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Copied from plumbing thread with possible carpentry issues. Cut floor joists??

Copied from plumbing thread with possible carpentry issues. Cut floor joists??


Old 07-11-12, 07:29 AM
Thread Starter
Join Date: Jul 2012
Posts: 115
That's very helpful and gives me a handful of things to research.

From what I can tell, the laundry & kitchen sinks drain down that 2" pipe to the 3" stack. I'm pretty sure the pipes were put in when the house was built (and not an afterthought).

I believe the builder of this house lives close by. The house was built in 2007, and chances are that I can get a hold of him. I also have a call into the city to see if there were plans filed that could help.

I'm going out of town for a few days, so if I don't respond for a bit, that's why. But, I'll make sure to keep this thread updated so it doesn't just hang out there incomplete or unresolved. For the time being, below is a video clip of the other plumbing pipes in more detail...in case they show anything nifty. There are a couple pipes I'm unsure where they go, and may be for vents.

Last note... I'm not in a rush to add this bathroom. The upstairs alone is bigger than my wife and I (and 1 baby coming in September!) need, and we're living the dream with the 2 bathrooms we have there (just came from a shoebox house with 1). Considering this, I want to do this right, even if we need to wait, save, etc to avoid messy hacks.

I really appreciate your advice and I've learned a lot already through what you've said and what you've prompted me to research.

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Old 07-11-12, 09:51 AM
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I copied post #1 from the plumbing forum for any carpenters to take a look at the cut floor joist. Any concerns? Watch video in post #1.

Here is original thread.


These were my comments from my last post at the plumbing forum from the link above regarding this post. Added for continuity.

Issues as I see them.

At 1:27 mark in video. The tee for the vent that goes back in the wall is installed backwards.

At the 3;19 mark. That is the main vent. Should go all the way to the roof.

At the 4:39 mark, what is behind that steel door and what part of the house is above it?

If that is the only baths and the home is one floor, your best bet is to find a way to get up into the attic. Go in the attic and find that 3: line at the 3:19 mark. Try to look down the side of the pipe to see if the pipe is a dead straight run. Often you can drill a hole next to that pipe and run a 2" line from attic to basement. Often the space for that pipe is furred out and/or chased.

Also I hope one of the resident carpenters will look at this video regarding those floor joists. I know you can cut some webbing but when the cords are cut I believe there are structural issues.

This is not a very good pipe layout and the blueprints may have not been drawn with the plumbing in mind. The floor joists should have been designed for example that I toilet would not fall right on the chord or in between two joists.

Just my opinion. I will forward this to a carpenter to take a look.


Last edited by lawrosa; 07-11-12 at 11:37 AM.
Old 07-11-12, 12:36 PM
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OK, if Mike has got you covered on the plumbing stuff, here's my take on the wood butchering. You cannot cut through the top chord of an I joist. This was done at 3:31. From that point in the video to 3:39 you see almost all the webbing of the trusses eliminated in order to run the plumbing. There is virtually no support at that point vertically. The double I joists were in the plans (or not) to preclude what the architect was aware the plumbers may do. It didn't work. They cut through virtually all the webbing in most of the joists under the plumbing area. Had they limited their cuts through one joist and not the next one close to it, you would be fine. Bottom line the floor is weak. Any tile in that area will crack due to deflection. The only way to help this is to build a wall under the major offensive cuts. There are knockouts like at 2:26 for the electrician and plumber to run supply lines. They must limit their cuts for drains to the middle of the web and not exceed 1/3 of the total mass (unless their criteria has changed). I know it is after the fact, but if the HVAC had to hang under the joisting, why couldn't the plumbing? I would have sacrificed 3"- 5" of head room to have a sound floor than to try and hide it all and make the structure weak. Building a support wall to hold everything up is the only alternative. Be creative and work around the support wall. Maybe make a closet in that space.
Measure floor to joist across the room. I believe you will find this area is probably 1/2 to 3/4" lower than the rest due to sagging. Please prove me wrong.
Old 08-03-12, 10:41 AM
Thread Starter
Join Date: Jul 2012
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thanks, and sorry it's taken me awhile to reply here.

I measured the floor joists, and at first found they were about 1/2" lower in the middle, but then I noticed that water tends to drain away from the middle slightly, indicating that the concrete is a bit higher in the middle, throwing off that measurement. Even where that big support beam is - that's still 1/2" "lower" than the sides of the house. I'll have to take a good straight edge, fishing line or something to help see if there's a slope or not.

Interestingly enough, the two upstairs bathroom doors are the only ones in the house that don't close quite right

I did notice that anywhere the top of those beams were cut out for plumbing, there was a beam alongside it that the top was still in tact. in some places, the beam was fully in tact, but in others (like 3:28), the other beam had a hole cut through for the pipe, but the top wasn't cut out like in 3:31.

On this cutting-holes note...
I installed 24 can lights, and was able to utiize the existing holes used for wiring. Next up, I'm installing some accent lights and mounting speakers in the ceiling - am I pretty safe to drill 1/2" - 3/4" holes that are closer to the walls/supports?
Old 08-03-12, 02:26 PM
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Interestingly enough, the two upstairs bathroom doors are the only ones in the house that don't close quite right
BINGO! Measure the joists with a verifiable straight edge with a level. Looks as if they tried to "save" a disaster waiting to happen. Even though they left the top chord on the IJoist, they denigrated it by cutting mostly through the web.
On cutting for your wiring, the web of the beam will have knock outs for electrical. All you have to do is hit them with a hammer and they will pop out. They are in line with each other so it makes it easy to run your wiring. If you need to run wires closer to the walls, make sure your drilled holes are in the middle third of the web.

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