets lie within a convenient taping distance. Offset pegscan be established on the baseline at suitable intervals. The offset distances can be calculated or taken off thedrawings, provided the geometry of the wall is known.CIRIA C70981