Something sticky..

July 7, 2009 9:34 AM

What specific product should I use to mount a 40 pound slab of slate to the wall?

I want to hang it like a picture, so shelves are out... I was picturing a vertical slide glued, epoxied or cemented to the back of it (sort of a long dovetail, with the flare facing the wall) and then a block of wood with that same dovetail routed out of it, that I would screw into the wall.

So, the slate with the dovetail would then slide down into the block that is secured to the wall. The part I'm not sure about is the glueing of the dovetail to the slate. The slate is not perfectly smooth on the back, though I would not consider it rough. It's slightly ripply.. Enough to make me concerned.

Which adhesive product would work best for this? I mean, if this thing falls off the wall, I'm gonna be in a heap of trouble :P Any glue experts out there?

posted by Glendale to home & garden (14 comments total)

For glue advice go here. If it were me I would consider trying velcro.
posted by snowjoe at 9:50 AM on July 7

Probably a construction adhesive such as PL or liquid nails, dispensed with a caulking gun. Allow plenty of time for it to dry (a few days, maybe), since it depends on evaporation to harden and that will take a while if the glue is sandwiched between 2 broad surfaces. Also, make that piece of wood large so there's a lot of surface area in play; this is not the place for delicacy.
posted by jon1270 at 9:54 AM on July 7 [1 favorite]

At 40 pounds I wouldn't trust glue for any length of time. I might try to paint a piece of angle iron to match and screw that into the wall as a minimal "shelf" and put brackets to hold it up.

At the museum I used to work at, metal brackets around the item was the way to go for things this heavy.
posted by advicepig at 9:55 AM on July 7 [1 favorite]

BTW, a straight dovetail is a pain in the butt to machine well; the tolerance between impossibly tight and sloppily loose is very small. A similar effect could be achieved with V-shaped parts, positive and negative, with interlocking dovetail-like angles on their edges. This would be easier to make, and self-tightening as you hung the thing on the wall.
posted by jon1270 at 10:03 AM on July 7

What kind of wall are you attaching to? I think that's going to be your limiting factor. Can you get to the back side of the wall, if it's 2x4s and drywall? in that case, you could mount through to a board set into the studs. Block? sleeve anchors. Brick or concrete? Wedge anchors. FOr peace of mind, put a couple in a line, then hang a wire over them. Even small wedge and sleeve anchors have pullout values of 1000 lb.

Now, the attachment to the slate. I'd epoxy a couple 2"x2" or larger plates, tap in some screws, and mount a wire across the screws. Easy to level, that way.
posted by notsnot at 10:15 AM on July 7

Seconding advicepig.

You definitely want to screw something into the stone, and have that catch on something screwed or nailed into the wall. Nothing else will hold indefinitely.
posted by Citrus at 10:16 AM on July 7

A French cleat screwed into studs will easily handle hundreds of pounds and is commonly used to mount kitchen cabinets. Construction adhesive (PL makes one specifically for granite and marble) to attach the slate to the cleat. You need to attach an equal thickness to the bottom of the slate to make it hang flat or better make a frame that goes all the way around. You can get away with material only 3/8ths of an inch thick if your wall is flat.
posted by Mitheral at 11:24 AM on July 7

Mitheral: "7A French cleat screwed into studs will easily handle hundreds of pounds and is commonly used to mount kitchen cabinets. Construction adhesive (PL makes one specifically for granite and marble) to attach the slate to the cleat. You need to attach an equal thickness to the bottom of the slate to make it hang flat or better make a frame that goes all the way around. You can get away with material only 3/8ths of an inch thick if your wall is flat."

Truth. Very good advice here.
posted by Gravitus at 11:27 AM on July 7

Thanks for all the response guys. Mitheral/Gravitus, that's great information.. Preciate it!
posted by Glendale at 11:53 AM on July 7

I don't have good luck with construction adhesives, perhaps due to application ineptitude or some such thing. It's probably not the adhesive's fault. That said, I'd probably use thinset, because I've done a fair amount of tiling. Cut a couple of cleats out of a matching thick slate tile and thinset the two together, then hang on the cleat you've put on the wall.
posted by RikiTikiTavi at 11:59 AM on July 7

The french cleat idea is a good one. Myself, I'd drill eyehooks into the stone and hang it from wires attached to a ceiling joist, like this system here.

Gluing it to the wall itself will never, ever work. I'd just drill bolts through the stone and into the studs before I'd glue anything.
posted by Cool Papa Bell at 11:59 AM on July 7

Just to be clear, the wall is 1" tongue and groove pine, so I'm not worried about having enough meat to grab on the wall side of things. My main concern is on the slate side. I was thinking PL/liquid nails, but wasn't sure that it would support 40 pounds.

Ceiling joists aren't an option. The slate needs to look as if it is hovering against the wall, with no visible support (just like a picture).

Thanks again for all the response!
posted by Glendale at 12:32 PM on July 7

I would look into the same type of technology thats used to keep flat screens and plasmas up on the wall. Not only do they hold the same amount of weight...but they keep up FLAT things.
posted by hal_c_on at 12:51 PM on July 7

Well, flat screens have nicely machined boltholes in the back as your mounting points, so you can't really compare. If the slate is thick enough, you might be able to set bolts & anchors in the back of it. If it's too thin for that, I'd look into two-part epoxies. Your local hardware store probably has a demonstration piece where they've glued all kinds of crazy crap to a glass bottle. The epoxy is very thick and looks terrible, but that part would be facing the wall anyway.

The french cleat is a fine way to hang things. Make sure you put some kind of cap on the end so it doesn't slide off the side.
posted by echo target at 1:19 PM on July 7