My son has outgrown his pitching mound so I decided to build another one. He's just starting his Freshman year so I know he will still be growing and we will get at least another 4 years out of this one. The mound has to be sturdy and weatherproof. Mobility is not an issue as we will not be moving this one around. I
Step 1: Base
I decided to use a piece of 4' x 8' treated plywood as the main part of the mound. For the base, I started with 4 1" x 10" x 10' pine boards. The upper part of the mound - I'll call it the upper base - is 20" deep and 4' wide. Subsequently, I made a mark at 20" on the pine board and drew a line to the end, stopping at 2". See photo.
Step 2: Bracing
I used a lot of scrap pieces to brace the 1" x 10"'s - probably overkill but I wanted to make sure nothing moves.
Step 3: Top Sheet
I added the 4' x 8' sheet of treated plywood, securing with drywall screws. Make sure your base is exactly square prior to securing the plywood. I soaked all pine boards with Thompson's water seal prior to securing the plywood.
Step 4: Add Turf
I had a large piece of high-quality turf that I decided to use for the covering. I used carpet adhesive and staples to secure. I was about 12" short so I bought a piece from Menards. To finish, I added an old pitching rubber. The mound is solid with any pitching movement.