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Screwing fireplace mantle brackets into slate rock


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So I've got a nice little job for the new forge. Three fireplace mantle brackets. However, I am a little concerned about proper attachment.

I saw some mantle brackets done by a somewhat well known smith 2 hours north of me, and quite frankly I could have yanked them out of the wall with a light jerk. I'd rather mine not be like that.

So here is what I have: three brackets with 2 or 3 screws each being screwed into a 3 inch thick base of real creek stone, mortar, and cement board. I can't screw into the studs behind this base because they are not evenly spaced. I also cannot just pre-drill and screw directly into the stone because this type of rock will chip and crack almost certainly. (doesn't make for good word-of-mouth advertising!)

I am going to do some blackened square head lag bolts....at least that's my plan. Question is, how do I attach it to the rock? Can I get some gigantic (I'm thinking 1/4x2 or 3" lags) anchors like you use in sheetrock? Or is there something else?
Whatever you would use, where do you get it?

Thanks for your help in advance!

Thoughts???

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So I've got a nice little job for the new forge. Three fireplace mantle brackets. However, I am a little concerned about proper attachment.

I saw some mantle brackets done by a somewhat well known smith 2 hours north of me, and quite frankly I could have yanked them out of the wall with a light jerk. I'd rather mine not be like that.

So here is what I have: three brackets with 2 or 3 screws each being screwed into a 3 inch thick base of real creek stone, mortar, and cement board. I can't screw into the studs behind this base because they are not evenly spaced. I also cannot just pre-drill and screw directly into the stone because this type of rock will chip and crack almost certainly. (doesn't make for good word-of-mouth advertising!)

I am going to do some blackened square head lag bolts....at least that's my plan. Question is, how do I attach it to the rock? Can I get some gigantic (I'm thinking 1/4x2 or 3" lags) anchors like you use in sheetrock? Or is there something else?
Whatever you would use, where do you get it?

Thanks for your help in advance!

Thoughts???


If I understand your installation correctly. You might try an anchor called a moly bolt. It goes in to the wall and expands behind the wall as you tighten it. You are not limited to the bolt that comes with it. I have used them in simular situations and exchanged the machine bolt that come with it a pan head machine bolt for a flat head machine bolt. Then counter sink your part for the flat head machine bolt. After it is installed I would have made rosettes to be siliconed over the top of the screw head to cover it.
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What is important is how heavy and what is the overhang of the mantle over the brackets, not mounting the brackets themselves. If nothing was placed on top of the brackets, then it would not matter how you mounted them. So you are mainly dealing with a shearing force if the mantle is not overhanging the brackets too much. All relative though.

I would go to Home Depot and get some ¼ inch TapCons with flat heads. TapCons are hardened screws that cut their own threads into masonry .Use the TapCon drill for the holes and attach through the stone. Countersink the holes in the brackets for the screws and cover with a decorative cap. Fast and easy.

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If you are having doubts about the material you are fixing into, you could try a chemical fixing.

I have used these to mount balconies to Cornish slate built buildings with great success when other expanding and direct screw in type fixings (Your Tapcons?) were not viable or likely to force apart or crack the media being fixed into.

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There is a lot to mounting a bracket for a mantle. As said before how heavy is the mantle, what is it? What is the slate? Is it veneer like tile over drywall or a real fireplace made completely of the stone? How it is made depends on how to mount to it. Do you have pics or more info?
Rob

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As asked before, what is behind the stone...masonry board on sheet metal studs? cinder block? wood 2x4? drywall?

You may want to make a test hole to determine what you have, or inspect from other directions to determine what is going on.

With the masonry board or drywall on studs, you can drill an oversize hole and use an expanding anchor that catches the back side of the board.
http://www.fastenal.com/web/products/detail.ex?sku=50956&ucst=t
or a similar toggle anchor.

If cinder block exists behind the veneer then you can screw (tapcon) or expanding anchor into the block, or any of a number of options. This is the easiest product to deal with. If you hit a void then you can use a toggle too.

If you hit a wood stud, then you can fasten into the stud, a metal stud I would treat like a void unless I had the misfortune of hitting the web, then moving the hole 1/2 diameter is the answer.

Epoxying in a block in an over sized hole to use a lag on is an option too.

