What am I drilling into?

[david.hollman]

Recent project to hang some adjustable shelf units in the bedroom closet by screwing them into the old chimney bricks (the chimney comes up the middle of the closet).

So I was trying to drill holes about 2 inches deep for plastic plugs. I managed to get a few in before the drill bit hit SOMETHING which it could not penetrate - at all - in many places along the chimney (many feet apart but no clear pattern). The something was within 1 inch of the surface.

I was using a masonry bit which worked fine in other places/brick walls/etc.

I stopped drilling after hitting this in a few places, not wanting to make more of a mess if no good would come of it.

Any ideas what could be in there that is so hard? Some sort of stone or metal perhaps? I thought chimneys were just brick (1930's terraced house) but apparently not.

Thanks Dave

[Stuart B]

Could well ne a steel support across the top of the chimney opening ....like a lintel

[Harry Bloomfield]

Check the tip of the bit with a lens, usually they will collect some tiny metal particles if you have hit steel.