How to Build a Baseball Field – Natural Grass Pitch (With Sketch Drawings)
Layout of Baseball Field
How To Build a Natural Grass Baseball Field
Setting Out the Overall Baseball Field
Baseball Field Substructure
Building the Pitching Mound
Building 1st, 2nd and 3rd Base
Building the Batter’s Boxes, Catcher’s Box and Home Plate in the Home Circle
Baseball is a popular sport in the USA, which you might mistake for English cricket (commonly played in British Commonwealth countries) because of their many similarities. Both games originated in England although cricket is the older of the two. The games were imported to the USA by British settlers in the 1800s, and as time went on baseball became more popular than cricket after the 1865 American civil war. In the American MLB (Major League Baseball), each team has 9 or 10 players depending on the rules. In cricket, each side has 11 players.
A baseball field may look like an ordinary athletic sports pitch, but it involves complex planning, design and construction. This is due to the fact that the pitch is not flat throughout, and its layout is more challenging than a football field. When building an NHSF or MLB regulated field for collegiate and professional tournaments, a high level of accuracy is required when grading the infield slopes to ensure that the elevations of the pitching mound, home plate and bases are maintained according to the rules. The challenge comes when you are trying to integrate a suitable drainage system for the field. Surface rainwater has to be drained off and away from the field, so how do you grade and build an efficient drainage system that doesn’t interfere with the Sports Body regulation rules for setting out the field and dimensions?
Slope and drainage are some of the things that you have to consider when building a baseball field. In the planning stage of your project, there are many things that you have to consider. This includes deciding the overall size of your pitch, the stadium and its features besides the infield. Are you going to have a field with spectator stands, backstop fencing, car parking, outfield fencing, access points (gates) for spectators and players, extensive lighting, ticket booths, ablution facilities, separate dugouts (boxes or sitting areas) for the coach and players? Some of these things may be optional if you are building a residential or recreational baseball field that is not used for professional or regulated tournaments. An MLB professional league and collegiate baseball field is much bigger than an NFHS senior and junior high school field. The former is 110,000 square foot, and the later is 90,000 sf and 60,000 sf respectively.
Baseball involves the batter in the home circle swinging at the ball with a bat, outfielders (left, centre and right fielders) catching fly balls in the air or on the ground and throwing them back to the infield. Infielders (1st,2nd and 3rd baseman, and shortstop) are responsible for catching throws from outfielders, fielding balls from the batter, making and catching throws to and from other basemen. The pitcher stands on the pitching mound or circle and his role is to throw (pitch) the ball towards the home plate. Pitching is a highly specialized skill that requires specific (arm, hand and wrist) positions and movement to produce the required pitch (launch angle, trajectory and speed).
In baseball, players can readily switch or assume different roles and positions in the game with the exception of the more specialized roles for catcher and pitcher which are often hard for other players to master or play. Non-specialized roles such as batting and fielding can be made in turns by players, but for specific fielders such as the second and third baseman, shortstop, centre and right outfielders, there are certain skills, abilities and physical attributes which are required for better performance.
The orientation of your baseball field is important. The orientation of the field in relation to the sun must be such that the players, especially the batter, pitcher and catcher, are not affected by sun glare during play. The MLB rule 1.04 states that a baseball field must have its centreline (imaginary line projecting from the home plate to the second base through the pitching mound plate) aligned in the East to North East direction starting from the home plate. This field orientation ensures that the sun is not getting in the player’s eyes during an afternoon or dusk game. If you are going to have games solely in the morning, you will need to change the orientation for that purpose to counter and minimize the effects of sun glare during that time of the day. So the question to ask before you build a baseball field is will it be used for afternoon or morning games?
In the preliminary stage of your baseball field construction project, you will start by making site investigations. The geotechnical engineer will investigate ground conditions, the soil profile and carry out several soil tests. He or she will determine the location of existing utility services such as site drainage systems, water supply pipes, gas pipes, electricity and telecommunication cables. This will involve calling the 811 Dig Safe number to get all utility line operators to identify and mark the positions of all underground services on the site.
