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How to attach floating mantel with corbels?

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Forum topic by JocknJill posted 12-05-2015 05:31 AM 1346 views 0 times favorited 16 replies Add to Favorites Watch
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JocknJill

4 posts in 372 days


12-05-2015 05:31 AM

Topic tags/keywords: mantel toggle bolt floating shelf question

I’m looking for a way to attach a floating mantle with corbels (essentially a floating shelf, pictured below) to portions of a hollow plaster wall just above the brick fireplace surround (also pictured below). I want it to be super solid to be able to display large rock fossils on it (I love rocks).

I thought I would put toggle bolts through each corbel into the wall and at a few places along the mantel shelf either on the top or bottom (pocket hole style), but messing with a few test pieces in my shop (pictured below) showed that if I countersink the head of each bolt and the bolt head slips into the countersunk hole with the “butterfly” toggle behind the wall already, I could be pretty screwed. The toggle bolt would spin but gain no traction, and I’d be stuck with a mantle hanging off my wall. (...Although maybe I could use that downward cantilever force to make the toggle grip the back of the wall. I just tried this on a test piece, and it seems to work. But I’d have to insert all the toggle bolts at once, and tighten each bolt a tiny bit at a time so that none of them lose traction.)

Another problem is that the toggle bolts require 3 different drill hole sizes—1/8” for the bolt shank, 3/8” to sink the bolt head to later be puttied, and 1/2” to push the toggle through the wall. I couldn’t mount the bolts one at a time since I’d have to tighten down one first to be able to mark and drill the holes for each next bolt placement, so it would be impossible to drill the 1/2” hole in the wall behind the 1/8” hole for the bolt shank. (Maybe i should make a template from a scrap board for the drill holes?) Another problem would be the fact that the toggle would have to be placed behind the corbel after the bolt shank is pushed through the hole, which would be impossible if the mantle were already snugly fit against the wall by 1 or 2 bolts already.

I’ve considered adding a backing board to the piece, in which case I would screw the corbels and mantle shelf to the 3/4”x7.5’ pine board and easily mount the backing board to the wall with toggle bolts. I may still have problems with the bolt spinning and not gripping the toggle against the wall, unless, like I said above, I pulled the board away from the wall to get the toggles to grip behind the wall.

This whole plan just seems unnecessarily complex. Any other ideas out there that would put me out of my misery? My girlfriend would be happy, too, because then she’d be able to hang the stockings before Christmas. Thanks for your help in advance!



16 replies so far

View MrUnix's profile

MrUnix

4247 posts in 1667 days


#1 posted 12-05-2015 06:41 AM

I absolutely hate those wing toggle things and refuse to use them! Not only are they a PITA to install (as you have already figured out), but you can’t remove the screw once installed should you ever need to. For something like you are doing, I usually try to hit at least two studs – more if possible. But another alternative would be to use those plastic E-Z twist lock anchors, which work great and have some pretty good holding power. If you could hit a couple studs, and then use those on the other mount points, you should have enough holding power. Maybe someone else will have a better solution and chime in.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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JocknJill

4 posts in 372 days


#2 posted 12-05-2015 06:51 AM

Brad, thanks for the idea…I have some of those, but I’m not sure if they’ll hold in plaster and if they’ll accept other screws like 3” deck screws (I would have to drill through 2” of the corbel to get to the wall.) I’ll inspect the wall better and read about whether these can be used in plaster.

About studs: I can’t get a reliable reading from my stud finder along the entire length of wall that I’m mounting to, which is why I think it’s plaster. Also, the wall is wavy, so another reason to think it’s plaster.

Still more thinking to do…

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MrUnix

4247 posts in 1667 days


#3 posted 12-05-2015 07:00 AM

Yeah… lath and plaster might make it a bit more challenging :) Those anchors would probably work if you have rock lath, but might not for wood or metal lath – although I really don’t know for sure. I’d still try to find the studs and use as many as possible… some test holes where the mantle will eventually be could find you one, and you could measure out the rest. At any rate, good luck on it!

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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Tennessee

2410 posts in 1982 days


#4 posted 12-05-2015 01:08 PM

There may not be any studs up there because there is a chimney behind that plaster. You may drill into that to find that you have brick or a metal insert just behind the plaster, and they just put up the plaster wall to make a surround around the brick fireplace. The outlets would be attached to what could be the first studs holding the insert, or the beginning of an actual wall.

That is why your stud finder is not working, and if it is plaster and lath, that could also be why.
Also, I used to own a very old home where they simply put up plaster right over the brick chimney. Explains the waviness.

But a very small drill hole would tell soon enough if there is brick or metal back there.

If there is only plaster, they make a zinc plated metal version of that anchor that Brad showed.
Supposed to hold up to 50 lbs each in plaster.

