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Old 07-28-2009, 03:26 PM   #1
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Can a joist be cut to make more headroom?


I was wondering if there is any way to cut off 3 to 4 inches off of a joist in the basement and reinforce it with some sort of framing? Im installing a bathroom and will have to raise the tub 8 inches. If it were possible to cut the joists above the tub the extra inches would be priceless. Basically, the idea would be to cut off 5'x3" or 5'x4' strips off of 3 joists.
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Old 07-28-2009, 03:27 PM   #2
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What size are the joists?
What is above that they are supporting?



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Old 07-28-2009, 03:50 PM   #3
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Quote:
Originally Posted by Leoskee View Post
I was wondering if there is any way to cut off 3 to 4 inches off of a joist in the basement and reinforce it with some sort of framing? Im installing a bathroom and will have to raise the tub 8 inches. If it were possible to cut the joists above the tub the extra inches would be priceless. Basically, the idea would be to cut off 5'x3" or 5'x4' strips off of 3 joists.
I would be interested why you need to raise the tub 8". That doesn't seem to be the best way of doing the job.
Cutting the joists are a no, no. They're sized and installed that way for a reason.
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Old 07-28-2009, 06:54 PM   #4
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I have to raise the tub 8 inches because my sewer line is above ground. I will be using a maserating toilet unit (sanibest) and need to raise the tub in order to gravity feed into the unit.

As far as the joists are concerned, I understand their purpose and function. But at the same time I am wondering if there is any way to create additional support around them that is less than 8 inches.

The area that I am talking about is directly underneath my dining room. The joists are 8x2 and come directly off of the main support beam that runs down the middle of the house and extend to the perimiter support beam.
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Old 07-28-2009, 07:01 PM   #5
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A 2x8 joist is 7.5", taking 3-4" off would reduce it to a 2x4
That would severely reduce its load carrying capacity
You could use steel to reinforce these
But would probably have to be engineered

How far do the 2x8 joists span?
Are they 16" on center?
Only a floor above these - not a wall?
A 2x4 can only span around 5' 8" depending upon the wood



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Old 07-28-2009, 07:36 PM   #6
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if the bathroom is only to be used by the mother-in-law......

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Old 07-28-2009, 07:44 PM   #7
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They are 16" on center and they span 22'. The basement is a 22' square.

What exactly do you mean by engineered?
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Old 07-28-2009, 07:55 PM   #8
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You would need an engineer to size a steel beam to replace the 2x8 joists
And 22' is a verylarge distance to span with a 2x8
Are you sure there isn't a support beam in there somewhere?
A 2x8 will normally only span around 12'



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Old 07-28-2009, 08:02 PM   #9
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22 foot span? 2x8's? There has to be some missing information.

I have a homework assignment for you:

1. Using a tape measure, measure the exact dimension of the joists, width by height.
2. Walk down there and tell us if it's one big room, or if it's partitioned off into a couple rooms. I'm thinking there has to be a couple columns down there supporting the midpoint of the joists.
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Old 07-28-2009, 08:13 PM   #10
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wood I-joists or floor trusses are engineered. You can cut the whole center out of a wood I-joist in most cases, but you can't cut the bottom of it out. If you cut a joist out and the kerf is in the clear span, it will crack or break. There are online span calculators available that you can figure your joist requirement with, but I can tell you that 2x6 is pretty much the smallest for floor joists over. That's 5 1/2" deep. Your basement is overall 22' with a beam over the center, so your span is only 11' on each side. It doesn't look like you can alter your joists, unless you want your family to collapse your floor during dinner one night.

I just paid a plumber to break my concrete floor and run drainage for a new full bath and laundry room and it was WAY too expensive. I think someone with lots of patience and some spare time could do the job in a couple weekends if they had some help. The difference between a macerator and all the gear vs. breaking concrete and doing it the regular way yourself, well the old fashioned way is cheaper. If you pay a plumber to do the drainage, like I did, you probably would come out cheaper with the pump. What about just breaking out enough concrete to get the trap down into the floor, might get you 4" extra?
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Old 07-28-2009, 08:33 PM   #11
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Quote:
Originally Posted by NailedIt View Post
wood I-joists or floor trusses are engineered. You can cut the whole center out of a wood I-joist in most cases, but you can't cut the bottom of it out. If you cut a joist out and the kerf is in the clear span, it will crack or break. There are online span calculators available that you can figure your joist requirement with, but I can tell you that 2x6 is pretty much the smallest for floor joists over. That's 5 1/2" deep. Your basement is overall 22' with a beam over the center, so your span is only 11' on each side. It doesn't look like you can alter your joists, unless you want your family to collapse your floor during dinner one night.

I just paid a plumber to break my concrete floor and run drainage for a new full bath and laundry room and it was WAY too expensive. I think someone with lots of patience and some spare time could do the job in a couple weekends if they had some help. The difference between a macerator and all the gear vs. breaking concrete and doing it the regular way yourself, well the old fashioned way is cheaper. If you pay a plumber to do the drainage, like I did, you probably would come out cheaper with the pump. What about just breaking out enough concrete to get the trap down into the floor, might get you 4" extra?

You did exactly as your name states: You nailed it. There is a support beam that is 5.5x7.5 that the joists rest on. Each joist spans the entire length of the house and they come out about 11' on each side. My house was build in 1924.

I considered breaking up the floor but the quotes I got were way too high. I think I can do what you mentioned as far as breaking out some of the floor directly under the Ptrap. Im just going to have to be very accurate with my measurements. I dont want to have to make a bigger hole than necessary.
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