The site engineer has to determine other preliminaries which may affect the site such as access to site, adjacent buildings and property, terrain, roads, climate, environmental impact and local zoning laws. All these details will be available in the engineer’s report as well as the feasibility study carried out by all technical experts and stakeholders involved in the project. The feasibility study will determine whether the project can go on or not, outlining all obstacles, hazards, challenges as well as solutions to these problems. As long as there is no approval from the local authorities or building department in your city, county or state, the project cannot go on. You need to secure a building permit first.
Layout of Baseball Field
Before you ask “How do you build a baseball field?”, you have to understand the layout of a baseball field and its dimensions. Basically, a baseball field has two main parts, the infield and outfield. The infield is enclosed by the outfield which defines the overall shape of the baseball field. The overall shape of a baseball field is like a diamond. While the outfield is shaped like a diamond, the infield is also shaped like a diamond. However, within the infield, there is a square base with green turf. The square is tilted on its bottom corner so that the corner has the same corresponding angle (or direction) as the diamond corner of the infield. In a professional or collegiate league baseball field, the infield base is a square 90×90 foot long. It is bounded by foul lines on the left and right, and baselines in the interior, base 1-2 on the right and base 2-3 on the left.
We said the outfield is the overall area enclosing the infield. Both the infield and outfield are measured from the home plate (the bottom tip of the diamond) at the intersection of the foul lines. The outfield is bounded by grass lines and warning track which form the perimeter of the field.
The infield has grass lines which are 3 inches outside the foul lines. As a rule, the distance or diameter of the outfield from the home plate ranges from 290 to 400 feet depending on the type or size of the field. According to MLB building codes, in a 90×90 feet baseball field, the minimum distance of the foul line from the home plate for an outfield is 325 feet.
Now that we have laid out the plan of a baseball field, the next step is defining the points and features on the field.
The infield has grassed and skinned areas. The square base within the infield is a grassed area with 4 corners at 90 feet apart. The bottom corner is known as the Home Plate and it is located in the centre of the home circle which has a radius of 13 feet. The batter’s and catcher’s boxes are located inside the home circle. On the right side of the home plate, you have a box for a left-handed batter, and on the left side of the home plate, you have a box for a right-handed batter. The batter’s box is 4 feet wide x 6 feet long, divided longitudinally into two equal parts which are 4 feet wide x 3 feet long. The batter’s box is 6 inches (152mm) from the side of the home plate on both sides (left and right). Behind the batter’s boxes is the catcher’s box, which is 43 inches wide and 8 feet from the tip of the home plate. The home plate is a 5-sided shape with a rectangular base and triangular apex. The size of the rectangular base is 17 inches x 8.5 inches, and the apex is a triangle with a base length of 17 inches and height of 8.5 inches.
The other three corners of the square are known as Bases. The corner on the right side is known as the 1st Base. The left corner is known as the 3rd Base, and the top corner is known as the 2nd Base. So what is installed at the corner bases? Square rubber plugs 15×15 inches wide (381x381mm) and less than or equal to 3 inches thick (76mm) are installed at the corners. First, you will have to dig holes and install concrete bases with a tubular steel anchor embedded in the centre of the concrete base.
In the centre of the infield square, there is a circle known as the pitching mound or circle. The pitching mound is an elevated area with a radius of 9 feet, rising at a height of 10 inches (254mm) above the home plate.
Just in front of the pitching mound centre, a rectangular rubber 24×6 inches wide, known as the pitcher’s plate is installed on the mound. The pitcher’s plate is flush and level with the top of the pitching mound, so its height from the home plate level to the top surface of the mound will also be 10 inches (254mm). The distance of the pitcher’s plate from the corner of the home plate to the front face of the rubber plate is 60 feet 6 inches (60.5 feet).
The length of the infield centreline (the diagonal line dividing the square from the corner of the home plate to the corner of the 2nd base) is 127 feet 3.38 inches (127.28 feet).
A baseball pitch has portions with green grass or turf as well as portions with no turf which are known as skinned areas. Skinned areas have a clay surface, that’s why these areas look red in contrast to the green turf.
Skinned Areas of a Baseball Field
The following are the skinned areas on a baseball pitch:
Infield Outer Area
The diamond shaped infield has a clay area surrounding the inner square formed by the bases. The pitching mound, home circle as well as the foul line path on the left and right side of the square base are also clay areas. Note that inside the pitching circle and home circle, the footing lane or boxes inside the circle are fortified with bagged clay or clay bricks to resist wearing out, as these are high traffic areas.
