Backing for Mirror

[Keith Nuttle]

We are planning on putting a mirror to cover the TV hole above our fireplace. The plan is to remove minimal trim, place shims on the sides of the existing opening so the mirror is flush with the back edge of the mantel and the existing trim.

I plan on cutting this backing board so it would fit into the opening, and holding it in with quarter round or similar.

What would be best for this backing board. MDF, plywood, etc.

Should the mirror be bonded to the backer board. If so how?

I plan to remove the electrical plug, put wire nuts on each wire and wrap the ends in tape. I am going to do nothing with the phone and cable jacks that are there.

Any comments.

Thanks.

[-MIKE-]

A structural backer is a good idea just to prevent to possibility of a person or part of a person going through it. Bonding with mirror adhesive or contact cement is also a good idea to prevent glass from falling all over the place if the mirror were to be broken in any way.

[dadiOH]

Whatever as long as it is reasonably rigid. I used to have a condo with 12' of floor to ceiling mirrors on the wall (which was drywall).

I would use the black goop that mirror people use for that purpose. Actually, I imagine most any would work...silicone, acrylic, Liquid Nails, linoleum paste, etc. Just assure that it is something that won't damage the silvering.

[Keith Nuttle]

My concern is the length of the hole. I planned to put in the backer board only, with no studs in the 41" length. The plan is to make it removal IF there is ever a need to access the area behind it.

My thinking is at minimum a 3/8 piece of plywood but am unsure if that is adequate.'

Thank to all who have responded so far. It looks like my wife is going to get her wish, to have it in for a family get together in mid December.

I know but I am slow and like to thoroughly think things through.

[-MIKE-]

At 41inches, 3/4" mdf or 7 or more ply plywood would be plenty stiff enough. You're right about the 3/8, too flimsy, although it would accomplish the goal hold holding mirror together if something were to run into it... and you could always screw some sort of frame to back of it.

But 3/4 mdf is pretty cheap and so is non-sanded 3/4 plywood.

[-MIKE-]

Mike, have you not found that the wire nuts hold on to metal better than the insulation? At least in my experience, when I've left even just an eighth or quarter inch of wire for the nut to grab, it's held much better than when grabbing just the insulation.

The only reason I know this is having recently put temporary wire nuts on romex for our remodel. The ones that were on insulation only almost fell off with an untwist or two. The ones on bare wire had to be untwisted at least a couple full turns before they could be pulled off.

[clare]

The only problem with gluing the mirror to the backboard is the very REAL possibility that the glue will pull the silvering off the back of the mirror. How are you intending to mount the mirror? Is it in a frame, or will you use mirror brackets?

[clare]

3/8 or 1/2 ply would be plenty, even over 41 inches of width if it is supported top and bottom a well as both sides - it's only, wat - 32 inches high??

[Sonny]

Put some temporary studs behind your ply board, if your concern about stabi= lity still exists. At minimum, just wedging them (top or bottom) snuggly/= tightly in place should work fine, for preventing someone from accidently p= ushing the mirror back into the recess, if that is the concern.

Sonny

[-MIKE-]

Not a problem...

[Larry Jaques]

Thick ply. Hinge it on one side, fireproof it, and make a secret storage area behind the mirror.

How about screwing the mirror to it from the back through the ply to the mirror frame?

Ssh! Don't tell anyone about the secret storage space. ;)

-- They must find it difficult, those who have taken authority as truth, rather than truth as authority. -- Gerald Massey, Egyptologist

[Keith Nuttle]

The plan is to put it on the backer board with the "glue" that I plan to buy from the same company that I am buying the mirror.

I am buying the mirror to be a quarter of an inch shorter than the actual width of the opening. The backer board will be the same size as the mirror.

There is a quarter inch lip at the mantel. As I said earlier I will put shims on the exiting casing so the mirror is the width of the quarter round from the front of the casing. I will then hold the whole thing against the shims with quarter round or similar molding. The depth from the front of the casing will be a determine on esthetics.

[Leon]

Plywood would be the most resistant to something penetrating.

Not necessarily, I would not, see below.

What ever you do be very careful in choosing your bonding agent. Many adhesives and IIRC silicone base adhesives will quickly deteriorate the mirror reflective material. Go to your local glass store and ask what to use.

[Leon]

NO! Actually many adhesives will react with the mirror coating. You want the correct adhesive.

[Jim Weisgram]

Those abandoned electric wires would still be connected, so the hot wire remains hot? I believe that's a potential future fire hazard, wire nuts and electrical tape or not. I am thinking rodents and teeth when I say that.

I suspect code would require a junction box with a cover that provides access to the wire ends, but I am not an electrician and I haven't bothered to check the code.

[-MIKE-]

How is that different from any other romex running through the walls?

That is probably true.

[Dave]

On Wed, 24 Oct 2012 23:19:39 -0500, -MIKE-

And, with my limited understanding of electrical code, I believe there also needs to be easy access to that junction box. I'm not exactly sure what makes up easy access.

[Leon]

Is the electrical outlet in the way? If not why do anything at all with it? What makes covering it up any different than putting a sofa in front of a wall plug?

[Keith Nuttle]

As I said it is above the fireplace, too high to have to bend over. ;-)

As I remember there was a big discussion on this group(?) about closing in plugs a few months ago, and I was just checking if there had been any changes. As I understood from a practical point of view there was no problem, but there may be a problem with local regulations.

[-MIKE-]

A Sawzall? :-)