Cutting hole in 8” C-purlins

[rockcrawler]

I’m in the process of installing two 24K mini splits in my shop. I want to run the lines inside the shop down to about a foot or so from the ground and then go out to the outside units. This will require me to cut a 3.5” hole in the middle of my 8” wall purlins. I just wanted to get some opinions on whether or not this will cause any issues. If so, can I weld in some kind of plate that will supply some support? I’m sure I’m wrong, but it almost seems that the wall purlins are holding the sheathing on more than anything.

These are the locations where I need to run the AC lines through the purlins. The inside units will be mounted just above that upper purlin. (Pic is from back when it was being built a couple of years ago.)

 

[drmarkr]

Center them and cut away. That's not going to significantly affect the purlin stability/strength.

 

[LXCam]

I’m with the doc, knock yourself out it’ll be fine.

 

[readhead]

The girts (purlins hold up the roof) are there to hold up the sheeting. There should be no issue with placing the holes you need for the line sets.

 

[rockcrawler]

Thank you to everyone for your input.

 

[Monza Harry]

If you are even a little worried, you could weld a piece of tubing [16 gauge would likely be more than enough "overkill"] through the hole. If the girt is say 2" tall (x 8" I think you said) make the tube 3" lg and then if you still aren't warm and fuzzy feeling plate the open side [boxed if you will]. But as said above likely fine as stated. These measures would be for your comfort mostly. Harry

 

[Beamer]

Sooner or later a wind storm strong enough to have affect will come along.
Metal buildings are generally not overdesigned. That is how they compete pricewise.
It may not be legal in your area to alter the structure without a professional signing off on it.

 

[Beamer]

The girts (purlins hold up the roof) are there to hold up the sheeting. There should be no issue with placing the holes you need for the line sets.

WIND

 

[readhead]

Without going into a long winded explanation about shapes the basics are the important parts of a shape are the flanges or cords. Of course the web does its part but the flanges are what is important here. In this situation the outside flange is in compression but more importantly the inside flange is in tension which doesn’t want to stretch. A good example is a wood roof truss. It is pretty much all holes but it can resist a heavy load because the bottom cord is in tension resisting the compression of the top cord.

If I am designing a building I can adjust the wind load and the only factor affecting the girt size is its length which goes back to how much tension that member can tolerate. The gage of the material can be increased to overcome the problem and a hole can still be put in the member.

In this case if there is a concern about wind an extra flat bar could be screwed to the inside of the girt and the additional tension would overcome the wind concern. Twenty five years of metal building experience suggests to me that this is not a problem.