Can anyone tell me what rubber to ask for?

Heres my rooms materials list for the weight: 90 x 35mm dry framing 150lm 90 x 45mm dry framing 50lm 23mm gysym board 42m2 R1.8 75mm insulation 42m2 100mm noise batts 100mm 42m2 20mm flooring 9m2 Anyone have any idea what kinda rubber to float the floors I need to ask for. Thanks JohnG

John, first off can you click on your profile and put a location down? I get tired of trying to remember where everyone is located, and answers aren't the same in all parts of the world - Second, is that the TOTAL amount of material you will be floating on rubber? Here is most of the info you need to figure out your specific application, except for some of the weights - http://www.johnlsayers.com/phpBB2/viewtopic.php?t=839 There is both a method and some weights there - for your 23mm wallboard, just double the weight of the 1/2" gypsum. For the lumber - 460 cubic inches of wood weighs roughly 8 pounds, since its specific gravity runs between .50 and .55 for most species - so a 2x4, which is really 1.5" x 3.5", runs 206.6 cubic inches per meter - dividing 460 by 206 shows that a meter length of 2x4 would weigh roughly 2.2 pounds, or almost exactly 1 kG. Check out that link, and if it gets too difficult to figure out come on back - Regardless of what size and spacing you end up with, 1/2" EPDM rubber (60 Durometer hardness) is your best (not cheapest) bet for floor floating - typical life of 25 years compared to about 10 years for neoprene. Re-read the rest of that thread I linked to if you get time, there's quite a bit more there than just floors... Steve

Thanks Steve Profile updated JohnG

If you can't pay regular high prices for EPDM, you can go to your local roofer and get scraps for a lot less. We did that, then cut the stuff into appropriate strips with a small pair of metal snips, stacked them up until we got the requisite half inch, and put them where needed. Aside from price, the advantage is that you can cut them to fit the situation. e.g. Under wall plates, we cut them the width of the plates so they don't wobble.

Thank's guys. Interesting point - I talked to quite a few rubber suppliers down here about EPDM verse Neopreane verse "natural" and they all say as long as the hardness factor is the same (60 or so) they will do the same job. Apparantlly because the rubber is not exposed to UV (under floor/walls) then all types will last equally as long. EPDM and, to a lesser extent Neopreane, in there humble opinions are a total overkill when plan old natural rubber will do the same job and last just as long.

They're not taking into account the load that will be constantly applied to the rubber, nor the fact that it still has to act as a spring after 10 years of static loading - try asking them how many studio floors they've floated with the stuff, and how many still isolate as good 15-20 years later - If necessary, talk to Jeff Szymanski (chief acoustic engineer at Auralex) and ask him if they would have chosen the more expensive EPDM for their U-boat isolators if they could have charged the same for a cheaper formulation - Aside from that, yes - initially, 60 Duro rubber of ANY kind should work the same. The difference is, for how long? Steve

Get what you pay for I suppose Steve. JohnG

Yeah, if you're careful - :? I just want to make it clear for you so you don't expect more than you get... Steve