A warning track is a perimeter strip surrounding the entire baseball outfield. Just like the infield outer area, it is a skinned area with no turf, but instead of clay, the warning track is paved with material that is different in both colour and texture to the outfield and infield. Rubber surfacing, asphalt and coarse aggregate of particle size less than or equal to 0.375 inches is often used as a surfacing material on a warning track. The surfacing material is 4 inches deep (100mm), laid over a compacted sub-base course.
A warning track is 15 feet wide (5m) in MLB regulated fields, and 20 feet wide (6m) in Olympic Game fields. What is the purpose of a warning track on baseball fields? Earlier one, we said a warning track should have a different colour to that of the infield and outfield. This helps the players (outfielders) to avoid going out of range when running across the field in an attempt to catch fly balls. As they are running across the field, the players will easily notice that they are approaching the grass line and encroaching into the warning track. A player should decelerate on approaching the warning track to avoid hitting the boundary wall or fence around the outfield, as this may cause injury to oneself. Another use of a warning track is providing a path or road for maintenance vehicles to move or park on during a maintenance schedule.
Green / Turf Areas of a Baseball Field
Infield Inner Area
The infield inner area is a square base with green grass or turf. The only part that is not covered with grass is the pitching circle.
The diamond-shaped outfield is covered with green grass, with the exception of the warning track surrounding the area, and of course the infield.
How To Build a Natural Grass Baseball Field
Building a baseball field starts with finding a suitable location, and whether or not you can build a sports field in that location depends on local zoning laws, so you will need to have your plans approved by the building department before you get a building permit. Once you have found a suitable location and made the required preliminary site investigations, you should proceed to make drawings for the sports field. After producing the construction drawings, takeoff measurements from the plans and make bills of quantities that should be priced with current market rates to produce a building cost estimate. This cost estimate will help you in budgeting for the project, as well as controlling costs during the contract administration stage.
Before any setting out or construction begins, you must clear the site of all rubbish, vegetation, obstacles, trees, bushes, hedges, shrubs, grass, stones and boulders. Cart away the rubbish to a nearby dump site in your town or city.
Setting Out the Overall Baseball Field
After clearing the site, you will begin by setting out levels on site with profiles and stringlines. At this stage, we are not concerned about the dimensions of the actual diamond-shaped outfield and infield. We just want to set out the overall building site or field. The overall site may be circular, square or rectangular in shape, and it will extend beyond the outfield. Just make sure the baseball outfield can fit within the site with room for the warning track and fence in either orientation of a 360-degree rotation, from North to East, South to West and West to North.
To set out a square or rectangle on a site, corner profiles (batterboards) or wooden pegs can be used. You will need four corner profiles to do this. Drive a profile board into the ground on the first corner (point A), and then another profile on the second corner (point B). Tie a nylon string between points A and B, making sure its taut. Ensure that the profiles are plumb, and the stringline is running level on the top face of the batterboard at a perpendicular angle to the corner profile or peg. If the ground is sloping or uneven, you will need higher profiles (or pegs) on the lower end of the ground and shorter profiles (or pegs) on the higher end of the ground.
Drive into the ground corner profiles on the third and fourth corner, and complete stringlines on all four sides of the square. Make corner to corner diagonal stringlines inside the rectangle, and if the diagonals are of equal length, the set-out is a perfect rectangle.
Grade and Level the Site
At this point, the site is still a natural terrain. It may be an uneven or sloping terrain. If this is the case, then you should grade and level the site to a flat surface. Even if the natural terrain is fairly level, you still have to strip the topsoil to a subgrade level that provides a uniform, level and evenly distributed base to start your substructure construction.
Excavate the natural terrain to a reduced level of 439mm deep from the site datum or benchmark using a laser grader which provides a high level of accuracy. The site datum is usually the required level (or finished level) at which the surface of the sports field should be. When excavating to the required depth from the datum level, there will be cut-and-fill areas where you must excavate and fill with excavated material to achieve level ground and formations. The setting-out pegs, profiles and stringlines will guide you in the course of excavation.
After excavating the site to strip level, you must compact the ground, breaking up lumps of soil, spreading material evenly over the site and filling holes and depressions with excavated material. Compact the soil in 150mm layers with a vibratory roller to 95% MoD AASHTO Density, adding water to moisturize the soil if it’s dry.
