Framing a heavy mirror

[Starboard]

Hi, Framers,


Thanks to friendly advice on this forum, my first framing efforts (a large tray frame for a canvas) were really rewarding.

So I am now commissioned by my best, most demanding and only customer (my wife) to make a quite large-ish mirror: glass size would be 1,000 x 1,000mm.

Quick look up on the net gives average weight for MDF 4mm backing at 3kg/sqm and glass at 10kg /sqm for 4mm thick mirror, unsurprisingly 15kg/sqm for 6mm.

Depending on backing/mirror thickness, this would be between 13 and 20kg excluding moulding.

So, there is a deluge of questions such as:

* What is, in your experience, the best building method? I was thinking of glueing the mirror to a backing (MDF or other) for safety, and also using the backing for fixing in order not to stress the frame, but that may no be the best option.
* Would you go for 4 or 6mm? My guess is, 4mm + glued to backing is probably enough, this is nit a commercial application
* What material / thickness would be good for the backing?
* Do you leave some wiggle room between the mirror and backing and the frame ? Are there any expansion issues to take into account?
* What type of fixings would you recommend?

I found this type of system from a commercial supplier, but I am not sure about the D ring fixings on the frame

Thanks for any pointers. I could always "give it a go", but usually, I end up finding there was one or several "tried and tested ways" of doing things. Ask people who know!

[pramsay13]

I think you are maybe overthinking things.
At that size I would be happy with 2mm mirror and backing.
It would probably be easier just making it 4' x 3' which is the standard sheet size, otherwise you will have to order an oversized sheet and then cut down to size. If it has to be square make it 915mm x 915mm.
Then just frame as normal and add a wire and hang on hooks. If you're worried about the weight you could use cleats.

[JKX]

I don’t think you can buy 2mm mirror glass - certainly not from Wessex or Centrado anyway; they start at 3mm and it’s already safety-backed. The safety backing is only a polypropylene film but maybe that and the silvering makes it 3mm minimum?

So no need to stick mirror to backing - if it does break that’s two things to replace!

2mm glass for a mounted thing that size is OK - even if borderline, but in that case there would be an air gap between glass and artwork/backings. So 3mm against a backing would be fine.

I’ve had plenty of mirrors in for repair and have seen a lot of overkill, like being stuck in to the rebate with mastic, then the backing board being held in with quadrant moulding nailed and glued to the rebate, huge screw rings and wire like a coat hanger, etc.

Here’s one I used to have, solid oak frame and backing - held in with turn buttons, albeit pretty heavy duty ones.

I would just use framers points and foil tape. I’d make sure the rebate was filled to put the backing as close to the wall as possible though. If weight is an issue use correx. Two pieces bonded together with the flutes going perpendicular makes for a very strong but lightweight board.

Mirrors are best flush to the wall, so maybe not wire. Z bars are good and could go top and bottom, then there are strap hangers etc - mine as you can see used keyhole hangers which were fine but take very accurate positioning of wall fixings.

I

[Starboard]

Thanks for the pointers – and also apologies for the long delay in this reply, I forgot to click the "Notify me when a reply is posted" button.

So, no glueing the mirror to the back board, a good few points will secure the whole lot.

Here it is, 8 kg in total as the frame is heavy and minimum mirror thickness i could get was 4mm.

I like the idea of the Z hangers, but at 8kg, I think that a 3hole strap ring should be just fine. As the frame is wide, I can probably position the strap at an angle, more or less in line with the cable direction. Will check your suggestions for other types of hangers.

Thanks for your help.

[NTG999]

I use quite a lot of these
https://www.lionpic.co.uk/p/42533/Ancho ... es-pack-50
Frame looks great

[Justintime]

I use these heavy duty hangers a lot
https://www.lionpic.co.uk/p/10574/3-Hol ... pack-of-50

[Starboard]

Hi Justin,


Got these ones – except not the gold plated ones.

The frame is fairly wide. Would you see any advantage in positioning the strips sideways so they are (more or less) aligned with the traction from the hanging cable?

Thanks

[Starboard]

I use quite a lot of these
https://www.lionpic.co.uk/p/42533/Ancho ... es-pack-50
Frame looks great

Thanks. I am going towards this simpler solution now.

[JKX]

Mirrors are best not hung with cord/wire (or whatever a “cable” is!) due to it tipping forward.

If you must use that then please use TWO wall hooks, with the angles between them and the frame hangers at sixty degrees.

This should apply to most frames

Here’s why

[Justintime]

Imo opinión every Framer should have that diagram printed out and kept somewhere handy as a reminder and to educate customers who are hanging heavy pieces.
FYI those heavy duty hangers I linked are used vertically with wall hooks rather than with cord.

[Starboard]

I have done just this... May even possibly frame it!

The idea of simply putting two wall hooks (I slap myself for not even thinking of it) is of course a much better solution to reduce the lateral force

Excellent ressource, and I like the simple "rule of thumb" calc.

As a beginner, I really appreciate being able to tap into the knowledge of "those who know".

Cheers

[Justintime]

Sorry I've only just noticed that your original post showed exactly those hangers.

[prospero]

Sometimes you have to abandon conventional thought when it comes to weighty frames.

I came up with this concept many years ago for mirrors....

Make a sturdy subframe the size of the mirror. You can engineer a cleat system into the subframe and attach a
batten to the wall with as many fixings as necessary. This way the outer frame serves only to keep the subframe
and mirror together. I have a full sheet (4x3') mirror on my bathroom wall with a ½" wide beech moulding around it.
It's solid as a rock and is perpendicular to the wall.

I found t&g pine cladding the most economical option. Rip the 'tongue side off and you have a 100mm x 8mm plank.
If you use two layers you can form half-lap joints and add cross braces with no fancy woodwork methods, just 90º cuts
and a bit of gluing and screwing. The resultant frame is very strong but fairly lightweight.

bigmap004.jpg (18.05 KiB) Viewed 41277 times

[Starboard]

Sometimes you have to abandon conventional thought when it comes to weighty frames.

I came up with this concept many years ago for mirrors....

Cor, this looks sturdy indeed. Sounds like an excellent option for the big mirrors. Thanks for showing me this layout

[prospero]

That one was close to 6ft square. Not for a mirror but a big map. It did get quite a hefty frame on it but
it could have had a very narrow frame and still have been solid as a rock.

The weak link with hanging heavy frames is usually the wall attachments. I like big hammer fixings when going
into brick. But the thing with cleat fixings is you can wack in as many fixings as you like and the weight is distributed
along the length of the wall batten.