Plastic anchors in concrete?

[tinpanalley]

Can I use plastic anchors to fasten a 35lb mirror to a concrete wall? I need two screws.

I go online, I try to research what works best in concrete, I see half the sites saying plastic anchors are fine, the other half saying one must ONLY use metal anchors, wedge anchors, etc. Let me know if you need further info.

 

[Paperdoc]

Yes, plastic anchors of the right size should do. I'd go for larger anchors and screws if you can. BUT I will say that I would PREFER to use a more secure type for that weight, although I seem to "over-engineer" such things. For example, I am going to attach an end fence post to a concrete wall and I just bought two pairs of old-style lead plug anchors in preference over plastic. They were harder to find. The mainstream mass-market hardware / building shops had none of those, but I found them in a locally-owned hardware store that has been around for decades.

 

[tinpanalley]

Ok, thanks for your advice.
This all started with me trying to use concrete screws, because I had done that in one of our last apartments on a concrete wall above a fireplace and it had worked fine. But for some reason, the screw wouldn't go in the pilot hole, so when I tried to clean the hole out a bit gently with the drill bit the screw was then going all the way in and not grasping anymore. So that's when I thought, forget it, I'm getting anchors. So I knew I had plastic ones rated for 40lb. That would effectively be enough with 18lbs on each screw. And they even say they're good for masonry, but then as I said, I started looking around online as I like to do to verify DIY things and I saw half the people practically ridiculing anyone who dared use plastic anchors for heavy applications and that metal ones were the way to go. So... here I am.

 

[mindless1]

35lbs is nothing for plastic anchors. Just don't oversize the holes.

 

[tinpanalley]

35lbs is nothing for plastic anchors. Just don't oversize the holes.

Ok. The part that scared me was people saying things like, "plastic anchors are simply not a good long term solution" and that in anything but super smooth parking lot concrete they weren't reliable because of masonry having a crumbly powder that can cause problems with plastic anchors being able to hang on. I understand that a mirror is purely downward force but I just wanted to see what people here thought.

 

[jmagg]

When I want use Tapcons and drill the hole too large in solid concrete, I put a piece or two of 9 wire in the hole. If plaster, hollow wall butterfly anchors.

 

[mindless1]

... weren't reliable because of masonry having a crumbly powder that can cause problems with plastic anchors being able to hang on.

It's the crumbling while drilling that is the main issue, best to use a little undersized drill. It's easier to enlarge the hole with a larger drill if you can't get the anchor in, than to have to put epoxy in an oversized hole.

 

[tinpanalley]

@mindless1 @jmagg @Paperdoc
Just wanted to put these photos here to show you guys what kind of wall I'm talking about. This is what I'm drilling into and trying to mount on. It's not that super polished dense concrete they use frequently in those exposed concrete condos and in modern parking lots. But it's masonry for sure, cold to the touch, etc.

So the problem I have, as I was saying, is that the hole I put the concrete screw into has been made big enough for the screw to sort of go in and out loosely because I was finding I couldn't screw it in and tried slightly shaving down the hole with the drill. It just occurs to me I should have used the hammer drill feature to screw in the screw. Might have worked then. Can the hammer drill function on a drill be used just for screwing in a screw like with an impact driver?

 

[mindless1]

You completely lost me. If the hole is too loose, put some epoxy in it.

Part of the confusion is you're talking about a 35lb mirror but then show us an outlet? Does not compute.

 

[tinpanalley]

You completely lost me. If the hole is too loose, put some epoxy in it.

Part of the confusion is you're talking about a 35lb mirror but then show us an outlet? Does not compute.

I thought it was pretty clear that I've removed the plates from an outlet "to show you guys what kind of wall I'm talking about". Sorry, thought it was self evident. I thought it might be interesting to see what kind of wall I'm working with.

