concrete sitework layout
Layout for concrete sitework (curbs, pavement, sidewalks, etc) will consist of a professional surveyor pounding lath stakes every so often along the edge of the pavement, sidewalk, or curb. Typically offset stakes are provided to allow for forms to be constructed without affecting the layout stakes, so they can remain in place and be referenced when needed. A common offset distance is usually 4′. This allows plenty of room for the excavation, fine grading, and forming crews to complete their work. The stakes may also have elevations and/or hub/tack on them allowing the top of pavement elevation to be checked before concrete is placed. The top of the wood or metal form is checked against the elevation listed on the stake which often comes from a pre-engineered system of elevations from a CAD file or from the grading plan.
Also, vertical layout is critical, particularly in terms of concrete pavement and slabs, as they are often designed to sheet drain away from the pavement or into catch basins. Typically a grading crew will prepare the area and compact it prior to the concrete forming crew. If the concrete is sloped for sheet drainage and is not to be placed at one consistent elevation, grades are checked at various points within the slab area using grades shown on a plan in reference to a known benchmark. From there the field calculation is made. As long as the stone base grade is laid out accurately, the concrete depth should be consistent and the elevation of top of concrete should be accurate (the concrete crew can check it every so often by dipping a pole, stick, or tape into the wet concrete and observe the distance between the stone grade and top of concrete, and adjust accordingly). If the grades are incorrect, not only will you have inconsistent concrete depths below, but your pavement may not slope to drain the way it was designed to.