Don't forget the springs.
Altho the joists are likely not to be in mortal danger from springless-ness,
you might induce wall/ceiling cracks from this kind of percussive load.
Along those lines, consider matting/padding on the attic floor, to dampen
the percussive loads of all the inevitable jumping around. Sam's/Costco
have a kind of rubber-interlocking colored matting, relatively cheap, altho
I think multiple layers of thick-pile carpeting would do well also.
Another and perhaps better strategy is to take plywood/floorboards raised up
on 2x4s (wide-side down, if you prefer), but deliberately spaced wide so
that the wood has some spring to it.
An even more elegant strategy, and not that complicated, is to create a
"floating floor", with supporting 2x4s (mini floor joists, if you will,
traditionally spaced) mounted on die springs. Then carpet this. Splinters,
I use a variant of this system for weight lifting, for shock absorption of
the lowered bar/weights. *Very*
effective, perty elegant.
The 2x4s would actually be drilled to accept the die springs. Easy to do.
Die springs for this application would run between $3 and $5 each, you might
need about 4-8, depending on the area around the bag.
Unfortunately, some experimentation w/ spring length and stiffness will
likely be required. Most likely the springs I use for my weight ditty would
not be optimal for your floor, but they would still work.
Some hardware stores (mebbe even goddamm HD) have a nice selection "stock
springs", some of which are pretty heavy duty, and might suffice for this
application. You're looking at springs approx. 1" in diam, 2-4" long, with
a wire size of about 1/8"--perty thick, for spring wire.
If you decide to go this route, I can help you experimentally determine the
working spring size,without it costing you a fortune.
And, a nice hardware guy would let you return the springs you don't use, if
you tell him up front what you're trying to do.
Which is perhaps the only redeeming thing about goddamm HD, returning crap
w/ impunity. :)
Other substitutes exist: urethane springs/pads, HVAC isolation pads, often
made out of rubber/cork, etc.
Much more than you wanted to know, I'm sure. :)
Mr. P.V.\'d (formerly Droll Troll), Yonkers, NY
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