this post was submitted on 18 Oct 2025
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Hypothetically speaking, if he just cut a whole big enough for the pipe to go through how much better would it have been?
Much better. Imagine you’re bending something. The maximum tension is going to be at the very bottom and the max compression is going to be at the very top (this is why steel I-beams are shaped the way the are - to put the most material in the areas doing the most work). If you can put the hole in the middle you’re not impacting the structural integrity of the joist too much. You’d still have to worry about shear forces so you’d not want the hole to be too close to either end. Look up “castellated beam” if you want to see some steel examples.
Why not just use hangers? No way a metal bracket doesnt exist for hanging pipe from joists. DIY some metal wire and a screw to hold it if you have to, hang that sucker like fresh venison, but why cut existing structures?
100% a better way of doing it. I was just trying to answer the question of notching versus drilling a hole.
It's not structure, it's just extra wood
I meant structure as in existing stuff, not 'structural' as in load-bearing. Extra wood would indeed still count as 'structure' within the context I meant.
This is, however, not just extra wood. What was cut through in the picture is floor joists, which are what holds up the flooring and supports whatever is on the floor, including people and furniture. Cutting these joists severely compromised the integrity of the floor. Now instead of a squeak from stepping in that spot, it's far more likely that a loud crack followed by a fall through the floor will be the result of a heavy step.
No no no, I was being sarcastic, because this is indeed structural and not the way the text in the photo described it
Any chance you could point me to an example of hangers?
A joist hole can be no more than 1/3rd the total depth of the joist, I think that pipe is larger than that. Even if you placed it in the very middle you’d still be compromising the structural integrity.
Best to just get some hangers and a fix it to the bottom; you’re still well clear of the ground. Put in some shims near one end if it’s a drain and you have to maintain pitch; I think this is a thick electrical conduit though?
EDIT: nope that looks like 4” PVC drain pipe
Assuming it's centered vertically and not too close to the ends, then the joists would still have essentially full strength. Because the top and bottom are seeing compression and tension, there's an area in the middle that's not so critical.
A lot. Most of the strength from a beam comes from the top and bottom, because these are the parts that have to stretch or compress most when the beam is bending. The middle part is contributing relatively little for strength.
That is why metal poles are often hollow, that saves a lot of material and weight without losing much strength.
Every part of what you said is wrong.
The middle indeed provides strength, when it is intact. It prevents the top and bottom from additional deflection under load as it takes on part of that stress. That is why there are very strict rules about when and how you can cut a penetration through a load-bearing joist (which, by definition, they all are).
Additionally, metal poles are a cylinder and take an axial compressive load, for which a cylinder is a very good shape; if you tried to support a floor with a wooden cylinder as a joist and the load was lateral to its length, it would likely buckle - its whole shape is hollow so it has the same problems as a joist with the middle cut out.
I'm really proud of how confident you are.
Well I don't think it would have been possible to assemble