Adding Low Voltage Box - Found Plywood Behind Drywall


Old 12-20-17, 08:12 AM
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Adding Low Voltage Box - Found Plywood Behind Drywall

This may not be the correct forum, but I wanted to see if anyone could help. Even though it's related to data lines, I thought maybe the electrical forum would have better insight. I bought a small office condo, and I have been running ethernet cable throughout. I went to make a drop yesterday, and I couldn't cut through the sheetrock. I removed the existing telephone jack, and I realized that there is plywood behind the drywall. Has anyone encountered this before? My initial thought is that it is some type of fireproofing measure, but I don't know for sure. It appears to only be on the common walls. I have no idea if I'm allowed to cut a hole in the plywood, or if I'd be better off using some type of surface mount box.
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Old 12-20-17, 08:50 AM
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Look at other receptacles on that wall and see if they were cut into the plywood. My guess would be they are cut in.
I can't give you a definite answer, but plywood on walls is usually for shear value not fire proofing.
In California, shear walls are common in new homes (on certain walls). The plywood is usually 3/8" Structural I grade.
Old 12-20-17, 08:51 AM
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Do you mean the common walls between your unit and another tenant in the building? It could be a shear wall if the wall is structural, which would be OK to cut for a box. Plywood isn't usually used for firestopping - that would be double thick type X drywall or masonry. I'm thinking it's maybe just a security measure to prevent you from easily breaking into the neighbor's unit using a utility knife.
Old 12-20-17, 09:25 AM
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Yes, it appears to only be on walls that are shared with another tenant. The other walls have nothing behind them. What is the best way to cut it?
Old 12-20-17, 09:29 AM
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A Rotozip or oscillating tool would work.
Old 12-20-17, 10:06 AM
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Read your condominium documents and contact the trustees or management company to find out if you may run additional wiring of your own in (or cutting holes to access) the common space that makes up the stud cavities between your unit and the next.

Low voltage wiring needs to have appropriate flammability rating but does not have the general requirement of being multi-conductor cable or being run inside a conduit or having an equipment grounding conductor.
Old 12-20-17, 04:35 PM
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Heed well what AllanJ has written. Know also that some jurisdictions have special requirements for low-voltage and/or data cabling that might require an electrician with a special "low voltage" license to do the work in a multi-tenant building.
Old 12-20-17, 07:31 PM
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I'd use a jigsaw to cut through the drywall and plywood together.

The other option would be to use a surface mount box and run the cables down the exterior of the wall in wiremold.

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