Plywood backerboard for panel

[Davidwms]

I'm rewiring my parent's house. They need a new panel I have built a small wall to support the new panel in their basement. I plan on mounting plywood on this wall. Are there any specific requirements for the plywood that prohibited me from mounting the panel directly to the plywood?

 

[infinity]

Most guys just slap the plywood on the wall. We always mount 4 plywood strips on the wall first and then attach the plywood to that. We also always paint it black.

 

[Jpflex]

Most guys just slap the plywood on the wall. We always mount 4 plywood strips on the wall first and then attach the plywood to that. We also always paint it black.

Dont most use flush mount panels type pannels and install between studs. or if surface mounted, install metal struts horizontally between wall studs and mount the panel to these?

 

[infinity]

Dont most use flush mount panels type pannels and install between studs. or if surface mounted, install metal struts horizontally between wall studs and mount the panel to these?

Around here many panels go in the basement which is unfinished. That translates to it being slapped on a piece of plywood on the foundation wall.

 

[Jaybone812]

I personally sister the wall with 2x4 studs and secure them to the ceiling joist if possible of use a Ramset or tapcons to secure the 2x4’s to the foundation, then aecure the ply wood backer to the studs , and mount the panel on the plywood backer, but the nec does not require us to mount the backer a certain way as long as the panel can secures to the backer

 

[kwired]

I personally sister the wall with 2x4 studs and secure them to the ceiling joist if possible of use a Ramset or tapcons to secure the 2x4’s to the foundation, then aecure the ply wood backer to the studs , and mount the panel on the plywood backer, but the nec does not require us to mount the backer a certain way as long as the panel can secures to the backer

NEC doesn't require a backer. If the surface you wish to use is not suitable to mount to then I will make something more suitable. This usually something for old structures. I've almost always mounted right to the wall in newer structures. They generally build them with intention to be dry at least around here they do. Moisture just causes problems for about anything imaginable.

Many say damp basement, damp walls why would you mount the panel to them? That is a good point, but if this is that kind of an environment then it isn't a great place for the panelboard either, especially the typical "load center", maybe a commercial panel in appropriate cabinet might be ok.

 

[solarken]

I'm rewiring my parent's house. They need a new panel I have built a small wall to support the new panel in their basement. I plan on mounting plywood on this wall. Are there any specific requirements for the plywood that prohibited me from mounting the panel directly to the plywood?

No NEC requirements , but you may want to look at any local code requirements. I always apply a decent quality primer/paint to both sides and the edges, for at least some protection and aesthetics.

 

[Jaybone812]

NEC doesn't require a backer. If the surface you wish to use is not suitable to mount to then I will make something more suitable. This usually something for old structures. I've almost always mounted right to the wall in newer structures. They generally build them with intention to be dry at least around here they do. Moisture just causes problems for about anything imaginable.

Many say damp basement, damp walls why would you mount the panel to them? That is a good point, but if this is that kind of an environment then it isn't a great place for the panelboard either, especially the typical "load center", maybe a commercial panel in appropriate cabinet might be ok.

I’m aware we aren’t required to use a backer and I never said we are . I simply described my preferred method when using one. He asked if they had specific requirements when using a backer so I answered the question . Which is no if we choose to use a backer the nec does not have rules as to how it must be mounted . If he had asked if using one is required by the nec I would have answered that question , saying no they don’t . lol


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[ModbusMan]

Plywood sheet (with or without spacing/furring strips behind) is also the way of things in NE Ohio basements, though rarely do I see them painted as infinity does. Just make sure the can has a dimple for the MBJ, or that you put it in before mounting, assuming one's required.

 

[kwired]

I’m aware we aren’t required to use a backer . He asked if they had specific requirements when using a backer to I answered the question . Which is no if we choose to use a backer the nec does not have rules as to how it must be mounted . If he had asked it using one is required I would have answered that question saying no they don’t . lol


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One potential convenience of a backer when the wiring methods are primarily NM cables is if it is oversized enough you have something to secure cables to.

I hate side entries to load centers, especially NM cable entries and try to avoid that so only place I make arrangements for fastening cables is usually above and/or below the load center. Mounting a load center on basement wall and a wood strip about the width of the cabinet about a foot above the load center is pretty common for my installs. I've seldom needed more than what Square D has for KO's in top/bottom of their load centers for 40 circuit or less models. If you are mounting between studs sides are a pain to enter anyway.

 

[Jaybone812]

One potential convenience of a backer when the wiring methods are primarily NM cables is if it is oversized enough you have something to secure cables to.

I hate side entries to load centers, especially NM cable entries and try to avoid that so only place I make arrangements for fastening cables is usually above and/or below the load center. Mounting a load center on basement wall and a wood strip about the width of the cabinet about a foot above the load center is pretty common for my installs. I've seldom needed more than what Square D has for KO's in top/bottom of their load centers for 40 circuit or less models. If you are mounting between studs sides are a pain to enter anyway.

I’m in agreement with pretty much every thing you said. 3 years ago my job description primarily was to was working foreman of crews that wired mixed use multi family resi with lower level retail space . And obviously in those applications, the dwelling units were wired in nm cable so I was installing and cutting in load centers on daily basis and if even I was able to enter enter the enclosure using the side ko’s on new roughs I refused to do it . Top or bottom I felt was the cleanest easiest entry
Nowadays I’m hardly if ever on new residential projects , my work is mostly on the commercial side , and at least 2-3 installs of hardwired evse per week sometimes more , because we are tesla certified installers . So now a days when landing the evse circuits in existing panels , mostly located in unfinshed basements, I enter the enclosure through the side knockouts for more than half of the units I wire. Not out of preference but because it’s quickest, easiest entry with the path of least resistance when entering existing panels especially when there’s been multiple different pairs of hands in that panel
But if I’m on a resi remodel or addition which includes adding one or more basement panel locations which does happen periodically my go to method is what I explained , sistering the wall with studs by securing them to the ceiling joists then attaching my panel backer to the studs , securing the panel to that backer. And still only enter through the top or bottom kos in new panels . I don’t use 2x4 or furring to secure my cables before entering the enclosure i usually use tsgb16’s Secured between the studs I drop from the ceiling joists just above the ply wood backer and secure the cable with cable ties

 

[Eddie702]

No requirement for plywood but it is helpful to have something to attach the nm cable staples to and I think it is a better job.

