How to Drill or Notch Through Floor Joists

LESLIE: Well, if you ever had a house built or just watched one come to life, you know that the framing process can be pretty exciting because that’s truly when you see the house become a house. But there’s one critical mistake that framers can make that could bring parts of your home crashing down even years later.
 
TOM: Absolutely. And here with the nuts and bolts of that is This Old House host Kevin O’Connor and the show’s general contractor, Tom Silva.
 
And Kevin, there is definitely an order of events that comes into play here when you’re framing a house and especially when you get that all-important framing inspection done.
 
KEVIN: When you order a framing inspection on a new or renovated house, there’s a good reason that the building inspector waits until the plumbers and electricians have finished the rough work. Cutting or notching beams to make way for wires, pipes and duct work can weaken the structure significantly.
 
So Tommy, what’s the right way to cut into a beam without causing structural damage?
 
TOM SILVA: I always have to watch those electricians and plumbers. Drilling and notching can dramatically ruin or weaken the structure of your building, so there are definite rules that you have to follow.
 
First, let’s talk about notching. Never notch in the middle 1/3 of the span but when you do notch, you can never go deeper than 1/6 the depth of the joist and no wider than 1/3 the depth of the joist.
 
KEVIN: And how about drilling?
 
TOM SILVA: Drilling? You can drill anywhere along the span is OK but not bigger than 1/3 the joist depth and not within two inches of the top or the bottom of the joist.
 
And if you need more information on this, you can watch a video about drilling and notching joists on ThisOldHouse.com.
 
TOM: Tommy, it sounds like Richard Trethewey and his saws awl has been causing some mischief for you over the years.
 
TOM SILVA: I have to watch him all the time. He’s dangerous. (all chuckle)
 
TOM: Tommy Silva, Kevin O’Connor, thanks for stopping by The Money Pit.
 
TOM SILVA: Thanks, Tom. My pleasure.
 
LESLIE: Wow, that’s a lot to keep straight and it’s good information to have before you build that addition or take on that renovation or even start your dream home from scratch.
 
TOM: Absolutely. And for more tips, you can watch Kevin and Tommy on This Old House and also Ask This Old House on your local PBS station. And Ask This Old House is proudly sponsored by GE. GE – imagination at work.