QUESTION: This isn't so much a home improvement project. I wanted to build a modest but very durable exercise bench. I've seen some DIY videos online and I feel uncomfortable with how much weight they might hold. I was thinking maybe just put 9 or 12 4x4s together in a stack that is wide enough to lay on and cut long enough for ones hips to head and somehow nail them all together in a super secure way. Maybe even add a handle to drag it around. Any ideas? I don't know how much that might end up costing but I assume putting no space between the wood would make it good for lifting nearly any weight. Ideas?
ANSWER: Hi James, think of a common picnic table; the braces that support the bench seat are about 4'to 5' apart and they are usually 2"X 12" or 2" X 10" boards laying flat. Two adults weighing between 350 to 400 pounds combined can sit on that bench and it won't break.
A residential floor constructed with 2x4s on end spaced as much as 24" apart and only five feet long is strong enough to handle 60 pounds per sq. ft. If your bench is 5' long and 18" wide that results in a weight bearing structure of 7.5 sq. ft., or 450 pounds total. Now space the 2x4s only 3" apart and you could park your car on it and it wouldn't break.
Here is a way to connect it all; take seven 5' long 2x4s and drill a 1/2" hole dead center of the 3 1/2" face at the 1', 2 1/2' and 4' mark. Use that 2x4 as your pattern then clamp each of the remaining six 2x4s, one by one to the pattern and drill the same three holes in of the 2x4s. Next cut 2x4s into 6" lengths and drill a 1/2" hole dead center in each and align them with the holes in the 5' 2x4s and nail them in place. Use a dowel to keep the 6" piece in place while you nail it with an appropriate size nail (12d) Now line up all of these assemblies and insert a 1/2" all-thread cut to the appropriate length and secure the whole assembly with counter sunk washers and nuts on each end of the three rods. This structure will be extremely strong but not too heavy. If you don't like the idea of having open spaces on the bench surface than simply use 13 5' 2x4s and skip the 6" pieces and do the same drilling and placement of all-thread.
However you decide to support the bench be sure adequate bracing is applied to prevent racking in any direction. Good luck.
Wood House Log Homes LLC
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QUESTION: I'm not terribly familiar with building materials or what "racking" means. I am having trouble visualizing what you just said. I think 500lbs support is enough and maybe 2.25x width a picnic table bench would be broad enough. Any other way you can put it? What types of wood also? The price seems to vary quite a bit.
James, send me an email at firstname.lastname@example.org and I'll reply with a simple sketch.
Racking is, in essence, collapsing sideways. It occurs when a weight supported by posts, or a typical frame wall of a house has no cross bracing or sheathing attached firmly to the posts and a lateral force is applied, such as a seismic tremor, wind, or other sideways pressure. Although the posts or wall can support the weight so it doesn't drop straight down a lateral force can topple the whole structure like a house of cards.
Send an email and I'll sent a sketch of the bench and an example of a racking situation as well as how to brace to prevent racking.
Wood House Log Homes LLC