Setting Out the Baseball Outfield and Infield
After excavating, grading, levelling and compacting the overall site to a flat stripped level as described previously, your next step is setting out levels for the outfield and infield. As you can see, level prepared ground makes it easier to set out the challenging outlines of a baseball infield and outfield.
Setting Out the Field Orientation / Centreline
Before you set out and paint lines on the field, you have to decide the orientation of your baseball pitch as discussed previously. If your pitch is going to be used for afternoon and sunset games, then the centreline of your pitch must be aligned in the East to North East direction starting from the home plate.
Find a baseline on the field which is nearest to your proposed home plate. It may be a fence, inspection chamber, road or building. If there is no existing baseline or benchmark, you can estimate the position of the centreline by rotating a stringline or measuring tape drawn about the centre of the field in the East-North East direction. Drive a peg in the centre of the field (C), then attach a string or measuring tape with a looped end. Roll out the string / tape to the edge of the pitch (field radius) then rotate the string about the centre (C) while its taut, making sure that its horizontally aligned or parallel to the ground. Using a compass, find the East-North East direction while you are holding the string, then pin the end of the string on point (E) on the ground using a steel pin or peg. The stringline C-E marks and defines the centreline of the baseball pitch. You may as well mark this line on the ground with lime paint if needed. Now that the centreline is known, you should project and extend this line to the other end of the pitch, to complete the diameter of the field.
Setting Out and Marking the Home Plate, 2nd Base
The centreline of the pitch has been determined and marked on the ground. Your next step is marking the position of the home plate (H) on the ground from the end of the centreline (from the East) at an appropriate radius and distance from the fence, boundary line or other benchmark.
Note that the initially marked centre of the field was used to determine the centreline of the whole field in the East to North-East direction. However, when you are setting out the centre of the pitching circle in the infield square, this centre can be shifted up or down the centreline as needed to a suitable position which allows for overall spacing design and requirements on the pitch.
For this project, we are going to shift the centre of the pitching circle down the centreline a bit, to provide space for the outfield on the upper side.
Let’s say the home plate is located on point (H) on the down-end of the centreline. Our infield square is 90×90 feet wide or (27.4 x 27.4m). The infield square has four corners, the 1st base, 2nd base, 3rd base and the home plate. The 2nd base (B2) and home plate (H) are located on the centreline, so the diagonal line B2-H is 127 feet 3 inches (38.80m) 127.08 feet. The diagonal was calculated using the Pythagoras theorem.
Drive a steel pin or timber peg into the ground on point (H). From the home plate (H), measure a distance of 127.08 feet (38.80m) along the centreline, and drive another peg into the ground on point B2.
Setting Out and Marking the 1st and 3rd Base
Our infield square has three known points or markings at the moment. These are the home plate (H), the 2nd base (B2) and the diagonal line between points H and B2. We have to mark the position of the 1st and 3rd base. We will start by marking the 1st base. There are two methods for setting out and marking the positions of these bases.
The first method involves using two measuring tapes. A steel pin or wooden stake is driven into the ground at point (H) where the home plate is located. Another pin or stake is hammered into the ground at point (B2). Get a measuring tape with a loop end and hook it on stake (B2). Hook another tape on stake (H). Now, since your square has equal sides of 90 feet each, the sides B1-B2 and B1-H must be equal. Extend the first tape to an approximate position where you think corner (B1) will be. Do the same for the other tape. The tapes should be kept straight and level with the ground and not inclined or bent. Hold the 90 feet (27.4m) mark on each tape and pin the position where these two tapes intersect. The tapes should intersect at the 90 feet mark. Repeat the same procedure for setting out the position of the 3rd base (B3) with reference to the home plate and second base. The sides B3-H and B3-B2 must be equal.
