Ballfield Dimensions Guide

Setting Base Anchors

With Major League and Minor League Baseball recently moving away from 15″ square bases to 18″ square bases for safety purposes, it is likely this change will filter down through other governing bodies of baseball and possibly softball over time. Meanwhile, during this transitional period, there will be instances of ballfields that need to set up their fields with base anchors for both size bases. This step-by-step should help you in setting anchors for 15″ bases or 18″ bases, as well as situations where you may need the ability to accommodate both sizes on the same field. We always recommend making concrete anchors that are in the exact shape of the base for easy and accurate alignment during installation.

BASE ANCHORS MATERIALS LIST:

For each 15″ base anchor:

  • Two 15″ long 2x4s — “shorter 2x4s”
  • Two 18″ long 2x4s — “longer 2x4s”
  • 18″ x 18″ square piece of ½” plywood or OSB board for each form. (1)
  • Concrete Form Release Agent, available most retailers where bagged concrete mix is sold.

For each 18″ base anchor or combo anchor (15″ + 18″ combo):

  • Two 18″ long 2x4s — “shorter 2x4s”
  • Two 21″ long 2x4s — “longer 2x4s”
  • 21″ x 21″ square piece of ½” plywood or OSB board for each form. (1)
  • Concrete Form Release Agent, available most retailers where bagged concrete mix is sold.

STEP-BY-STEP:

[Drawings 1, 2 & 3: Diagrams for a concrete anchor form.]

1. How to create concrete anchors.

A. Build three forms. Each form will require two shorter 2x4s, two longer 2x4s, and piece of ½” plywood or OSB board. Exact lengths are based on the size of the base anchor (see materials list, previous page). Nail, screw and/or glue the pieces together as shown in Drawing 1. When finished, the inside of the box should be the same size as the base: either 15″ x 15″ or 18″ x 18″.

B. Position the anchor on the “X”. Using a chalk line or a pencil, use a straight edge to draw diagonal lines from corner to corner on the inside bottom of the form creating an “X” (see Drawing 2). Spray the bottom and sides of the inside of your forms with a concrete form release agent to prevent the concrete from sticking to the forms once cured. Then center your anchor (1″ or 1-1/2″) on the “X” so that the sides of the anchor are parallel to the sides of the wooden form. Be sure that the flared end of the anchor is at the bottom of the form box. Repeat this step for all three base anchors

If you have a combo field where both the 15″ and 18″ bases will be used, then two of your three concrete base anchors will need a double-anchor sleeve setup embedded in the concrete. For 2nd base, a combo field will simply use a standard anchor block setup with just one centered anchor sleeve as shown in Drawing 2. For 1st and 3rd base you will need to add the second anchor. The second anchor should butt to any of the four corners of the centered anchor as shown in Diagram 3, making sure the opposite corner of the anchor aligns with the scribed diagonal.

C. Fill forms with concrete. Mix an 80lb bag of Redi-Mix concrete as directed on the package. Have someone hold the anchor or anchors in place the whole time you are pouring the concrete. Fill the form to the top with concrete and allow at least one day to cure, preferably longer.

2. Locate the base anchor positions on your field.

(Assuming home plate is in place and a centerline can be established.)

A. Find the center of 2nd base. With the centerline in place, refer to the Field Dimensions Diagrams to find the correct Infield Hypotenuse dimension (letter C on the diagram). Measure with a steel measuring tape from the apex of home plate (following the centerline) to the distance indicated for the Infield Hypotenuse. Place a tarp pin or nail at that spot on the centerline. This is the center of 2nd base. (click diagram to zoom)

[Drawing 4: Installing base anchors.]

B. Measure to 1st base. From the pin at 2nd base measure the distance where 1st base will be positioned (refer to letter A on the Field Dimensions Diagrams). Using a second steel tape, measure the required base distance from the point of home plate to 1st base. Where the two tape measures intersect at the proper measurement, set another tarp pin or nail. This is the back foul corner of 1st base. Note: This measurement is the same, regardless of base size.

C. Measure to 3rd base. Now repeat the process to position 3rd base. From the 2nd base pin measure the proper base distance to 3rd base. Using a second tape, measure from the point of home plate to 3rd base. Where the tape measures intersect is the proper location to place your tarp pin. This is the back foul corner of 3rd base. Note: This measurement is the same, regardless of base size.

D. Make sure the base path is square. Now that you have measured and pinned all of your bases, you must ensure the base path is square. Measure from the apex of home plate to your 2nd base pin and, with a second tape, from the 1st base pin to the 3rd base pin. These measurements must be identical for your base layout to be perfectly square. Adjust as needed until all measurements are correct.

