I'm changing the location of the electrical service mast on my house. Is there an easy way(s) or a trick of the trade to find a stud from the exterior of the house so my lag bolts that will hold the mast brackets will hit framing and not just rough siding?

Right now, my house is sided with vinyl over 1" of styrofoam, cedar clapboard and 1x6 board siding.

I have access to the interior side of the wall, too, but I'm having difficulty translating the stud location to the exterior.

  • If you know the stud locations on the interior, why not drill your pilot hole from the inside out? You might need an aircraft bit to get enough length, but it could work, assuming the interior is accessible where the service mast is located. – Hari Ganti Mar 30 '17 at 19:33
  • @HariGanti, you should provide this as an answer. This is exactly how I would do it; find the stud from the interior using a stud finder, drill a hole through the stud to the other side of the wall using a long small-diameter drill bit, and then use that as a pilot/marker for the other holes. I would provide this solution as an answer myself, but that would be "cheating". – BillDOe Mar 30 '17 at 19:39
  • @BillOertell Well, I did, but then I noticed the OPs comment suggesting they already completed the task. – Hari Ganti Mar 30 '17 at 19:58

Plan A

  1. Find an interior:exterior reference point... a window, electrical penetration, etc. on the wall in question.

  2. Using a studfinder, or by examining baseboard nails and outlet locations, find a stud from the interior. You can often knock with your knuckles and determine to which side of an outlet the stud lies.

  3. Measure from the stud to your reference point. If it's a window, measure to clear glass.

  4. Outside, measure back from the same point.

Plan B

  1. Gently release the bottom edge of one row of siding from its retention rib near the intended mount location.
  2. Begin drilling small holes behind the loose siding at 1" intervals, just deep enough to reach framing.
  3. Once you hit a stud, drill 1/2" left and right to find the rough center.
  4. Take a measurement from a fixed point, such as the siding corner or a window.
  5. Flex the siding back onto the retention rib.

No "exploratory holes" through your siding or wounds in your drywall are needed whatsoever here.

  • FWIW, I went a sort of combo between Plans A and B! I'm still wondering if there's a method to use from the outside only, and without the test holes - basically looking for a one-and-done solution that doesn't require removing any siding. Thanks for your input! – the_meter413 Mar 30 '17 at 19:50
  • @the_meter413 It's possible to do a one-and-done, exterior-only method, but the procedure is circumstantial, at best. For example, I can see the stud locations and ceiling joists from the attic, and I can define some reference points common to the interior and exterior so I could simply measure on the outside to find stud locations, but this depends considerably on the nature of your building. – Hari Ganti Mar 30 '17 at 20:00

@BillOertell suggested I propose this as an actual answer:

  1. Find applicable stud from inside of building (with studfinder or similar)
  2. Drill pilot hole through stud from inside all the way to the outside. Perhaps consider leaving the bit in the hole or some brightly colored wire so you can spot it easily from outside
  3. Go outside and locate pilot hole

This, of course, assumes you have access to the inside wall where the service mast will be located, that you have access to decently long drill bits, and that you can find studs from the inside easily enough.

  • 1
    I'm curious why someone seems to have downvoted this answer. It's perfectly acceptable. We used a similar method to find particular locations in a house when running telephone cable when we couldn't get a location based on distances from objects that could be referenced from another perspective, say an attic. – BillDOe Apr 4 '17 at 16:43
  • Can't say (was not me, though the DV fairy evidently visited all answers) but I can guess - when you start drilling "all the way through a stud" you have just violated the standard practice of not needing to place a protective plate over wires and plumbing that are in the center of the stud (or more than 1-1/4" from the edge of it.) So you may drill right into a wire that is in no way protected from your drilling into it. Consequences can be rather severe. You may often get away with it, but unless you are opening up the drywall to look before you drill, you may not, one time. – Ecnerwal Apr 30 '17 at 3:55

Assuming you're in the USA, your house's framing is probably 2x4 studs, spaced 16" on-center. (If the house was built before modern building codes, or by some free spirit who didn't let the government tell him what to do, then all bets are off. If it's very recent, it might also be 2x6, 24" spacing.) So measure 16" from a corner (or some multiple of 16) and make some exploratory holes.

  • I've yet to see a home with exterior (or main-level interior) walls at 24" centers, 2x6 or not. Your answer doesn't explain how to find a stud anyway. Layout only applies from one direction or the other, and "exploratory holes" would be a failure of the mission as defined. – isherwood Mar 30 '17 at 19:11
  • Exploratory holes are inevitable. For me, at least - I've rarely found a stud on the first try. At least if you narrow down the search area, you won't have to make as many. – Mike Baranczak Mar 30 '17 at 22:54
  • I've never seen a 2x6 24" wall either, but I've read about them - they're definitely out there. The idea is to reduce thermal bridging and increase the depth of the insulation. – Mike Baranczak Mar 30 '17 at 23:05

Remove the vinyl, foam, and clapboards in the area of interest. Look for the nails in the 1x6 boards. Mount mast, reassemble siding.


If you can locate a stud on the inside wall you can drill from the inside of the house to the outside of the house on either side of the stud. You'll have two holes on the outside and the stud will be right between them. Hopefully the bracket for the mast will hide the two holes. Now of course you'll need to patch the inside of the wall and paint it but at least you won't have a number of holes in your siding if you guess wrong.

  • There's no reason to drill two separate holes, just one through the center of the stud will do (and no, it wasn't I who downvoted this). – BillDOe Mar 30 '17 at 20:24

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