Phil

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The matle is rough cut wood measuring 4 inches thick, 12 inches wide, and 50 inches long. It is not a dense wood and so is relatively light.

It will stick out from the back of the fireplace 12 inches. The brackets will extend slightly longer than that to hold a round bar for stocking hooks.

I have been using Tapcons to screw 2x4's into concrete. I have been using the drill bit that came with the tapcon box and I can pry the 2x4's up with my hands! I my be missing something but as is I don't like Tapcons!

The base I am screwing into is as follows.
Standard 2x4 stud walls. The studs do not fall evenly across the hearth so I can't screw into the studs.
On top of the studs is 5/8" cement board. (I call it cement board...it is not sheet rock, it is the stuff you put behind/uner hearths!)
On top of the cement board is about a half inch of mortar and then about 2 inch thick slabs of real creek slate rock! The rock is face out not stacked!

I don't have any pictures sorry! I did think about taking the camera....does that count?

I like the idea of the expanding anchor....accept for the part where I have to drill such a large hole! I'm also concerned about how "drillable" real slate rock is going to be. Some of it can be pretty hard! I probably need to get a drill bit and run some test holes in some of our slate rock...it is the same stuff.

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Tapcons are meant to anchor into masonry and if you are going through wood like a 2X4, you need to drill a pilot hole through the wood larger than the screw diameter. The tapcon drill is only for the masonry and it needs to penetrate the masonry at least 1-1/2 inches. If you drill through the wood with the Tapcon drill, the screw will not snug up to the masonry. I have used them for many years and never cracked a piece of slate, stone, or marble.

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I've had some Experiance in drilling into slate and other Stones and tile. They make drill bits just for stuff like that, they will even bore through glass. They have a triangular head and no flutes, slow speed and not much force. I think their made for tile and you know that stuffs brittle. I wouldn't trust a masonry bit on it.
As for mounting go for the toggles mentioned earlier you'd be amazed how much those things can hold.

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I have been using Tapcons to screw 2x4's into concrete. I have been using the drill bit that came with the tapcon box and I can pry the 2x4's up with my hands! I my be missing something but as is I don't like Tapcons!


Use a regular drill bit with a stop or flag on it on it to go through the wood. You want this the same size as the masonry bit. It will go a lot faster too.

I have had much better results with tapcons, but I have only used them in brick and block.


The base I am screwing into is as follows.
Standard 2x4 stud walls. The studs do not fall evenly across the hearth so I can't screw into the studs.
On top of the studs is 5/8" cement board. (I call it cement board...it is not sheet rock, it is the stuff you put behind/uner hearths!)
On top of the cement board is about a half inch of mortar and then about 2 inch thick slabs of real creek slate rock! The rock is face out not stacked!


So roughly 3 1/8 material, lets call it 4 inches. Get (or make, heh) some 5 inch screws and go for it. I like HWHII's idea of gluing a cap on. Making screws isn't that hard, just need a good tap and a secure way to head the thing without messing up the shank so you can thread it.

I think you can buy square headed machine screws still...I know I have a few but they are very old and not nearly that long. Applying a matching metal finish to the screw head is not big trick.

Oh look!

http://www.fastenal.com/web/search/products/fasteners/bolts/square-head-bolts/_/N-gj4wbj&Nty=0

I really like toggle anchors too. The ones I linked can be installed, and the bolt can be removed without the fastener moving because they are "zip tied" in.

Go slow and steady. There are bits for slate and slate like materials. Might need to talk to an old roofer.

Phil
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Ok this is what I'm thinking!

The contur of the rock face has been concerning me as well as the fastenings. Since the surface of the rock is rough and not smooth, the brackets, regardless of what I attach them with, will not be square with the face of the rock. They will be canted to one side or the other.

I was talking with my dad earlier and he suggested an idea that solves both this problem and the problem of possibly cracking the slate. The idea he had makes it to where I can drill only through the mortor instead of through the rock. I really can't describe the idea, but I'll try to draw it up.

I need to get these brackets drawn in the full scale on my welding table and make a jig for the scroll work. I don't want to try to free hand three identical scrolls!

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Since this is a job that you do not want to mess up, I would suggest contacting a good stone mason in your area. If you want a desk built you get a woodworker, if you want metal brackets made you get a metal worker, if you need something done with stone you get a stone mason.