 

[jmagg]

I thought it was pretty clear that I've removed the plates from an outlet "to show you guys what kind of wall I'm talking about". Sorry, thought it was self evident. I thought it might be interesting to see what kind of wall I'm working with.

It looks like 3 coat cement plaster. Hollow wall anchors are rated by weight on the package, so that would be your guide. Hole diameter is important with hollow wall anchors which will be advised on the package. Butterfly anchors open after inserted into the hollow wall behind the plaster and are tightened with a machine screw so they cant pull out without removing the screw. Butterfly anchors require a fairly large hole in order to get the butterfly through. I wouldnt use wire in the hole since the wall is only 3/4 in thick.

 

[mindless1]

I thought it was pretty clear that I've removed the plates from an outlet "to show you guys what kind of wall I'm talking about". Sorry, thought it was self evident. I thought it might be interesting to see what kind of wall I'm working with.

Sorry, was sleepy and could not see the finer details if your pics, that it's hollow, not a full thickness concrete wall. I agree with jmagg to use butterfly anchors.

 

[tinpanalley]

It looks like 3 coat cement plaster.

Hey, first of all, thanks for the nod to my favourite blues guitarist of all time. Although, believe it or not, while it also happens to be my favourite SRV song, it isn't where I got my screen name from.

But to the issue at hand... I'm no DIY expert but this ain't plaster, and it isn't hollow. I got 5 inches in with the drill bit before I hit something that felt cavernous. I've used a lot of hollow wall anchors on plaster and even cement plaster in many apartments, but a hollow wall anchor isn't going to be of any use here. I guess the photo doesn't show it well but the black space is shadow behind the outlet, not empty space. And it goes all the way inside the hole for the outlet like it was excavated out of rock.

 

[jmagg]

In solid concrete, and an overdrilled tapcon hole, I've routinely used a piece of 9 wire (or 2) to close the gap for tapcon use. Do so at your own risk, but i've not had one pull out yet. The tapcon should tighten, well tight. There should be no reason to not use a standard expanding wall anchor in solid concrete for that matter, as long as the correct diameter drill was used, as far as i can tell.

 

[tinpanalley]

I'm sure it's entirely scientifically sound, but something about wire being screwed in to the hole scares me, long-term. I think it's because I'd be concerned I didn't do it right.
I'm gonna see what metal anchors are at my hardware stores, I have a few lead ones. I just need two. I have to be honest, good quality plastic anchors feel like they'd grip the holes better. I have a box of these exact ones that we sell here in Canada that I had in mind for another project that ended up needing toggle bolts.

 

[Greenman]

Drill a hole 2" deep, drive a piece of wood into it, drive a screw into the wood, hang mirror.

 

[tinpanalley]

I've routinely used a piece of 9 wire (or 2) to close the gap for tapcon use. Do so at your own risk, but i've not had one pull out yet.

What exactly are you doing with that wire? Wrapping it around the screw threads then screwing into the hole?

 

[jmagg]

What exactly are you doing with that wire? Wrapping it around the screw threads then screwing into the hole?

I just slide the straight wire in the hole (which effectively reduces the circumference), then the screw.

 

[tinpanalley]

I just slide the straight wire in the hole (which effectively reduces the circumference), then the screw.

Ok, got it.

 

[Red Squirrel]

If I need to fasten anything to a floor that is permanent like a sub floor I like to use framing nails and rebar wire. That could be an option for a wall too, just don't pound the nail all the way in. You're not getting that out without a grinder though. So for a mirror I'd say the plastic might be fine. Just do a test pull with some pliers to get an idea how strong it is.

 

[tinpanalley]

Thank you. I went to a hardware store to look at metal anchors and one of the more knowledgable guys there told me that I could use a lead one if I really wanted but that he felt that properly rated for weight plastic expanding anchors were more likely to grip the inside of the hole better and that metal ones always ran the risk of just spinning. I wish I hadn't made that hole too big for the concrete screw.
I guess an even bigger concrete screw, 1 size up, would be an option.