mikeklooster wrote:If we are both going to use this alternative maybe we should buy together, and anyone else whos in the market right now.
I agree -- in fact, this is an area where our
Northern California Gang of Studio Construction Wannabes might be beneficial -- perhaps we could co-op some of our purchases.
So, here's the latest on my existing garage floor situation.
Today I spoke with a very knowledgeable manager at the concrete company that did the concrete work in my house. He said that his recollection of my subdivision is that they used
4" thick concrete atop a (minimum) 2" rock base with a 6" x 6" wire mesh for the initial phases (which includes my house), but that later phases may have upgraded to rebar.
He siad the mix was designed at 3,000 psi, but that over time my floor hardened to at least 5,000 psi.
He also said that he would not recommend more than
10,000 pounds of total weight for my room without consulting a geotechnical engineer. (Obviously, with 6,000 pounds of walls of 2,000 pounds of ceiling, an 11,000 floating floor won't fly on his word alone.)
I called one of the geotechnical engineering companies he recommended. That gentleman said a 3,000 psi mix is "pretty darn good" because most are 2,500. He estimates that my concrete floor can withstand up to
250 psf.
Bear in mind that this means, but recommended that I consult the structural engineer who worked on my subdivision.
I called the builder and obtained the name and phone number of the structural engineer. I just left voice mail over there.
So, let's do the math on what we know so far: Multiplying 250 (the psf estimate) by the square footage of the footprint of my floating floor (roughly 9' x 15') is 33,750. That's good. However, that would assume 100% contact between the floating floor and the existing concrete, which is not correct -- the RIM system has 2" square pucks on 24" centers. That means there is only 1 square inch of contact for each square foot of floating floor. That's the equivalent of about 126 square
inches of weight transfer area, scattered around.
Hopefully I'll get my voice mail returned with some assurances that I'm looking for -- or, I'll learn that this thing is just way too heavy for my existing floor.
Or, perhaps a
steel plate lying underneath the RIM system will help distribute the weight of the blocks over the concrete floor... But that may be problematic from an acoustical standpoint.
mikeklooster wrote:dan hornac from tempco(kinetics). . . was quite at ease with the weight factors. . . It just seems wierd that every body here is so cautios and thorough yet the product saleman isnt worried at all.
Well, I just got off the phone with him. We spoke for over 20 minutes. He said he didn't know much about construction and engineering and that "you'll have to consult with your building and engineering experts" regarding the weight limits of my existing floor.
Perhaps he misunderstood your "weight factor" concerns, thinking the concern was overloading the Kinetics product, rather than overloading your existing concrete.
I found this interesting tidbit:
Portland Cement Association wrote:What is 3,000 pound concrete?
It is concrete that is strong enough to carry a compressive stress of 3,000 psi (20.7 MPa) at 28 days. Concrete may be specified at other strengths as well. Conventional concrete has strengths of 7,000 psi or less; concrete with strengths between 7,000 and 14,500 psi is considered high-strength concrete.
(Source)
I just posted at
Eng-Tips Forums -- hopefully I won't get tarred and feathered for crashing their party!
Hope it turns out ok.
...but I'll owe you big-time gratitude when I'm done with my room and my slab is still in one piece! 
