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IsoJoist, also referred to as joist isolators or stud isolators, are two inch wide pieces of EPDM rubber U-channel designed to soften the connection between 2x4 or 2x6 framing members and typically a sub-floor. IsoJoist is installed by friction fit and requires no permanent attachment to the sub-floor below or the joist that rests inside the IsoJoist. Typically an IsoJoist is used in floating floor construction for platforms, home theater risers, recording booth floors, or even entire rooms. This product cannot be used as a decoupler between studs/joists and drywall on walls and ceilings. To decouple a ceiling or wall you must use resilient sound clips, a room within a room design, or resilient channel.
For quick estimating based on square footage over a large area, estimate 1 IsoJoist per square foot (e.g. 100 IsoJoists per 100 square feet of floor).
For estimating to the exact number of IsoJoists required for your floor, plan for 7 IsoJoists per 8' linear feet of joist (assuming 8' long joists are used). Typically for lengths shorter than full 8' joists estimating can be accomplished by dividing the total linear inches of the joist by 16 and then add 1 to that number (i.e. for a 4'8" joist, multiply 4 x 12 and then add the 8" to find the total linear inches, divide by 16 to get 3.5, then add 1 to that and round up to the nearest number resulting in 5 IsoJoists needed for the 4'8" long joist).
To properly frame when using IsoJoist you will need to space each joist 16" apart on center. Spacing the joists 24" on center or even further apart can cause issues with resonance and, in some situations, problems with basic stability. Within 6" of each end of the joist will require an IsoJoist attached for support and from there an IsoJoist every 16" in between each end.
Using IsoJoist is the most affordable way to create a floating floor. There are not currently any sound tests showing the effectiveness of our IsoJoist, but the concept is simple and recognized by most in the sound isolation industry as an efficient way to create a floating floor. To maximize effectiveness we recommend insulating any stud cavity created by using the IsoJoist to create a floating floor or a raised platform.
Installation of our IsoJoists is very straight forward. The IsoJoist installs in a friction fit style and requires no permanent fastening in any way. Your joists should be spaced 16" on center whether you use 2" x 4" or 2" x 6" studs as joists. Space each IsoJoist 16" on center along the length of the joist with an IsoJoist on each end of the joist. A standard 8 foot 2" x 4" joist would require 7 IsoJoists for proper, stable, installation. The installation drawing below shows a scenario where the floor is longer than a typical 8 foot stud. When this occurs it is still required to attach an IsoJoist at the end of each stud. Do not 'split' an IsoJoist between two joists.
Once you have attached the appropriate number of IsoJoists to your joists and laid out your joists on the floor you can now insulate the joist cavities. Standard fiberglass insulation that fits the depth of your joist cavities is recommended for all installations. Once you have insulated the joist cavity you can now finish the floor by nailing or screwing a layer of sub-floor to the joists.
For a dramatic increase in isolation add an additional layer of sub-floor with Green Glue in between layers or lay out our QuietGround underlayment over the top of the newly isolated floor. The picture below shows a typical installation for IsoJoists with the inclusion of Green Glue between two layers of sub-floor. The Green Glue is of course not as thick as pictured below.
| Composition: | EPDM rubber (ethylene propylene diene M-class rubber) |
| Product Consistency: | E2 Precision Cut |
| Shore A Durometer: | 70 +/- |
| Temperature Range: | -65F to 250F |
| Total Width: | 2" |
| Total Height: | 1 1/4" |
| Designed To Fit: | Any 2x lumber product |
| Coverage: | Approximately 1 piece per square foot |
~30 KB IsoJoist Product Specs
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