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strengthen cut joist


goldym's Avatar
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06-02-11, 01:19 PM   #1  
strengthen cut joist

A joist below my bathtub was severely cut for the bathtub drain plumbing:
You can see where it rests on the sill plate at the right. There's only about 2" of joist left at the sill plate.
The bathtub is out. The vertical stub went up to the bathtub overflow. The bathtub sits perpendicular to the joists, so the drain is between joists.
This would have been done 50 years ago. There's a crack at the righthand corner of the cut.
I'd like to strengthen it, partly because I'll put in a stone or tile floor and I don't want it to crack if somebody takes a bath and the floor sags.
Someone suggested attaching steel angle - an "L" shaped beam - on both sides of the joist, with the leg of the "L" sticking out horizontally. That sounds like the best idea since it wouldn't conflict with anything else in there.
How thick should the steel angle be?
The joist is sagging about 1/4" at the LH side of the cut. Can some of that sag be taken out before attaching the steel angles? I don't know how to do that.
The joist is over my garage. Someone suggested putting a 2x4, cut 1/4" longer than the distance between my joist and the garage floor, and hammering it into place as a temporary support. Would that be a good way to take the sag out of the joist?
thanks
Laura


Last edited by goldym; 06-02-11 at 01:43 PM.
 
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Nestor's Avatar
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06-02-11, 08:48 PM   #2  
Laura:

I just don't see any good way of strengthening that joist with the drum trap (the big cylinder on the right) in place.

About the only fix that comes to mind is to replace that drum trap with a modern P-trap, and use an offset 1 1/2 inch tub drain (along the line of the 1 1/4 inch sink drain shown below):



to clear the joist so that you can fasten either a sistering joist or a steel plate to the side of that joist.

Unfortunately, wood does gradually bend if there's a force applied to it. So, the bent shape of your joist is it's new shape, and I'd be concerned that using a 2X4 to try to bend it back into it's original shape is likely gonna do more harm than good.

If I were you, I'd consider that this joist has lasted 50 years the way it is, and what might be the best way forward is to simply drop the plans for a ceramic tile floor in this bathroom and opt for sheet vinyl flooring instead.

 
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06-03-11, 04:25 AM   #3  
I think a way can be found to do what she wants to do. I don't know what all your limitations are, but maybe you can treat that area like it was a stairwell. You would do that by sistering the two joists on either side. Then cut the your damaged joist and add a double header to transfer the weight to your new double joists on each side. I'm sure the more expert guys here will be able to comment on my idea and offer others that will work.

 
goldym's Avatar
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06-03-11, 08:25 AM   #4  
@Nestor, Do you know of a specific way to redirect that trap into the space between the joists? Specific plumbing items to use?
I talked to my plumber this morning and he said he hadn't found a supplier for such plumbing.
The joist could be headered off but that would mean making holes in the header for the copper pipe.
That's why, if the idea of attaching angles would give the joist enough strength, it's best. No re-routing of copper pipe. I would just have to drill holes through two steel angles and the joist, every 4 inches or so. It seems best to drill each hole through both angles, so fewer holes are drilled in the joist. The holes would be staggered.
I would need a C-clamp with a 6-inch gap to hold the angles on, but such a thing is probably available.
Laura

 
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06-03-11, 10:04 AM   #5  
Posted By: Nestor Laura:

Unfortunately, wood does gradually bend if there's a force applied to it. So, the bent shape of your joist is it's new shape, and I'd be concerned that using a 2X4 to try to bend it back into it's original shape is likely gonna do more harm than good.

If I were you, I'd consider that this joist has lasted 50 years the way it is, and what might be the best way forward is to simply drop the plans for a ceramic tile floor in this bathroom and opt for sheet vinyl flooring instead.
Yes, I'm wondering if the bend could even be taken out of the wood, now. I think the permanent deformation of wood happens over years, and jacking it back up at the bend, might just lift the joist off the sill plate.

It shouldn't get in the way of a tile or stone floor. I would just need to stiffen it in its new bent shape.

Laura

 
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06-03-11, 12:19 PM   #6  
Sending copper pipe through a joist is not a problem. You can drill small holes in the center of the joist and not reduce its carrying capacity. I believe the limit is 1/3 the dimension. The trouble arises when plumbers hack huge notches like you have. The same thing occurred in my home for bathroom plumbing and was repaired prior to my purchase.

 
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06-03-11, 01:55 PM   #7  
Posted By: drooplug Sending copper pipe through a joist is not a problem.
I know that. It's easier not to, though.

 
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06-04-11, 10:35 AM   #8  
Posted By: drooplug You would do that by sistering the two joists on either side. Then cut the your damaged joist and add a double header to transfer the weight to your new double joists on each side.
Laura,

drooplug has given you the only viable advice that a building inspector would approve. The notched area might as well be completely cut out. The cut ends of that joist would then get headed off and tranferred to the adjacent joists. Depending on their size and span those adjacent joists may or may not need to be sistered.

Doing things right is not about doing what is easier. And you probably won't get advice here that goes contrary to standard building practices and codes.

 
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06-05-11, 01:16 PM   #9  
I realized that the joist can probably be sistered with a 2x10 behind it. It would require getting the plumbing - drum trap etc. - out of the space where the sister would be, but I'm pretty sure that can be done.

 
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06-05-11, 02:24 PM   #10  
The sister would extend from about 2 feet past the cut part of the joist, and rest on the sill plate. Does this seem adequate?

 
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06-05-11, 03:02 PM   #11  
No. It needs to be the full length of the old joist.

 
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