-- Paul, Tennessee, http://www.tsunamiguitars.com

View dhazelton's profile

dhazelton

2326 posts in 1764 days


#5 posted 12-05-2015 02:10 PM

Gotta know more about how the wall is constructed – is it plaster over a brick chimney? Is that a woodstove with a 6 inch pipe going up or a gas stove direct vented with conventional framing above it? That looks like a modern home and I would assume there are studs in there. Any plastic mollys you put in plaster won’t hold well. If you’re going to put some weight on it I’d figure out how to get lag screws securely into that wall. You also have wiring in there, assuming it’s not BX so you have to be careful as the wire could drop down to one box then go horizontally over to the other one.

Have you considered making a full surround that rests in the floor? It would be a lot simpler to anchor something like that as the floor really supports the weight of whatever you put on it.

View a1Jim's profile

a1Jim

115207 posts in 3045 days


#6 posted 12-05-2015 03:26 PM

The way I almost always hang mantles is to build the mantel like a box but leave the back part of the box off,then I connect the back of the box to the wall with long screws or lags into studs and then slide the box on to the back section with finish nails,or hang it with a french cleat .

-- http://artisticwoodstudio.com Custom furniture

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waho6o9

7180 posts in 2045 days


#7 posted 12-05-2015 03:43 PM

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waho6o9

7180 posts in 2045 days


#8 posted 12-05-2015 03:52 PM

View clin's profile

clin

514 posts in 464 days


#9 posted 12-05-2015 10:33 PM

I’d go with a1Jim’s cleat idea. That’s how I have done this. Maybe hog out the back of the corbels and attach individual cleats that mate with each one. Of course you still have to be able to attache those cleats to something relatively solid. But at least you can do that without regard to how it looks since it will get covered.

The photos seem to distort the size of the mantle, so I can’t tell how thick the “shelf” is. If it is thick enough, you could perhaps hollow out the back edge of that to accept a narrow cleat that runs the length of it. Then you can at least anchor that cleat anywhere you want.

Backing board idea is good as well. But screw to studs. There has to be some framing in that wall. And easy enough to patch over the screws to hide them.

-- Clin

View builtinbkyn's profile

builtinbkyn

651 posts in 408 days


#10 posted 12-05-2015 10:53 PM

I do it the way Jim does, but since you’re at the stage you are, these Hilti anchors should do. If you miss, you cut off the plastic, let the wing fall into the wall and try again.

Edit: Are you sure the sheetrock isn’t laminated to the masonry? That would preclude a toggle and require a different anchoring system.

-- Bill, Yo!......in Brooklyn :)

View JocknJill's profile

JocknJill

4 posts in 372 days


#11 posted 12-06-2015 04:02 AM

dhazelton: It’s a wood stove with a 6” pipe going up the existing chimney. House built in 1954 but renovated in 2008. That wall is the only remaining plaster wall, with cracks and all.

MrUnix and Tenessee: I will try some test holes and will try to locate some studs, which would solve my problem.

a1Jim: Cleat is pretty much a moot point—I am stuck with a butt joint along the back of the piece since I don’t have the tools to hollow out a space for a cleat. I don’t have a router and am not sure how I would do it otherwise, unless there is a way with chisels, circ saw, recip saw—those are what I have.

dhazelton, a1Jim: there are only about 8” between the edge of the brick and the bookshelves, and clearance is required for our wood stove, so putting a wooden “legs” that the shelf rests on would be awkward with the narrow space. The mantel shelf is 1.5” thick and 6.25” deep by 71” long. The corbels are 3”x6”. The shelf is composed of 2 1×6s sandwiched together with a 1×2 on the face.

Next step will have to wait til next week! Don’t you hate having to put down a puzzler?

View Hammerthumb's profile

Hammerthumb

2533 posts in 1443 days


#12 posted 12-07-2015 11:07 PM



The way I almost always hang mantles is to build the mantel like a box but leave the back part of the box off,then I connect the back of the box to the wall with long screws or lags into studs and then slide the box on to the back section with finish nails,or hang it with a french cleat .

You musta been a few years younger in that picture Jim!

- a1Jim


-- Paul, Las Vegas

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a1Jim

115207 posts in 3045 days


#13 posted 12-07-2015 11:12 PM

Ha Ha
That’s not me Paul,just a photo I got offline to use as an example.

-- http://artisticwoodstudio.com Custom furniture

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chrisstef

15678 posts in 2474 days


#14 posted 12-07-2015 11:54 PM

Can you pull the faceplate off of those outlets and see what the box is attached to? If you can find 2 studs, as i suspect you may find next to those boxes, it may help locating others. Id go over 16 then 24 and check. Or measure the distance between two studs and guesstimate that they previously spaced studs evenly. Plaster may equal true dimension studs as well.

All else fails, theres gotta be a local jock that would help out.

Lol paul. A few??

-- rock, chalk, jayhawk

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JocknJill

4 posts in 372 days


#15 posted 12-08-2015 03:25 AM

Chrisstef, thanks for the suggestion—that will be my next step. What do you mean when you say that “plaster may equal true dimension studs?”

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