Framing and Anchor Design: Part 2
Framing the wall
The framing of each section of the wall is shown in Figure 4. Notice that each section, the vertical section and the overhanging section, are both 4'x10'. Since plywood is generally only sold in 4'x8' sheets, you will need some extra ply to sheath the extra 2'x4' section of the overhanging frame on either the top or bottom. We recommend the bottom as it can be used as part of the kicker plate. When screwing your frame together, use 2 1/2" #8 decking screws and wood glue at each joint. Pre-drilling the holes appropriately will aid in driving the deck screws into the framing.
When framing each section, be sure to square up the frame using a framing square before driving the screws. It can be helpful to tack the frame together with some nails to hold it all together while you square the frame. This is the only time nails should be used in the wall's construction. If your frame is not square, it will not anchor properly to the wall stud anchor points and your plywood will not lay flush over the frame.
Another important aspect of the framing is the 14.5" O.C. frame studs on the inside of each section (see Figure 4). The reason they are not at the standard 16" O.C. is that they will both share the 4th wall stud as explained earlier. For a conceptual understanding of what this will look like when anchored to the wall studs, see Figure 5 below. Note: Do not attach the plywood to the frame until the framing is complete and the wall has been anchored to the studs. If you do, you will not be able to anchor each section to the wall studs. You need to be able to get at all anchor points behind the wall. Therefore, the plywood should be attached to the framing last.
Anchoring the frame to the wall studs
Once you have framed each section of the wall and verified that each anchor point lines up properly, you are ready to attach each section to the wall studs. To attach your framing to the wall studs, you should use 1/2" carriage bolts of at least 4" long. For the anchor points on the 4th stud, you will need 6" carriage bolts to go through the stud and both sets of braces (see Figure 5). Attach all the plywood braces to the wall studs first and insert a carriage bolt through the wall studs and braces as shown. Do not tighten them completely...just snug them finger tight for now.
With the help of a friend, lift the frame of the first section into place and insert another carriage bolt through the braces and the pre-drilled anchor holes in the wall's frame. Tighten everything up with a socket wrench. Repeat for the overhanging section using the longer braces shown in Figure 3.
Attaching the plywood to the framing
When drilling your 7/16" holes for the t-nuts, there are two schools of thought regarding their position on the plywood. The first is drilling in a grid pattern. The advantages of a grid pattern is you know exactly where the holes will go in relation to the wall's framing. If using a grid pattern, start your grid 4" in from the perimeter of the plywood so you don't contact any framing studs, then drill your holes on an 8" grid. This will get you about 72 holds per sheet. For less holds, mark out your grid at 10" or even 12" depending on how many holds you want.
While the grid pattern is the most commonly used, random placement of the t-nuts is also an option. Randomly spaced holds make things a bit more interesting, but you run the risk of drilling holes too close together and even over the framing studs behind the wall, which is a bummer when you try and thread a bolt into the t-nut. A note about drilling the t-nut holes: Always drill the 7/16" t-nut holes from the climbing side of the plywood, and be careful when drilling to avoid splintering the back side of the plywood. This splintering may cause the t-nuts to not seat properly when hammered into the holes which compromises the strength of that t-nut location. The last thing you want is for a t-nut to rip through the splintered hole when you're pulling on that huge jug. To avoid this splintering, simply place some scrap wood under the plywood sheet when drilling your t-nut holes.
Once you have drilled all the 7/16" t-nut holes, it's time to insert the t-nuts into the back of the plywood. The t-nuts have an outside diameter of 7/16" (that's good, since that's the diameter of the holes you just drilled) and an inside diameter of 3/8". Lay the plywood sheets down backside up and hammer in a t-nut into each drilled hole. Be sure to hammer the t-nuts as straight as possible so they seat properly. Once all the t-nuts have been banged home, you can then attach the plywood to the framing. Use 2 1/2" #8 decking screws spaced about 12" - 16" apart.
Attach your climbing holds to your new wall using the appropriate bolt/screw combination. Be sure to avoid overtightening the bolts! Plastic climbing holds can break if overtightened. You want the hold to be snug enough so it doesn't spin, and go another partial turn with the wrench. The amount of force required to secure the holds to the wall is an acquired feel. Check all holds periodically and tighten those that spin or seem loose. Retire any damaged holds to avoid potential injury.
Have fun on your new climbing wall!