E. Position the anchor accurately. Using the string line as your guide, maneuver the anchor so one edge of the concrete is directly below the string line, the back foul corner of the concrete is where your pin was placed, and the rest of the concrete is on the “fair side” of your string (see Drawing 4). Measure from the point of home plate to the back foul corner of the concrete anchor to ensure correct base placement. You may want to temporarily place a base in the anchor for easier measuring. When you are placing a double-anchor setup for 1st or 3rd base locations of a combo field, the off-center anchor will be positioned toward the outside corner as shown in Drawing 4. This ensures proper alignment of your 15″ bases. After adjusting your base anchor accordingly for correct placement, recheck for levelness and proper depth and adjust if needed.

3. Install 1st and 3rd base anchors.

A. String it up and dig a hole. Starting at the point of home plate, run a string line up the foul edge of the foul line well past the 1st or 3rd base pin. This string line should be slightly to the foul side of your 1st or 3rd base pin. To be installed correctly, the base should cover the foul line as it runs under the base. Next, excavate an area about 2′ square where the base should be located (see Drawing 5). Excavate this area knowing the pins you set indicate the back foul corner of the base. Most metal anchors are about 8″ long and your 2′ x 2′ hole for the anchor should be 8 ½” to 8 ¾” deep. The top of the anchor post should always be ½” to ¾” below the surface so it is never caught when nail dragging. Make sure that the bottom of the hole is level and well compacted.

[Drawing 5: Cutaway of base anchor installation depth.]

B. Place the anchor. Remove one of the concrete anchors from its form by turning it upside down and pounding the form with a rubber mallet to loosen. Make sure that there is no concrete inside the steel anchor post. To maintain proper drainage, clear any excess concrete if necessary. Using a 2×4, create a bridge across the hole and over the anchor post. Ensure that there is a gap of 1/2″ to 3/4″ from the top of the anchor post to the bottom of your 2×4 bridge. If not, remove the anchor, correct the sub-grade, and remeasure the depth.

C. Is it level? Once your depth is set, make sure the anchor is level. Use a torpedo level on the sides of the anchor post. If necessary, adjust the grade under the concrete anchor until it is level.

D. Position the anchor accurately. Using the string line as your guide, maneuver the anchor so one edge of the concrete is on the string line, the back foul corner of the concrete is where your pin was placed, and the rest of the concrete is on the “fair side” of your string (see Drawing 4). Measure from the point of home plate to the back foul corner of the concrete anchor to ensure correct base placement. You may place a base in the anchor to make for easier measuring. After adjusting your concrete anchor accordingly for correct placement, recheck for levelness and proper depth. Adjust if needed.

E. Bury the anchor. When all three parameters are met (distance, depth, levelness), the anchor can be buried. Add soil a few inches at a time. Compact thoroughly before adding the next few inches. Continue until the level of soil in the excavated area matches the grade of the surrounding infield skin. Compact the soil, then moisten and apply topdressing if used.

[Drawing 4]

4. Install 2nd base anchor.

A. Dig a hole and level it out. The 2nd base pin you placed marks the base’s exact center. Therefore, excavating 1′ out in all directions from the base pin will create a 2′ square area. Follow the same process of excavation and leveling as you did in Step 3 with the 1st and 3rd base anchors.

B. Find the exact center of 2nd base. No matter which size base you are using, or if you are on a combo field, you will only need one centered anchor for 2nd base. The centered alignment is the same for all base sizes. Place the concrete anchor in the hole. Stretch your steel measuring tapes from the back foul corners of both 1st and 3rd base toward 2nd base. The exact center of 2nd base is where the two tapes form a right angle at the proper base distance. (See letter A in the Field Dimensions Diagrams.) Center the anchor post at that point (see Drawing 4), making sure the sides of the concrete anchor are parallel to the foul lines.

C. Bury the anchor. When all three parameters are met (distance, depth and levelness), the anchor can be buried, just as you buried the 1st and 3rd base anchors.

5. Test each base, troubleshoot if necessary.

With the anchors now in place, test them by installing the bases to see how they sit on the infield skin surface. The base will sit flush to the skin surface with no gaps. If you see gaps from the base sitting up too high, troubleshoot these common installation problems:

  • The steel anchor post is not level (plumb).
  • The infield skin in not level, and it does not match the surrounding grade causing low areas around the base.
  • How old are your bases? It is possible the bottom edges are curled up.

All of these problems present a risk to players. You should correct any of these conditions immediately to reduce any risk of injury.