Also, concrete or block may contain some moisture so having it on plywood is a good idea.

I have heard that some inspectors have asked for "fire retardant plywood" but I never had issues with that and don't even know if it exists.

Could be a Massachusetts thing. Wouldn't be surprised.

 

[ModbusMan]

I have heard that some inspectors have asked for "fire retardant plywood" but I never had issues with that and don't even know if it exists.

It's a real thing... has a sort of reddish tinge to it. Couple years back while doing an office remodel, our AHJ asked that we put that up between a conference room and a loading dock rather than the fiberglass batt and drywall the GC originally planned on.

 

[Jaybone812]

No requirement for plywood but it is helpful to have something to attach the nm cable staples to and I think it is a better job.

Also, concrete or block may contain some moisture so having it on plywood is a good idea.

I have heard that some inspectors have asked for "fire retardant plywood" but I never had issues with that and don't even know if it exists.

Could be a Massachusetts thing. Wouldn't be surprised.

I’m also located in mass , and have never heard of any mass electrical inspector asking for a fire retardant backer because it’s a backer board for electrical equipment , I’ve only seen that required if you installed the backer in a location that required the 2 hour fire rating , for instance , you install a backer board on a wall in a multi family dwelling mechanical room , and that wall is a shared space or demising wall between common space and a dwelling unit. And even then if the existing wall meets the 2 hour rating there’s no reason for the plywood to carry the same two hour rating


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[Jaybone812]

It's a real thing... has a sort of reddish tinge to it. Couple years back while doing an office remodel, our AHJ asked that we put that up between a conference room and a loading dock rather than the fiberglass batt and drywall the GC originally planned on.

I’m aware it’s a real thing and I try to have it installed as a backer for my equipment located in commercial electrical rooms . But that’s because that location requires the backer to have a 2 hour rating

 

[garbo]

Depends if wall is in a damp ( like basements of old houses ) or if dry. Damp location would install 2 by 4's to wall then mount painted 3/4" exterior plywood on 2 by 4's. I mounted my panel on 3/4" exterior plywood directly to poured dry concrete wall that I placed two coats of glossy Rustolium green paint on 45 years ago. Paint still glossy and wood is in great shape. Too many people cut corners on the paint. Always cover entire front, back & sides. Back in the 1960's when they were still allowing Ultility meters to be mounted inside of small row house garages the local utility company had a rule in thier blue book that required thier meters in garages be mounted on plywood.

 

[kwired]

Depends if wall is in a damp ( like basements of old houses ) or if dry. Damp location would install 2 by 4's to wall then mount painted 3/4" exterior plywood on 2 by 4's. I mounted my panel on 3/4" exterior plywood directly to poured dry concrete wall that I placed two coats of glossy Rustolium green paint on 45 years ago. Paint still glossy and wood is in great shape. Too many people cut corners on the paint. Always cover entire front, back & sides. Back in the 1960's when they were still allowing Ultility meters to be mounted inside of small row house garages the local utility company had a rule in thier blue book that required thier meters in garages be mounted on plywood.

Damp causes mold and air quality issues. Kind of doesn't really matter if you put wood between the wall and your panel, the whole basement is likely still going to have damp issues, if anything you gave your panel a couple extra years by not fastening directly to the wall. Anyone that doesn't want to remedy the damp problem probably isn't all that concerned about how good the electrical system is anyway. Many old houses that are worth it around where I am have had contractors come in to such basements and remedy the moisture problems and their indoor air quality has greatly improved because of it.

 

[infinity]

It's very rare that a basement is actually a damp location except maybe in a very old building. If a modern home has a basement that meets the definition of a damp location then you have bigger problems than just mounting plywood to the wall.

If you're going to call a basement a damp location then you cannot run NM cable in it, you would need damp location covers on all of the switches and receptacles, light fixtures would need to be listed for damp locations, etc.

 

[kwired]

It's very rare that a basement is actually a damp location except maybe in a very old building. If a modern home has a basement that meets the definition of a damp location then you have bigger problems than just mounting plywood to the wall.

If you're going to call a basement a damp location then you cannot run NM cable in it, you would need damp location covers on all of the switches and receptacles, light fixtures would need to be listed for damp locations, etc.

True, the damp many often are thinking of in basements isn't normally what NEC would call damp, but is enough to cause indoor air quality problems and possibly mild corrosion issues at times.

 

[garbo]

Damp causes mold and air quality issues. Kind of doesn't really matter if you put wood between the wall and your panel, the whole basement is likely still going to have damp issues, if anything you gave your panel a couple extra years by not fastening directly to the wall. Anyone that doesn't want to remedy the damp problem probably isn't all that concerned about how good the electrical system is anyway. Many old houses that are worth it around where I am have had contractors come in to such basements and remedy the moisture problems and their indoor air quality has greatly improved because of it.

There is a big difference in on old house that has a damp cellar with old stone walls & cracked floors and no windows,ventilation or heat compared to homes built with basements ( which are only partially below grade level ) poured concrete or cement block walls, windows and if forced hot air heat have air registers that keeps humidity level stable entire year.