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Every building has to start somewhere. After clearing and leveling the building site, Batter boards are the first step of most construction projects with rectangular foundations. Batter boards and string lines are a great technique to use in building a foundation that is square and level. The idea is to have strings intersecting at each corner of the foundation. This is accomplished by setting batter boards a few feet outside the foundation corners and attaching strings to the top of them that will run along the outer edge of the foundation. A batter board is a simple structure with stakes driven vertically into the ground with a horizontal board across them. Here is how to do this yourself.
Building a batter board:
Setting batter boards is a multi-step process. The basic steps are:
- Construct the batter boards
- Level the batter boards
- Add the string lines
- Adjust everything
How to complete these steps is described below.
What you will need:
You can use steel stakes that are manufactured for concrete forms, or boards cut to a point on one end. Scraps of 2x4s or other lumber will be fine for the boards. Screws are preferred to nails for attaching the boards to the stakes and for the strings as they are easier to remove for adjustments.
How to assemble a batter board:
Drive a pair of stakes into the ground outside of where each corner of the foundation will be. Attach a horizontal board to the stakes after they are driven into the ground. Allow enough space to adjust string placement. You can either build two separate batter boards on each corner like in the photos or a three cornered/two sided one like in the video. Two separate ones will allow you to set them farther outside the foundation in order to provide more working space.
Setting batter board height:
The batter boards must all be at the same height in order for the string lines to be level. Typically you want this height to be where the top of the foundation will be. The height can be adjusted by pounding the stakes further into the ground. It is helpful to leave them a little high to start with because it is easier to make adjustments by pounding them farther in than to pull them out. To check the height you can use one of the following tools: a transit and builder’s level, a water level, or a laser transit. After getting all of the heights correct, you may want to add a second set of stakes angling into the ground to make everything more sturdy.
Adding the strings:
Once the height of the batter boards are set, decide which wall will be the reference wall. Whichever wall you choose will not be adjusted after it’s set–so choose wisely. Is there one wall tight to setback requirements? Are there buried utilities stubbed in that need to be a certain distance from the outside edge of the foundation?
Attach the string for the reference wall first, placing it exactly where you want the wall to be. To do this put a screw in the top of each batter board and tie the string to it. Next do the same for the wall opposite the reference wall measuring the distance at both ends of the string. You can use weights to temporarily hold the stings in place while you measure–this is especially helpful when working with less than three people. Next set a string perpendicular to the reference wall using the 3-4-5 method to make the corner square. Set the opposite string (the final one if the building is a rectangle) by measuring the distance from the two string intersection you just created.
Adjusting the batter boards and strings:
This is a fussy process so you will need to check and adjust board heights, distances between string intersections and squareness of the string lines. These adjustments may take a few iterations to get them accurate enough (within about 1/16th of an inch). Start by double checking the height of the batter boards since they may have moved as a result of pulling the strings. Then take measurements again from where the strings intersect, adjusting as necessary. (Remember not to move the string on the reference wall.) Finally check if the strings are square by measuring both diagonals (the distance between opposite corners) which should be the same as one another. Adjust again as needed.
When all of the measurements match your plans you have a good reference to use in building a square, level foundation.