My son is building a house on 8 x 8 wood pilings. The pilings have been installed. The house is to be 40' long by 28' wide. How do you establish a level line to begin the installation of the flooring beams ?
You can use a builders level (commonly called a transit, even though they are slightly different instruments), a laser level, or a water level. The water level is the most basic and inexpensive to acquire, needing only a long length of clear plastic tubing with a few drops of food coloring in the water. This is your best bet if you do not have access to borrow or rent one of the other instruments. Do not be tempted to buy one of the cheap laser instruments you often see at big box centers, as their degree of accuracy is way too poor for establishing a level plane for a foundation.
If you are in an area requiring regulatory inspections, you will most likely need to hire a surveyer to establish a benchmark for elevation reference before you build, and to verify the height of the building before the regulating authority will close out the permit. If so, ask them how much they would charge to give you a reference mark on each piling, then use a framing square to draw this mark out to the corner of each piling, and take a hacksaw or any fine toothed blade and make a small saw kerf at one corner of each piling. You now have a permanent level reference for all future work.