Putting up a 30lb wood-framed mirror

[tinpanalley]

I've got a 30 lb mirror with D-hooks on the back and cable that can take its weight appropriately. I've put this mirror up on plaster walls before but I just want to make sure because this time it's in a 120 year old building (very good condition mind you) but on a plaster wall that is above a non-working chimney, so that plaster probably has brick behind it.
I tried using a pair of hooks for hanging paintings made for 50lbs (the brass kind you nail in on a downward angle and everything seemed fine, but when I went to put the mirror up I stood on the ladder watching the hooks very carefully and the right side started to look like the plaster was bulging. Imagine a veeeery slow bubble beginning to form under the nail like it was bubbling up or lifting underneath. So, naturally something was pushing forward with the weight of the mirror so I just took it off.
I've been staring at this space above the non-working fireplace for two weeks wondering if it would work to use, instead, some lead anchors I have. They're 1.5 inches long, they're size 6-8 requiring a 1/4" masonry bit to get into the wall. I don't think there's any fear that there is anything back there other than brick and eventually open space from the chimney but I'd never be going that deep anyway. So, I'm asking... Do these lead anchors sound like they can handle the 30lb mirror to you? I'm honestly just afraid to try at this point. I've had this mirror hanging for YEARS at a time in other apartments. Both times on plaster and concrete with the regular picture hooks. I don't know why this time, I'm so freaked out.

Please help! Opinions!
Thanks.

 

[Micrornd]

Lead anchors can support the weight, but the real question is will they.
You need to get the lead anchors completely into the brick, rather than hanging part way out of it, because the screw needs to "wedge" the lead anchor in place.
Doing that will depend on how much lathe and plaster and air gap (which there should be around a chimney) is between the surface of the plaster and the surface of the brick.
Normally that distance would be 2"+.
That might be a lot of weight for a #6-#8 screw to support (considering it will be sticking out of the brick maybe 2"+) and is more than likely the reason you saw the "bulging of the plaster" on your prior attempt (the hooks were flexing and/or bending due to being cantilevered from their attachment point, rather than flush)
Does that make sense/ sound accurate?

Going to a #14-1/4" screw and anchor long enough to put at least 1-1/4" to 1-1/2" of the screw into the brick would probably solve the problem.
Or if you could hit a couple vertical studs behind the lathe that would probably work also.

 

[tinpanalley]

Going to a #14-1/4" screw and anchor long enough to put at least 1-1/4" to 1-1/2" of the screw into the brick would probably solve the problem.Or if you could hit a couple vertical studs behind the lathe that would probably work also.

Thanks so much for the thorough answer. I don't think there are any studs above this chimney. Nevertheless, I invented a little test. I took a simple, thin nail and hammered straight into the wall until I could hear and feel that I hit brick or concrete. Then I marked the part of the nail sticking out with sharpie. It turns out that there is 5/8 of an inch of plaster before hitting brick. So, questions...
1. I should be getting something that is that half an inch (a little more) PLUS an 1 1/4" in the wall?
2. What anchors are best for that kind of length?
3. So is that 5/8" of plaster not able to do any holding at all then of this 30lb mirror?

Thanks!

 

[Micrornd]

That really doesn't sound right, but you are there and I'm not so -
1. Yes
2. You could use lead shields, IF you have a lead shield setting tool (to make sure the shield is entirely in the brick) https://www.diamondtool.net/Custom/Content/Storeimages/Products/calk_in_tool_0.jpg
3. I wouldn't trust just the plaster to hold something you value.

Personally, I'd just rustle up a hammer-drill and put in 2 - 1/4" x 2-1/4" Hex Headed Tapcons (concrete screws).
They would be more than enough, but overkill is always better when hanging something you value and if you decide to move, 1/4" holes in plaster are easy to patch.

 

[tinpanalley]

That really doesn't sound right, but you are there and I'm not so -
1. Yes
2. You could use lead shields, IF you have a lead shield setting tool (to make sure the shield is entirely in the brick) https://www.diamondtool.net/Custom/Content/Storeimages/Products/calk_in_tool_0.jpg
3. I wouldn't trust just the plaster to hold something you value.

Personally, I'd just rustle up a hammer-drill and put in 2 - 1/4" x 2-1/4" Hex Headed Tapcons (concrete screws).
They would be more than enough, but overkill is always better when hanging something you value and if you decide to move, 1/4" holes in plaster are easy to patch.

What is that doesnt sound right?

 

[Micrornd]

What is that doesnt sound right?

The 5/8" plaster directly against the chimney.
There should be an air gap of at least 1" between the plaster/lathe and the chimney, even in a 120 year old house.
That's the way it is here in the south and all the old houses I've been involved with in the Midwest.

It keeps the plaster from becoming baked and brittle, but more importantly it keeps the lathe from reaching a combustible temperature as the chimney heats, especially right above the firebox.

But as I said, you have eyes on, I don't.
And if the fireplaces on that chimney are non-working, it's really just an oddity and also a non-issue.

 

[Humpy]

The fun thing about drilling into old brick walls/chimneys, that you can't really see, is you don't truly know what's going to happen until you try.

Depending on if you hit mortar, the edge of a brick, center of a brick, their condition, etc. it may just immediately crumble to pieces when you start drilling, maybe you get a good hole but things fall apart when you expand the anchor or run in the screw, maybe there will be no issues at all.

Be the bit. Pay close attention to the feedback as you go. You can feel plaster, wood, air, mortar, brick, bones, etc. as you go and should be able to sense if things are sketchy or not.

 

[tinpanalley]

Thank you guys so much for all your input and advice. I wish I could show you somehow what the wall looks like and feels like. As you said, you can feel materials if you pay attention and I don't see how that wall I hit behind the 5/8" of plaster is anything but concrete or mortar or brick having heard that distinctive high pitched scrape sound. Sure, it's possible there was air and lathe before the brick and my nail test just lsinked in between two pieces of wood lathe but then how thin would that plaster be? Seems improbable, no?

 

[mizzou]

Old houses are troubling for things like this. When I wall mounted my TV, I over-engineered the surface by placing horizontal 2x6's on the wall and securing it with huge lag bolts into studs. I then used lag screws and secured the TV mount to the wood boards, but also with enough length to go through the boards and into the wall.

Is the mirror going to overlap the area of the chimney? 30lbs is probably a big mirror, I would just do something like lay 1/2" plywood or 1x4"s on the wall and then secure the mirror onto the wood. It should be wide enough to conceal the wood.