Alternatively, you can set out the positions of the 1st and 3rd base by first drawing a perpendicular line to the baseline (H-B2) that passes through the centre of (H-B2). We already know the distance (H-B2) is (38.80m) 127.08 feet, so the centre of this line is 19.40m (63.54 feet) from both ends. Drive a steel pin into the ground on point (H) and (B2). Get a nylon string with a looped end and hook it on pin (H), then scribe an arc on the ground. Hook another string on pin (B2) and scribe an arc on the ground. Mark the point where the arcs intersect with a steel pin. The string must be extremely longer than the half-length of the baseline (H-B2) to allow for intersection. Drive in a steel pin on the centre of the baseline (H-B2), which we are going to call (C), then make a stringline from the centre (C) to the point of intersection of the arcs (I). You may as well draw this line on the ground using line marker paint. The line C-I is perpendicular to the baseline. Extend the line to the extreme ends of both sides of the baseline.
To locate 1st base (B1) on the perpendicular line, drive in a steel pin on point (H) or point (B2), then hook the looped end of a measuring tape on one of these points. Extend the tape to the perpendicular line and mark the point where the perpendicular line intersects with the 90 feet mark on the tape. Drive in a steel pin on this point. Repeat the same procedure to locate the 3rd base (B3), using either (H) or (B2) as the reference.
A faster shortcut for this method is calculating the height (H) of a right-angled triangle (B1-C-B2) with a known base length (C-B2) of 19.40m (63.54 feet) and hypotenuse (B2-B1) with a length of (27.40m) 90 feet. Using Pythagoras theorem, the height (H) is 63.73 feet, so the line C-I which is perpendicular to the baseline is 63.73 feet. Using a tape measure, measure a distance of 63.73 feet from the centre of the baseline along the perpendicular line (to the left), and mark the point (B1) on the ground with a steel pin. Do the same on the other side of the baseline. Measure a distance of 63.73 feet from the centre of the baseline along the perpendicular line (to the right) and mark the point (B3) on the ground with a steel pin. That’s all.
Setting Out and Marking the Pitching Circle
The pitching circle is located roughly in the centre of the infield square, but not exactly in the centre as such. The centre of the pitching circle is located on the baseline H-B2 (centreline) near the centre of the baseline, but a little further down the line. The front face of the pitching plate (rubber) is located 18 inches in front of the pitching circle centre on the horizontal plane. The dimension of interest is the distance from the front face of the pitching rubber to the tip of the home plate. This distance is 60.5 feet (18.44m). Note that the pitching circle is gradually sloping on all sides from the top plate, which is at a height of 10 inches from ground level. When setting out the pitching circle, we are not interested in the sloping plane, so the location of the pitching plate as well as the centre of the circle is based on the horizontal plane (ground level).
From the above information, we can see that the centre of the pitching circle is [60.5 – 1.5] = 59 feet away from the home plate (H). Mark the position on the ground with a steel pin. Take a string or measuring tape with a loop end and hook it over the steel pin. Extend the string or tape so that it’s straight, taut and level with the horizontal plane (ground). Hold the 9 foot mark on the tape or string, and scribe a circle about the steel pin. You have just completed an 18 foot diameter circle known as the pitching circle. Additionally, you can scribe the circle on the ground using aerosol athletic field paint.
Setting Out and Marking the Home Circle
The home circle is the circle adjacent to the backstop, containing the home plate, catcher’s and batters boxes. The home circle has a diameter of 26 foot, and the tip of the home plate is located in the centre of the circle, at a radius of 13 foot. To mark the position of the home circle, drive a steel pin into the ground where the home plate is located. Take a string or measuring tape with a loop end and hook it over the steel pin. Hold the 13 foot mark on the tape or string, and scribe a circle on the ground about the steel pin. Scribe the circle with aerosol athletic field paint.
Setting Out the Foul Lines and Foul Poles
Before we set out the foul lines, you have to know that there are two foul lines running perpendicularly to each other from the corner of the home plate, in the left and right wing. These foul lines also form the baselines for the infield square.
As mentioned previously, the distance or diameter of the outfield from the home plate ranges from 290 to 400 feet depending on the type or size of the field. According to MLB rules, in a 90×90 feet baseball field, the minimum distance of the foul line from the home plate for an outfield is 325 feet.
Taking the MLB minimum distance of 325 feet, that means we have to extend the foul line by [325-90] = 235 feet to the foul pole. So how do we set out this line or extension? We use the 3,4,5 method of setting out which makes use of the Pythagoras theorem. This method is also known as the right-triangle method of setting out.
