There are many people in this world that have their own private vocal booth in their home, an area to play the drums, or they are building things like risers in home theaters or other platforms that will be used for amps, speakers, etc.  Placing drum sets, speakers, amps, and similar items directly on the sub-floor can cause serious problems when it comes to sound transfer through floors and throughout structures.  Depending on where you live you may really be pissing off the neighbors!  There are several ways to successfully build a platform or similar floating floors, but in this article we will discuss a cheap and effective way of isolating a platform from an existing floor.

First Step: Build the Platform

Regardless of the sound isolation products you use, you will need to build a platform that is independent of the existing framing.  These platforms are typically built using 2″ x 4″  framing with 16″ on center spacing or 24″ on center spacing.  The less connection points that one material has with another the better the performance in sound isolation.  So 24″ on center is recommended, but when the platform is under 70 square feet then spacing really won’t make much of a difference at all.  The basic construction of the platform is shown in the gallery below.  Build a box frame using 2″ x 4″ studs and then connect studs 16″ oc or 24″ oc within the box.  Top this frame off with a minimum of one layer of 1/2″ or thicker sub-floor material.

Second Step: Add Something Beneath the Platform

Here’s where you have a few options:

Joist Isolators

Joist Isolators are U-shaped rubber pieces that friction fit on the bottom side of 2″ x wood products usually either 2″ x 4″ or 2″ x 6″ joists.  Using this product is cheap, simple, and depending on how much sound you need to isolate it may be effective enough to be the only sound isolation product you use if you want to keep the budget down for your floor.  A quick way to estimate the number of joist isolators needed is to take your total square footage and multiply by .65.  The smaller the area, the less likely that number will work so sometimes it is just better to draw the platform out and count how many you will need.  For small platforms you can space the joists 24″ on center, but for larger areas you will want to space the joists 16″ on center to help stabilize this floating floor design.  From there you will need one isolator on each end of the joist and then every 2′ in between.   As you can probably see if you have a platform that is only 6′ x 6′ then you will only need as few as 24 joist isolators to complete the job.  Joist isolators should be installed on hard surfaces so using this product over existing carpet will be pretty ineffective unless you were to first lay down a layer of sub-floor before setting up the joist isolator and platform system.

GenieMat RST Rubber Underlayment

Recycled rubber underlayment is another option and typically the most common option because rubber underlayment can be applied in layers making it thicker than a regular joist isolator and because it is a more resilient product than joist isolators are.  The durometer (hardness level) of recycled rubber underlayment is almost half of what a standard joist isolator is.  Installation for this option is simple and is also pictured below.  Measure your total square footage to make sure you have enough GenieMat RST, cut the underlayment to size so it fits beneath the platform you create, and then lay it down on the floor before you place the platform.  The underlayment must cover the entire bottom side of the platform so that no part of the platform comes in direct contact with the floor.  Multiple layers of underlayment will improve performance (two layers of RST-05 is better than 1 layer of RST-10 even though the overall thickness is the same). Since the area you are covering is so small and underlayment typically only comes in 4′ x 15′ or 4′ x 30′ rolls we suggest using what you got.  :)

UPDATE: GenieMat FF Modular

Since this article was written, the creators of GenieMat RST have introduced a new product to their line called GenieMat FF Modular. The performance of this product would far surpass the GenieMat RST option described above and the case study below. The concept is the same, but with a pre-built modular design. If your structure is wood-based, then we would suggest adding either 7 pounds per square foot of material below or above the FF Modular. This mass can be from plywood, OSB, MDF, Hardibacker, etc. If your structure is concrete then you can install the GenieMat FF Modular directly to the sub-floor.

Other Options

You can add other products below this platform as well.  There are thick gym mat products, mass loaded vinyl (MLV), thick cork (6mm+),  and other ‘sound board’ type products that you can use.  We recommend the two options above over anything else because of the resiliency of rubber cannot be beat.  Dealing with deep vibrations you will need something resilient beneath the platform so the use of rubber is always recommended.  A thick gym mat can provide some decent results, but the mat will need to be over an inch thick which makes for a sometimes too cushy of an underlayment.

