Carpentry and Woodworking - Attaching leaf table to masonry wall

I'm stumped and I'm hoping one of you guys can help.

I'm outfitting my new apartment and trying to figure out how to attach to some of the walls. The apartment is a one bedroom in a pre-war building in Brooklyn. The dividing walls between the rooms appear to have studs (I've attached shelves with drywall screws with some success) but the wall between the apartment and the building's hallway appears to be masonry of some type. The exterior of the building is brick, so I assumed the wall was brick and had been covered with plaster. I can drive a screw in about 1" before i hit a solid obstacle. I've used Tapcon screws with success in the past, so I bought some and tried pre-drilling and driving the tapcons. It was extremely slow going with the drill (not a hammerdrill), and when I drove the Tapcon screw in afterwards it wouldn't bite, the masonry crumbled around the screw and came out of the hole in a fine powder.

I don't know what kind of masonry I'm dealing with here, and I don't what other options I can try to get a solid attachment. Any thoughts or advice would be greatly appreciated.

Thanks!

In most cases, there are strict rules about tenants anchoring things to the walls. As for tapcons, a good hammer drill is almost a must, as is the correct sharp drill bit. If the hole is only slightly oversize, the screws will not work. A standard drill rarely works, the bit always wanders.