Climbing Wall Design
Making a model is the first step in the design process, and the best way to design your climbing wall. The climbing wall model will help refine the details, and help you visualize it. Sometimes a model might show you flaws in your plan, such as joints not meeting up correctly, gaps or overlaps. The model will also help you refine your materials list and cost estimate.
The model helps confirm that your sketch is buildable. You get actual measurements, not just what you think it should be on paper. It helps in calculating quantities, determining sizes and dimensions of your design, and gives you a three dimentional view of your climbing wall plan, and in general helps with the thought process for assembling the climbing wall in the right order. Being able to visualize the steps in assembling the wall helps establishing tool lists, material lists and estimating cost.
Build the model to a scale that is easy to convert to actual size. If you are using feet and inches, a good scale is 1" = 1'. The scale or units of measure are not too important, as long as the model size is easy to work on and visualize.
Adding shapes and protrusions to your wall will make it more interesting and fun to climb. Shapes can be added during the design phase or after the wall is sheeted with plywood using commercial climbing wall volumes, or make your own using scrap.
See Cuting Irregular Shapes for explanation.
Two ways to make a model. You can either make a physical model or a Computer Aided Design (CAD) model. The CAD option gives you the added advantage of being able to take dimentions directly from your 3-d model. Google provides a free CAD modeling program called Sketchup. There are other free CAD modeling programs available. You don't need to make both the physical and CAD models. Just choose one type of model to make. For this example I made both just to show it. If you are proficient with CAD that's the type I recommend. You can dimension directly on your CAD model and get bevels, angles, distances, etc directly from your CAD model.
Physical Model.This model is made of cardboard. Cardboard won't give you accurate dimensions, but I did learn two important things from the cardboard model. First, I initially estimated 10 sheets of plywood. However when I made the cardboard model I discovered by re-using left-over pieces I could make the wall sith 6 sheets of plywood. Second, as I was assembling the model I could see and visualize that there would not be enough overhang--so on the cardboard I increased the top overhang by one foot for all sections. This is the value of a model... you visualize the 3-d wall and make adjustments to the planning phase's sketch.
CAD Model The CAD option gives you the added advantage of being able to take dimentions directly from your 3-d model. Plus you can design the back supporting structures. With CAD you can design your model to exactly fit the space you have available, mark where ceiling joists are located, decide how to anchor and support the wall, and dimention directly on your CAD model. With CAD you can accurately account for stud and plywood thickness.
There are different types of plywood.
- Particle Board is not good for climbing wall construction. It is made from sawdust and other small pieces and chips of wood and glued together then pressed with high pressure into sheets. Not strong enough for climbing walls.
- Medium Density Fiberboard (MDF) also not good for climbing wall construction. This type of plywood is made from individual wood fibres rather than sawdust. MDF is stronger than particle board but it is not strong enough for a climbing wall.
- Oriented Strandboard (OSB) In terms of construction material it is considered equal to plywood. It is made of layers upon layers, about 50, of wood strands. OSB costs less than plywood. Depending on the area you live in it could be from 30% to 50% less expensive. While it is considered an equivalent material to plywood for construction there are differences which make it less desirable than plywood for a climbing wall. Some people say it can be used for climbing wall construction. I think there are enough disadvantages to OSB to justify paying a little more for 5/8" plywood.
- Plywood. Plywood is made from several thin layers of wood veneer. The layers alternate in direction by 90 degrees. This makes it's sheer strength very high, reduces splitting when screwed or nailed, and reduces swelling or shrinking due to moisture and temperature changes and therefore better dimensioning.
If you are considering using OSB - First read Plywood vs OSB for Climbing Walls. In my opinion, all things considered, it's better to use 5/8" plywood for climbing wall construction, not OSB.
Dimention everything. Whether you use a physical drawing and model, or a CAD model, dimention everyting and verify they add up to the width of the wall, not more. Do the same thing vertically. Allow a little gap between plywood sheets, about an 1/8th inch or 3 mm, between sheets to allow for expansion and contraction.
As you dimension your wall account for the actual thickness. Lumber is designated by its nominal value. The finished size of a 2 x 4 is actually 1 1/2 inches by 3 1/2 inches.
Plywood also has a nominal thicknesses, but the actual difference is very slight. Plywood is typically only 1/32” thinner than it's nominal value.
3/4 x 3 1/2
3/4 x 5 1/2
3/4 x 7 1/4
3/4 x 9 1/4
3/4 x 11 1/4
1 x 1 1/2
1 x 3 1/2
1 x 5 1/2
1 x 7 1/4
1 x 9 1/4
1 x 11 1/4
Nominal Size and Actual Size.
The designated size of US lumber is not the same size as its actual thickness. US lumber is designated by its nominal value, or the size of the lumber before finishing. Remember that the actual size and nominal size are different dimensions. Be sure to account for the difference in finished size while you are defining your dimensions.
The nominal size is the unfinished size. Wood is first cut into the nominal size. In the US, lumber is planed and sanded after it is cut at the mill. This takes off a quarter inch to a half-inch.
The actual size is the size of the lumber as it is sold. For example, using the table above, a 2x4 measures 1-½" by 3-½" actual size. Plywood nominal size and actual thickness are the same.
Joist Span for Climbing Wall Design Considerations.
For overhanging sections, the allowable joist span length depends on the spacing and size of the joist. According to the table below, using 2x6 construction you can safely span an 8' length with either 16" or 24" OC. For greater span lengths you will need to use a larger joists.
Support Structures for Climbing Wall Designs.
Climbing walls are very heavy. The structure that supports the wall must be strong enough to support the dead loads (the weight of the wall itself) and live loads (the climbers). The dead loads alone will come to several hundred pounds. Live loads vary not only by the weight of the climber, but also by the momentary weight forces caused by the climbing moves. These forces can be several times the weight of the climber. The support system must be capable of supporting the maximum combined stresses. If you are using an existing structure to support your wall, make sure the existing structure can also support these loads. A vertical or near vertical wall will transfer most of the weight to the floor, however will still exert an angular force away from the wall due to the climber(s). Steeply overhung and roof sections must be capable of supporting the combined weights of the wall, climbers and weights from the momentary forces caused by a climbers movement. Again, get advice from experts and industry specialists.
The size of joists, studs, anchors are determined by the load the wall must bear. Determine how each end of each type of material will attach to another piece. Determine that the existing structure is strong enough to hold itself up and can withstand the stress from climbers. Be sure to get advice from someone knowledgeable in structural design. This is very important if your wall has overhanging sections. A vertical or near vertical wall will have a lot of vertical strength from the plywood. Make sure you have supports to withstand shear, torque and live load stresses. You must take responsibility to ensure engineering considerations are done correctly. Consult with experts and get advice.
The last step is to develop the bill of materials based on the specifications in your design. Go back over your drawing item by item and write them down. Determine specific quantities of each type of material.
Simplicity of Design. A complex design may require additional support structure, may take longer to build, and adds much more potential for errors in design or construction, all of which drive costs up. A straightforward design that is easy to understand and build will be the most cost effective—as long as it meets your needs.
Save some money on materials. When you’re at the lumberyard, ask to check out the cull bin. A cull bin is a collection of scraps that lumberyards may sell at significantly reduced prices. Usually these scraps are high-quality lumber pieces that are marked down simply due to their odd sizes.