Brick
Most New York buildings from before 1900 are red brick. People say that with a sound foundation, these buildings can last 250 years. Many of them have fireplaces.
Drill brick with a hammer drill or rotary hammer and masonry bits — regular pointed bits won't do it. For safety, mark the holes for your TV mount on the bricks themselves, not on the mortar joints. Mortar can't carry a load the way brick can: it can crumble and send your TV into free fall.
In these buildings, check how solid the masonry is. If sand trickles out of the joints when you tap the wall, mount with caution. Also, level the TV with a level, not by the lines of the brickwork: after more than 100 years, these buildings' foundations settle and the walls end up uneven.
The wiring is often run on the surface. If it's hidden, ask your building's super where exactly it runs. Usually it goes straight up and down, but old buildings have exceptions.
Plaster
In the early 1900s, plaster was what drywall is today: the standard, affordable wall. These walls are built on wood studs and reinforced with thin wood strips called lath. Because of the lath, it's almost impossible to find the studs with a regular stud finder.
There are two ways to mount a TV on a plaster wall: through an intermediate plate fastened in lots of spots, or directly, using lots of toggle bolts. Both spread the TV's weight over as much of the wall as possible. Even so, don't hang big, heavy TVs on these walls. A regular 65" TV is no problem, but a huge 85" on a full-motion mount may be too heavy. For really big models, a floor TV stand is the better choice.
Before you start, it's strongly recommended to scan a plaster wall with a wire detector. Avoid drilling directly above outlets and switches.
Gypsum block and hollow tile
Blocks that look a bit like brick but are hollow and much softer: gypsum block is made of gypsum plaster, hollow tile of fired clay. You'll find them in many pre-war buildings, and in plenty of older apartment towers across the city. These walls can be as thin as 2 inches, so measure the wall's thickness to make sure you don't drill straight through.
You can make up for the shallow depth with extra mounting points. 1.75" expanding plastic anchors and screws with a couple of washers fit inside these thin walls without trouble. Drill a slightly smaller hole than the anchor. Mark the bit with tape so you don't drill deeper than you need to. Tap the anchors in gently, without hitting too hard — or you'll knock a crater out of the other side of the wall. If you like, there are also chemical anchors for these walls. Just make sure removing them later won't turn into an even bigger problem.
Even these thin walls can have wiring. It runs inside flexible metal conduit or pipe. If you hit metal while drilling, stop and pick another spot.
Drywall
The most common wall in North America. To hang a TV on drywall, find the studs with a stud finder. Then figure out what they're made of: drill a small test hole with a thin bit. If you see wood shavings on the bit, it's wood; if you see metal shavings, it's metal.
Metal studs need special anchors, which most TV mounts don't include. Wood studs take the screws from the mount's hardware kit, with no anchor. Anchors don't go into wood studs: they can split the stud along the grain.
Concrete columns and load-bearing walls
Before you start, ask your building's super whether you're allowed to drill the wall where you want to hang the TV. Structural elements are usually made of very hard concrete. They carry the weight of the whole building, and drilling into them for household needs is often prohibited.
Often these walls are only partly concrete, with drywall sections in between — and you can mount a TV on those without drilling restrictions. Just make sure the TV fits, especially if it's a Samsung Frame TV.
If you do drill the concrete itself, get a powerful rotary hammer. A regular hammer drill isn't up to the job: it may not get through at all, and you'll be making noise for way too long. Pro rotary hammer bits with four cutting edges handle hard concrete much better. Concrete walls always have rebar inside: if the bit hits steel, stop and move the hole slightly instead of drilling through it.
Use a wire detector and be extra careful with wiring in this kind of wall. It usually runs inside metal or plastic conduit. If you hit metal, check whether it looks like conduit. Replacing damaged wiring inside a concrete wall costs a fortune.

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