Introduction: Outdoor Weightlifting Platform
This Instructable will show you how to build an 8’x8’ outdoor weightlifting platform.
1 - 1-3/8-in woodboring tri-flute drill bit
10’ - 1” sch 40 galvanized steel plumbing pipe
2’ - 3/4” EMT conduit
2 - 3/8” x 6” galvanized carriage bolts
2- 3/8" galvanized nuts
2- 3/8" galvanized washers
4 - 4” x 5/8” galvanized lag bolts
6 - 5/8” galvanized washers
2 - 12” x 5/8” galvanized bolts
2 - 5/8” galvanized nuts
6 lbs - 3 1/2” deck screws
1 lb - 2 1/2” deck screws
28 - 2x6x8 pressure-treated (PT) boards
2 - 6x6x12’ PT posts
1 - 3/4” 4x8 PT plywood
12 - Concrete deck blocks
500 lbs of gravel
4- 50 lb bags of fast set concrete
2- 4’x6’ rubber horse stall mats (Tractor Supply)
Step 1: Set Posts
Clear and level a space a little larger than your platform. Use stakes or marking paint to outline the platform. Mark the holes for the posts 18” from the front of the platform to leave room for a spotter and 44” apart on center (OC). I rented an auger with a 10” bit and dug 3’ deep. Add a few inches of gravel to allow for drainage, insert the post, then plum and brace with scrap 2x4s. I used 100lbs of fast set concrete per post and let it set overnight.
Step 2: Lay the Foundation
Mark off the locations of each deck pier. My back yard has a 10” slope over 8’ so I dug the first row of deck piers 5” deep and built up the back row 5”. Spread at least 2” of gravel under each deck pier and compact the ground. Level each block as you go. To aid water runoff, I added a slight slope (1” over 8’). Add landscaping fabric to prevent weed growth.
Step 3: Build Frame
This plan is designed to support a 2,500 lb hot tub so the 2x6 joists are 12” apart. Cut 7 boards to 93” and use 2, 3-1/2” screws to attach each joist to the rims. Use joists hangers and 2-1/2” screws to attach the joist to the posts.
Step 4: Install the Deck Boards
Layout your deck boards before you fasten them. I found several of my boards were more or less than 8' in length. By laying the boards out first I was able to arrange them so the shorter boards were not as noticeable. Fasten the boards with 2, 3 1/2 inch screws at each joist.
Step 5: Install the Pull Up Bar
Mark the height where you want your pull up bar and drill all the way through the first post using a 1 3/8" bit. For the second hole, you only need to drill halfway through the post. Cut the pipe to size using an angle grinder then slide it in place. Drill a 1/2" hole through the posts and pipe and secure with a 3/8" bolt, washer, and nut. After burning through several drill bits, I ended up buying a tungsten carbide step drill bit to bore through the pipe.
Step 6: Install Plywood and Horse Stall Mats
Mark off and cut notches in the plywood to fit around the posts using an oscillating tool or jigsaw. Secure plywood in place using 2 1/2” deck screws. Cut the horse stall mats to size using a straight edge and razor. You need to make a scoring cut then go gradually deeper with multiple passes with the razor. I cut one mat in half long ways making two 2' x 6' strips. I cut 2' off the second mat short ways then cut that in half again which left me two 2' x 2' squares a 4' x 4' remnant. Use the same method to notch the mats around your posts. You can secure the mats with deck screws but I found the weight of the mats keeps them in place.
Step 7: Install Racking Pins
Get someone to help you mark the various heights for the racking pins. You want the pins a little lower than where the bar sits on your shoulder for squats. I marked holes for squats, incline bench presses, flat bench presses, floor presses, and one with the bar resting on my chest as a safety. Drill 1/2" holes for the lag screws and 3/4" holes for the bolts. Cut your conduit into 1" sections for each racking pin and 6" sections for the safety bar. Add a washer, your conduit spacer, and then insert the bolt. Secure the bolt with another washer and nut. Just hand tighten the nuts so you can remove it if needed.
Note: I used 5/8" lag screws because I had them leftover from another project. However, If you use 5/8" bolts and nuts you could move the pins to different heights.
Step 8: Weight Tree
With the extra 1" pipe I made a weight tree. I cut down the pipe into 12" sections, drilled 3/4 of the way through the 4x4 fence post, and inserted the pipe. The weight of the plate holds the pipe in place, but you could drill through the post and pipe then secure it with a screw or bolt.
Step 9: Links
Here are the plans to build the weight bench, concrete dumbells, and concrete plates.
Adjustable weight bench:
Step 10: Seal
Thanks to a great suggestion from MattDoesThat, I sealed the platform to protect it from the elements. Once the lumber has dried out and absorbs water it can be sealed. If needed, pressure-wash the platform (I recruited my son to do it 😉).
After letting the wood dry overnight, we used Cabot Australian Timber Oil (Natural) to seal the wood. I chose Cabot because of how well it did on moisture protection in The Great Stain Shootout We brushed the sealer on the posts and used a lambswool stain pad for the floor. The timber oil looks great and water beads up nicely now!