I'm trying to install an outdoor motion triggered light. I'm trying to drill holes for anchor inserts and I can drill through past about 1/2" in some places.

Please see the picture. You'll see a series of holes in a grid pattern. Some of it was from marking the mounting holes and some of them are discovery holes. I was trying to see if there are other places that are easier to drill through.

Do I need special bits? I'm using a generic drill bit. Ive had these forever and they've worked for all purposes until now. I'm also using a battery powered drill.

What am I hitting? Am I drilling into metal? It seems like something super hard. It is some sort of metal bracing? Or am I just in a super reinforced area of the house? It's basically where in a corner of the house. I didn't notice any concrete or bricks when I was exploring the attic. This house was built in 1939. Am I just hitting some really dense wood?

I also have at attic. See second picture. Maybe what I'm hitting is the "floor" of the attic?

I've also just tried to drill on the wall that is perpendicular to it. I've also moved up a foot or so (maybe clearing the attic floor) and also in 5 feet from the corner.

drilling attempts side of house showing attic level

2 Answers 2


Hitting something super-hard means don't drill there.

Normally pipes and electrical cables are run far from the edge and close to the center of studs. This is so you can safely drill 1-1/2" onto any wall's skin surface to install screws, anchors, etc.

When it is necessary to place electrical wires or pipes just under the skin surface, they are required to put steel plates there as guards, to prevent someone from drilling onto the pipe or electrical wire.

The idea is the person drilling will hit an unexpectedly hard surface, and think "this is probably one of those".

  • Maybe I'm getting very lucky because now I'm drilling on the wall on the left in the picture (the one that is perpendicular to the main wall in the picture. I've actually moved 5 feet in from the corner. Should I be using some sort of stud finder? I have one that slides on interior walls but when I tried it on stucco it was just constantly beeping.
    – milesmeow
    Commented Jan 30, 2017 at 0:16
  • So you're saying that if nothing is in the way, a normal drill bit should suffice?
    – milesmeow
    Commented Jan 30, 2017 at 9:10
  • 1
    Yes, that's what I use. I use common HSS or cobalt bits for both wood and metal. I can only imagine you're hitting something weird like metal grating used as lath. Commented Jan 30, 2017 at 19:06

It depends on the wall construction material. If it is block construction, it may just be that your drill/drill bit are not of the correct strength. You'll need a masonary bit and a hammer drill.

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