Not saying you cannot do this yourself, but since you have sooo many questions I would seek the services of a professional. Maybe even have him install it for you. Not saying you can't watch and learn.

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I'm with BigGuns on this one Dave, at least talk to a mason. My bet is a mason will be more than glad to give you advice and might just want to send some commissions your way.

I was going to suggest drilling the mortar and backing the bracket with epoxy putty to make a solid contact. A way to drill friable (fragile) stone is with a diamond bit but it's a hassle and works best with some special tooling.

Heck, the easiest thing to do might be make some dummy nail/screw/? heads for looks and use the epoxy putty to stick it to the wall. Be sure to clean any sealant from the slate at the joins first though.

Frosty the Lucky.

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Since it is a framed wall with stone veneer did the builder plan ahead and install blocking to mount the mantle to? If so then lag through the rock into the wood. If not then use those anchors from fastenal and drill through the mortar if possible. Those anchors require a larger hole. For a 3/8" bolt you need a 3/4" hole to get the anchor in. Most likely any expanding anchor behind the backer board is going to be ok. You also may consider using concrete epoxy to blue in some allthread rod and then you can use nuts behind your bracket to adjust for the irregular wall. Yes try to talk to the mason that did the job and the guy that built the wall.
Rob

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This all got me to wondering. I have some friends who want a handrail mounted to the wall beside their outdoor stairs and basically everything is solid limestone (the steps, the side wall etc.) Can you drill into that? I'm afraid to go into the mortar because it's so old (200+ years) I think it would just tear away. I'd normally suck it up and sink mounting posts into the ground, but like I said it's all limestone.

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This all got me to wondering. I have some friends who want a handrail mounted to the wall beside their outdoor stairs and basically everything is solid limestone (the steps, the side wall etc.) Can you drill into that? I'm afraid to go into the mortar because it's so old (200+ years) I think it would just tear away. I'd normally suck it up and sink mounting posts into the ground, but like I said it's all limestone.


Limestone should not present a problem using ordinary masonery bits
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I generally do not like to mount things to the rock, brick etc because after a while someone will change whatever is mounted to it. I think it is poor workmanship to do something that someone else will have to clean up or repair in the future when it is just as easy to drill into mortar and mount there. Mortar is east to patch, stone is not east to replace. Hilty hy-20 with a screen tube will do a wonderful job in most situations like this. Just my preference FWIW.
Rob

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I generally do not like to mount things to the rock, brick etc because after a while someone will change whatever is mounted to it. I think it is poor workmanship to do something that someone else will have to clean up or repair in the future when it is just as easy to drill into mortar and mount there. Mortar is east to patch, stone is not east to replace. Hilty hy-20 with a screen tube will do a wonderful job in most situations like this. Just my preference FWIW.
Rob


There is some validity to this. The other side of the coin is that often the stone is much stronger than the mortor. I tend to center mounts in stone and install work that should always be there. It someone wants to take my work out, yeah, they may have to replace a stone or two. I also have a fairly large investment in diamond core bits, so this is good advice for those less equipped.
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There is some validity to this. The other side of the coin is that often the stone is much stronger than the mortor. I tend to center mounts in stone and install work that should always be there. It someone wants to take my work out, yeah, they may have to replace a stone or two. I also have a fairly large investment in diamond core bits, so this is good advice for those less equipped.


There of course are items that are or should be a permanent part of a building, wall, etc that mounting location may not matter or are even better mounted to a large stone instead of mortar. Most things other than handrails or fences are likely to be changed at some point in the future. I have replaced things in this situation and get frustrated at the lack of thought that people can put into work when it is no more effort to do it "right". The nice thing about the hilti epoxy is it cleans with water while wet and looks like light tan grout when dry in about 20 min. Not cheap though.
Rob
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I appreciate the continued response. I talked to the client yesterday and he is wanting to go with only two brackets instead of three. (Short span, 3 would look crowded.)

Anyway, I looked at fasteners yesterday as well and picked up a dozen 2 3/4" tapcons. I'm going to do some test holes in concrete and see if I can get them to bight in good enough.....if not, I'm going with the toggle bolts.

I should be forging out the brackets today!

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