setting grade
Double-Check Grade Sheets
A common practice is to review the project plans and write down the needed elevations or calculate the needed elevations onto a "Grade Sheet." The grade sheet may contain elevations to be established for dirt work, elevations for concrete pours, or any other needed elevation. Sometimes the sheets are called cut sheets or fill sheets if cut or fill amounts are to be written on the stakes. Regardless what they are called, their impor-tance is the same. If any mistake is made in obtaining an elevation from the plans or if elevations are calculated incorrectly, the elevations established in the field will be wrong. Any time grade sheets are used, they should be prepared by two persons inde-pendently and compared. Any differences should be rechecked to see who is correct. For super-critical elevations such as the top of a bridge pier, triple-checking by three persons using different methods should be used. When the concrete is hard, it is too late to use an eraser to check your elevations. At that point a jackhammer is used to erase the mistake—at great cost to someone.
Procedure For Setting Grade
The types of elevations needed on the jobsite vary from grade on excavation stakes to grade on formwork and many other applications. The process is essentially the same whenever grade is being established. That is, the level is set up, the HI determined, an intermediate foresight taken to determine the elevation of the ground, and a cut or fill written on the stake to direct the crafts to build to that elevation. A more detailed explanation of setting stakes for the footings of a small building is described below.
Use an eraser, not a
jackhammer to find mistakes.
To construct footings requires that soil or rock be removed to be able to place the footing at the proper location horizontally and vertically. The horizontal location of the footings will be determined by layout techniques described in Chapter 19, Layout Techniques, and marked with stakes that are offset from the center of the footing.
Step 1
Once the location of the footing for the building is established, elevation is need-ed so that the excavation contractor can excavate to the bottom of the footing. On the plans, this elevation may not be directly given. More likely, the top of footing elevation will be given or maybe even just the finish floor elevation will be known. Regardless, the elevation must be determined and a grade sheet developed.
Step 2
ch 19