IIC Ratings
Q: I am wondering how to add IIC ratings for two different materials, as I know that I can’t simply “add” them together for the total score.
I am meeting a lot of resistance in my condo regarding installing wood floors because of noise issues. I found an ASTN test result that tested a similar carpet & pad to what was originally in the unit for an IIC rating of 54. If I use an underlayment that has an IIC of 58, would that number be reduced when coupled with the engineered hardwood floating floor that will be installed over it?
I can find IIC testing for carpet/pad systems, but no test conducted with actual wood *over* the underlayment, so I’m not sure what the IIC rating would be for the overall system!
Is there a mathematical way to determine what the overall IIC rating would be for my flooring system? Also, is the difference typically audible, compared to carpet, if one doesn’t wear shoes?
Hope you can help me!
Alia
A: Most IIC ratings for wood flooring underlayment is calculated with a layer of 5/8″ bare plywood laid over the top of the underlayment to act as a pseudo floor. This means the ratings should be pretty accurate to what you will get with a finished floor over the underlayment. The primary difference you get between carpet and hard surface flooring is that your feet impact the hard surface first with a wood floor, where as with carpet that impact is cushioned before hitting the subfloor’s hard surface.
If you choose to not wear shoes over a wood floor there will be an audible difference in your condo, but overall the impact transfer should be roughly the same going to other units. If you want the room itself to sound quieter, walk around in socks and it will reduce sound quite a bit. This is especially the case with high heeled shoes as they are very noisy over wood floors and can cause denting, so avoid wearing them when possible. Overall, if you have concerns about your condo board, you could combine underlayments, such as using 6mm and 3mm cork or 6mm cork and sound 6, but typically this is overkill for most condos and 6mm cork tends to be enough or various other underlayments out there which are denser modified-foams or rubber.