Using a transit or laser is the best way to check for level. A water level can also be used. Once a level foundation has been established, you are ready to cut, drill, and set the mudsill in place.
The foundation and/or slab should be ready for you to start framing when you first arrive. Sometimes, however, this is not the case, and time will be needed to “shoot" (measure using a transit or laser) a foundation and slab. Time must also be allotted to fix any problems in the concrete. It will be your responsibility to check and make a suggestion if you think corrective work is necessary. Start by checking and recording your findings. Record your findings in a way that lets you use the information if you decide the concrete needs corrective work. To record your findings, make a footprint sketch similar to the one you used for dimensions and squaring, and write the readings on the footprint. (See “Footprint Sketch Elevations" later in this chapter.)
To take the measurements using a transit, one framer should hold a tape measure at the spots to be measured, while another framer uses the transit to record the height to the transit line from the concrete. To take a measurement using a rotary laser, one framer records the measure at the spots to be measured using a detector that reads the laser beam.
If you are working with a foundation wall or an existing wall, a rotary laser is efficient because once you have the laser set up, you can just mark the red line and measure up or down from it. If the concrete work is done well, typically within a variance of W, then just shooting at strategic locations on the concrete should be
sufficient to check for level. If you quickly find out that the concrete is not level, you will need to shoot the concrete every four to eight feet along the walls. Either way, be sure to record the measurements on the footprint sketch. Mark the locations where the measurements were taken. When you start building walls, you will use the measurements in the footprint and the marks on the concrete to determine stud heights. The marks are only made every 4′-8′, because when you are laying out walls, a level can be used to find the heights between the marks. Another way to find the stud heights between marks is to use a chalk line at the top of the wall to rub studs against and mark the heights.
(See “Chalk Line at Top of Wall" photo.)
Once you have finished a footprint with the elevations marked, you can determine if any corrections need to be made. With the elevations written down, you can show the footprint to the superintendent or owner to let them decide what tolerance they will accept on their building.
If you look at the “Footprint Sketch Elevations" illustration, you will notice that most of the building elevations center around 49W and are within W. The top wall on the sketch, however, appears to be low, with the lowest point at 495/8n. Although 495/8n is more than 49W, it actually represents a low point, because the measurement represents the distance from the transit line down to the concrete.
On the footprint sketch example, you would probably want to use a height of 49W and recommend adjusting the section of the building that is low.
The Xs on the footprint represent the position of your tape measure when you shoot the height with the transit. Mark the X on the concrete so that when you start building walls, you will have a reference point if your heights need adjustment. Also keep your footprint sketch for this purpose.
Finding stud heights when the slab or foundation is not level is difficult. It is even more so when the foundation steps up or down to different heights. Using a transit requires you to measure everything from the height that is established when you set the transit. It could be measuring up or down from the transit reading line. It is hard to keep all the numbers in your head when you start adding and subtracting for the different concrete levels and the levels of the foundation.
The best way to find the individual stud heights is to write everything you need for each individual stud down on a piece of paper and figure the stud height from those figures.
The illustration “Stud Heights for Different Foundations" illustrates how to do this and includes a “Job Site Worksheet." Whenever you move the transit, it changes the measurements, so you would have to start over if you did not have all the measurements you need for a particular area. It is easier to finish one area completely before moving the transit.