Since we already have the 2nd and 3rd base of the infield square marked on the ground, we can use these two bases to set out the foul line extension to the pole. Our baseline will be B2-B3 = 90 feet. Drive a wooden stake into the ground on point B3. Take a 300-foot measuring tape with a loop end and hook it on the stake, then roll out and extend the tape to the other end in a linear direction from the existing foul line and stake. Place another stake on point B2. Take another 300-foot tape measure, hook it on the stake and roll out the tape to meet the end of the tape 1. Hold the two tapes on the 235-feet mark with your hands while making sure the tapes are straight, taut and level with the ground. The point where the tapes intersect on the 235-feet mark is where you should place another stake for marking the position of the foul pole (F1). Drive in a wooden stake or peg on this point. Alternatively, you can use a pre-measured nylon stringline to set out the foul line extension. Mark the foul line with aerosol athletic field paint.
Use the same method outlined above to set out the foul line extension on the right side of the home plate. In this case, we will use base B1 and B2 to set out the extension and foul pole (F2).
Setting Up Formwork to Separate Turf and Skinned Areas
As stated previously, a baseball field has skinned areas (clay areas) and green areas (natural grass turf). After setting out profiles and string lines on the field, as well as grading and levelling the site, you have to set up formwork on the ground to separate skinned areas and green areas as shown in the diagram below. Sand or native soil in green areas must not be contaminated by clay in skinned areas, and vice-versa. The formwork can be removed after filling the field with sub-base and rootzone material.
Baseball Field Substructure Filling
A baseball field substructure is much similar to that of a football field, depending on the type of manmade soil profile that you want. There are more than 7 substructure designs for natural grass fields, and what you choose depends on site conditions, climate, terrain, availability of materials, regulations, drainage requirements and budget.
Natural grass fields are divided into three main types which are defined by their rootzone. Sand based natural grass fields make use of a 100% sand rootzone. Amended native soil fields make use of a sand/soil mixture in the ratio 60:40. Native soil fields make use of 100% soil.
A sand-based field is widely used for professional baseball fields because of its excellent surface and sub-surface water drainage characteristics. The sand rootzone, gravel sub-base as well as underground HDPE drainage pipes allow quick and efficient drainage of surface rainwater which percolates into the ground. The water is intercepted by underground perforated drain pipes and emptied into catch basins at strategic positions outside the pitch. Another advantage of a sand-based field is that it can be built flat and level with sea level (at zero gradient) because of its native super drainage qualities. A flat/level surface also makes it easier to set out and grade the levels for the home plate and pitching mound with regards to MLB regulations. However, a sand-based sports field can still be slanted at a gradient of 0.005 to 0.0075 if needs be.
A native soil field with 100% soil rootzone offers the poorest drainage in comparison to sand-based and amended native soil fields. If you are building a natural grass field based on 100% native soil rootzone, you have to improve its drainage capabilities by slanting the field at a gradient of 0.0075 to 0.01 from the pitching mound to all sides.
Building a Sand-Based Natural Grass Field for Professional Level Baseball
Start by digging trenches on the subgrade to lay HDPE underground drain pipes. A suitable drain trench is 400x650mm deep, but the depth depends on the natural water table or aquifer. Perforated drain pipes should be laid at a depth that allows them to intercept underground water for channelling away to a ditch or catchpit. Compact the bottoms of the drain trench and place a layer of sand 32 to 50mm thick. Lay the drain pipes on the sand bed and bury the pipes with gravel filling.
Roll out and lay some geofabric membrane on the compacted subgrade. This membrane can also be placed on the sides and bottoms of the drain trench.
Place some sub-base filling (gravel etc.) on the geofabric membrane. To prevent the gravel and sharp stones from puncturing the membrane, you must first place a layer of sand (32mm thick) on top of the geotextile membrane.
Over the sub-base filling, you shall put some rootzone filling, which is sand in this case.
The top surface of the field will be natural grass, planted as sod, seeds or sprigs.
Installing Baseball Bases and Anchors
A baseball field has three bases in the infield square, and these are the 1st, 2nd and 3rd base. A baseball field corner base detail has two parts, the top cover and a square hollow section steel anchor about 8 inches long, embedded in a concrete base. The top cover is a 15x15x3 inch thick heavy-gauge white rubber cover with a high-density foam interior. A steel stanchion (upright bar) welded on a steel base plate is fixed centrally on the rubber cover. The steel stanchion is a square hollow section steel tube that can fit on the concrete base anchor. So after the concrete base and steel anchor has been installed in the ground, you only need to take the top cover and fit it over the steel anchor. The top cover must be laid level and flush with the ground to avoid the risk of players tripping over the protrusion.
