One of our clients purchased two pole building kits from Hansen Pole Buildings last year. He has the first one completed (he constructed it himself), and decided to hire a contractor to complete the second one for him.

The Hansen Pole Buildings Designer, Rachel, contacted him recently, to see how it was progressing. The client did pose an interesting question to Rachel:

“Can I drill holes into the poles for electrical and plumbing, if so how big is allowable, and how many per pole.”

Good question and one which will pertain to any form of wood frame construction – not just post frame.

One of the beauties of post frame construction is typically very little drilling, if any, is needed for electrical holes in order to run wires. Why? Because the wall framing (girts) extend or are placed so as to leave a 1-1/2 inch space between the outside of the wall columns and the siding (whether steel or most any other type of siding).

The IBC (International Building Code) and IRC (International Residential Code) do not spell out the allowable size and frequency of holes which can be drilled through structural wood members. In order to find the answer – it takes digging into the standard lumber grading rules.

Think of a hole being drilled through, as being an “open knot”. The lumber grading rules refer to these as being “Unsound or Loose Knots and Holes” due to any cause. Most structural framing (whether joists and planks – like wall girts and roof purlins or posts and timbers) is graded as Number 2.

For practical purposes, a hole up to ¼ (or just less than ¼) of the face being drilled through will be within grade in Number 2 lumber. Example: If you have a 2×4, the face is 3-1/2” across – so you can drill a hole through that face up to ¼ x 3-1/2” or 7/8”. That’s a pretty good sized hole.  The hole size is reduced for higher grades of lumber (think of it as higher grades – fewer allowable defects). In Number 2 graded material, a hole is allowable as often as every two feet (again holes must be spaced further apart for higher grades of lumber).

On a stick framed building, assuming studs every 16”- you would need to drill through every one of them for electrical holes.  With a pole building, you can just run your wiring around the post (between the post and the siding) and between the girts – so you should be able to avoid drilling any holes.

To answer the question for plumbing – you are not supposed to drill holes through a post larger than what is allowed. As long as they are small enough in diameter, you could run hot and cold pipes through it.  Again – to do this in an exterior wall is questionable.  I’d check with your local building department and get their verdict on it.  To run a waste line (larger diameter) through a post – you’d have to use larger framing in the wall, or furr in a wall to do it.

While I try to drill as little as possible (it takes more effort and tools to do so), the Code does allow for them, within reason.