Third Step: Add Something On Top Of the Platform

To minimize costs you can avoid this third step.  This of course assuming you have chosen to use either joist isolators or rubber underlayment as discussed in the second step.  Like the bottom side, there are several options for the top side of this platform.  Here are a few that we recommend:

Rubber Underlayment

Rubber underlayment is superior at dealing with structure-borne noise so it is a great option for the underlayment that you install on top of the platform.  Like the bottom side, cut the underlayment to fit covering the entire top of the platform.  Multiple layers in this situation is always better than one layer so make sure to get enough!  Something thick like a 1/4″ rubber underlayment is always preferred to a 2mm or 3mm underlayment.  The rubber underlayment does not need to be attached to the top of the platform in any way.  To finish off the design you can lay a section of carpet over the platform and attach to the sides of the platform or just leave the underlayment as it is uncovered.

Mass Loaded Vinyl

A quality barrier will perform very well in this situation and since you are covering such a small area we recommend thickening up that barrier going with a 2 LB MLV over the more common 1 LB MLV.  The 2 LB MLV is as thick as one layer of GenieMat RST-05 rubber underlayment, but you do have the added weight with the 2 LB MLV which will help isolate more airborne noise than the GenieMat RST can.  The cost for the 2 LB MLV is a little more than GenieMat RST and if you layer the GenieMat RST then the 2 LB MLV will not perform better than the GenieMat RST.  But as a single layer underlayment, the 2 LB MLV is quite a performer!

Green Glue

The most popular sound isolation product online is without a doubt Green Glue Compound.  To use Green Glue in this situation you will need a second layer of sub-floor screwed to the existing layer on top of the platform with Green Glue applied at a rate of either 2 tubes per 4′ x 8′ sheet or 3 tubes per 4′ x 8′ sheet.  This system will add a decent amount of mass from the extra layer of sub-floor and also the most damping that any product can provide between the two layers of sub-floor.  Performance for this option should be very similar to the GenieMat RST and 2 LB MLV options discussed above and also be very competitive in overall price as well.  The only drawback is if you add a second, permanent layer of sub-floor to your platform then it will become pretty difficult to move the platform if you ever need to.  If your platform is going to stay put for as long as you have it then this is of course not a problem.

Case Study

We had a customer in Minneapolis that likes to drum on an electric drum set in his apartment.  The only noise he really generated was the sound of the drumstick against the drum pads.  This sound was transferring directly to the neighbor’s below and he was receiving complaints about this.  So he contacted us to find a solution and the pictures below were taken by him showing what he had done and the final results.  Here is a quote from him about what he did and his results:

The GenieMat RST-05 is working great!  I built a 5′ x 4′ platform out of 2″x4″s and a 0.5″ plywood sheet on top.  Since I didn’t want any of the roll to go to waste, I put two layers of the GenieMat RST-05 between my carpet and platform, three layers on top of the platform, and some stock carpet on top of everything.

I have been rocking out pretty hard for some time now, and I haven’t heard a word from my floor neighbor.  I even contacted her and asked her to call me if there were ever any problems with the noise. Still nothing!  I could have probably used less than 5 layers of the GenieMat RST-05 to do the job, but I haven’t had any complaints so I have no reason to change the setup.  Thanks for the suggestion for building the platform by the way, I think that was key to isolating the sound.

Conclusion

Isolating sound transfer in a small area can be very simple and cost effective.  It also makes for a fun weekend DIY project–if you are in to that sort of thing!  With a basic platform and some sound isolation products beneath the platform and/or on top of the platform you will notice some dramatic results with minimal cost.  It is always recommended to treat the entire room rather than just the direct area that the sound is transferring through, but quite a bit of sound will want to flank through your floors so a simple platform will still reduce a serious amount of sound.

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