The setting out of foul lines and bases has already been done, complete with stringlines and paint marks, you next task is digging holes for the bases. Dig holes that are slightly wider than 15×15 inches, about 22 to 24 inches wide, and 8.0625 feet deep. Level and compact the bottoms with a tamping rod or rammer, then place a layer of 25 or 30mm sand blinding.
Prepare some square container formwork with an internal width of 15 inches and edges which are 3.5 inches high internally. With a pencil and ruler, draw diagonal lines between opposite corners on the formwork base. The intersection of these diagonal lines is the centre of the base formwork or container. On this centre, you must place the square tube anchor in its vertical position. Make sure that the anchor has its faces parallel to the edges of the formwork base in its central position.
Prepare a concrete mix of 25MPa/19mm strength, then pour the mixture inside the container formwork, spreading the concrete evenly around the steel tube anchor while the anchor is held tightly in position. You will need a steel clamp with long arms to hold the anchor in position. Tamp the wet concrete with a rod to compact and eliminate air bubbles, as well as achieve a slightly flowing consistency. Allow the concrete to set and harden inside the formwork to the required strength before removing the formwork.
Once the concrete has hardened, strip out the formwork, lift the concrete bases by the bottom and place them inside the excavated holes. Position the bases in their right orientation with respect to the foul lines and baselines. The stringlines will be your guide. Make sure that the concrete bases are laid level and at a suitable height from the surface. A minimum surface cover of 0.5 to 0.75 inches is required to cover the top face of the steel tube anchor. When the concrete base is slightly deeper or higher, adjust the level by adding more sand blinding or scrapping away the sand to a thinner layer.
When you are satisfied with the placement and configuration of the concrete bases, you should backfill the holes with soil, compacting the soil in 150mm layers to 95% Mod AASHTO density until you reach the top.
Building the Warning Track
A warning track is 15 feet wide (5m) in MLB regulated fields, and 20 feet wide (6m) in Olympic Game fields. A warning track for the higher age group, collegiate and professional leagues is 15 to 18 feet wide.
The subgrade on which the warning track is to be built must be compacted to 95% Mod AASHTO density with a vibratory roller. The sub-base filling will be different to that under the green turf. As mentioned earlier, rubber surfacing, asphalt and coarse aggregate of particle size less than or equal to 0.375 inches (9.52mm) is often used as a surfacing material on a warning track. The surfacing material is 4 inches deep (100mm), laid over a compacted sub-base course. To handle traffic loads (maintenance vehicles and machinery) over 2 tonnes, you will need to lay a sub-base course 3 to 4 inches thick under the surfacing material. Crushed aggregate with particle size not more than 0.1875 inches (4.76mm) for recreational fields and not more than 0.125 inches (3.17mm) for professional / collegiate fields must be used for sub-base filling. The aggregate is often mixed with a binding material to allow for compaction.
The width cross-section of the warning track must be sloped away from the outfield to the edge of the fence at a gradient of 0.5 to 1.5% towards a perimeter drainage channel with grating and cover. In sports fields for collegiate and professional tournaments, efficient drainage systems that allow for quick surface and subsurface water drainage are installed. On these fields, perforated HDPE underground drainage pipes with outlets to catch basins are laid under the pitch.
Building the Pitching Mound
The pitching mound for a 90×90 feet baseball field has its apex 10 inches (254mm) above the home plate. The pitching mound (also known as the pitching circle) for a 90’ baseball field is 18 feet in diameter, with a radius of 9 feet. The apex or table of the pitching mound is a flat top 60 x 34 inches wide, from which the mound slopes away, from a height of 10 inches down to the circle perimeter which is level with the ground and home plate. The pitching mound table or apex is positioned at a distance of 12 inches (305mm) behind the centreline of the circle on the rear side. The pitching table is part of the footing lane (or footing box), a high traffic area measuring 106 x 60 inches wide inside the circle. The footing lane extends 72 inches in front of the pitching table, on the front side of the circle.
Unfired clay bricks or finely shredded bagged clay is used to build the footing lane because these materials can withstand wearing out caused by high traffic.
Building the Batter’s Boxes, Catcher’s Box and Home Plate in the Home Circle
As explained previously, the home circle is a 26 foot diameter circle containing the left and right batter’s boxes, catcher’s box and rubber home plate. In an MLB regulated 90’ baseball field, the tip of the rubber plate is placed where the left and right foul lines meet. This point of intersection also happens to be the centre of the home circle.
To the right and left of the rubber home plate, a batter’s box 6 x 4 feet ( 1.82 x 1.22 metres) wide is marked 6 inches (0.15 metres) from the side of the home plate. Behind the batter’s boxes and home plate is the catcher’s box, size 8 feet x 43 inches wide (2.44 x 1.09 metres), with has its dimensions extending from the tip of the home plate to the front.
The home plate is a 5-sided rubber with a combined rectangle and triangular shape. The rectangular part is 17 inches x 8.5 inches, and the triangular part has a base of 17 inches and height of 8.5 inches. The overall size of the home plate is 17 x 17 inches wide (432 x 423mm). The Schutt Home Plate (Hollywood Bury-All) is widely used in the United States for professional baseball fields. It comes in black or white rubber with a non-skid surface, cornerless and edgeless construction that prevents cleats or spikes from getting caught on the ground. The rubber is durable and highly resistant to water. The bottom of the rubber plate has a waffle grid that provides a strong and permanent anchor to the ground on which it is installed. The black border around the top surface of the rubber plate ensures that the plate is visible to players. The rubber weighs 24 pounds.
To install the rubber plate, you must first set out stringlines running from the home plate tip to the foul lines (1st and 3rd base) and pitching plate as described in the previous sections of this article. After setting out the stringlines, dig a shallow base which is slightly larger than the home plate. An allowance of 8 inches (200mm) is okay, so your excavated base will be 17+8=25 inches, 25×25 inches wide. Compact the bottom of the excavated base, then add a layer of levelling course such as limestone screening or sand mixed binding material. Compact the levelling course, adding another layer if needed to achieve the required level. Limestone gravel is more compactable than crusher run, that’s why it’s a suitable material for elevating levels.
After levelling and compacting the material, set the rubber plate in position in the ground, ensuring that the sides are slightly touching and aligned with the stringlines. Place a spirit level on top of the rubber plate in both perpendicular directions to ensure that the plate is level with the ground. Backfill the sides of the excavation with excavated soil stored on the site. Compact the backfilling with a tamping rod or rammer, moisturizing the soil if needed and adding more layers of soil until you reach the top. Make final adjustments to the rubber plate, checking its distance from the pitching plate (60.5 feet), and making sure the top face is level and flush with the ground using a spirit level.
Fortifying the Catcher’s and Batter’s Boxes
Just like the footing lane on the pitching mound, the catcher’s and batter’s boxes are high traffic areas which are fortified with unfired clay bricks or finely shredded bagged clay to resist wear by traffic.
Baseball Backstop Installation
MLB rule 1.04 paragraph 4 states that “It is recommended that the distance from home base to the backstop, and from the base lines to the nearest fence, stand or other obstruction on foul territory shall be 60 feet or more”
A backstop is a 20 to 40-feet high fence with Terylene ball stop netting (30x30mm apertures) or chain-link mesh fabric made of PVC / powder coated galvanised steel wires (50x50mm apertures). The backstop as the name suggests is installed behind the home plate and foul lines to stop flying balls from hitting people in the spectator stands. The backstop fence is U or V-shaped running parallel to the baselines (or foullines) at a minimum offset of 60 feet. The fence curve or arc adjacent to the home plate should have a minimum radius of 60 feet from the home plate as well.
A typical backstop has an overall length of 60 to 140 feet depending on its height. A 20-foot high backstop will have a length of 60 feet, while a 30-foot high backstop will have a length of 120 feet.
Backstops can be purchased as standard model systems which are supplied by sports equipment retailers. As an example, SportsEdge has a standard model with a 40-30-40 fence layout and premium model with a 50-40-50 layout, with an option of a 30 or 40-foot high fence. Midwest Netting Solutions LLC has a 4-pole backstop system with a 30-foot high fence, costing USD$32,500.00