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Floor joist cut by plumber sagging - repair questions with pics and video

Floor joist cut by plumber sagging - repair questions with pics and video


Old 01-30-08, 08:05 PM
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Join Date: Jan 2008
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Floor joist cut by plumber sagging - repair questions with pics and video

We have a 1" sag in our floor along one joist and around 1/2" sag in the joists on either side. The low spot on the floor is in the center of the span and the floor has some bounce in it. I have located the problem and it's a floor joist that was completely cut when the house was built 20+ years ago for a plumbing drain. No support or braces were added. The low spot is where the refrigerator was located (now moved) In addition to the joist that was cut, the joists on either side of the cut joist also appear to be sagged a small amount and in the basement I noticed they have holes drilled out of the bottom 2" for an electrical line. What a mess from shoddy work.
My plan is as follows: I have a LVL board to sister to the cut joist. The LVL is a14' "2x10" and all my joists are 14' 2x8's. I am going to rip the LVL to the size of a 2x8. I plan to turn the LVL on it's side and push it over the beam in the center of the house, then slide it back over the sill plate on the outside wall and rotate it up on it's end. It will be screwed or bolted to the existing joist and PL Premium construction adhesive used. On either side of the cut joist, I will be sistering boards to the those joists as well. I plan to pull back the electrical wires that are currently running through the joists and run those down the center support beam and then through the joist cavity to the light outlet so no joist drilling is required.
There are a couple of issues/Questions:
- The new joists are 7 3/16" tall and the old joists are 7 3/32" Should I rip them 3/32" smaller or just the ends? Also to rotate them into position do I need to radius the corners?

- Screw or bolts? My Father in law said bolts might make it look like there is a more serious problem to a buyer later on if we ever sell.

- At a minimum, I am sistering the cut joist with the LVL and sistering new 2x8's to the joists on either side for a total of 3 sistered joists. The question is with the sequence for attaching the new joists. I have a 4x6 beam for jacking, 3 screw adjustable columns and a bottle jack. I would like to use PL Premium and screws or bolts. PL Premium says it has a 30 minute working time for repositioning the materials to be bonded. So do I get all 3 joists laying on the 8" side then jack up the three joists until the floor above is flat, then apply the PL to one board, turn it on it's side, clamp it together and then screw/bolt that entire joist before going on to the next? I have a feeling turning them up and attaching them is NOT going to be a piece of cake because of the sag. If I wasn't using construction adhesive I imagine I would jack up the old and new joists all 3 at the same time, make sure the floor above is level, then secure everything.

- Do I install it with the floor slightly higher than it needs to be to overcorrect the sag?

- In the areas like the stairwell where I can't slide the joists over the center beam so my options seem only to have one end of the sistered joist resting on a support wall - is this still worth doing? is there another way to support them maybe with a joist hanger or bracket?
The reason I got an LVL beam was I thought I needed something stronger than just another 2x8 joist to overcome 20 years of sag.

Thanks for any advice- here are pictures and a video to better illustrate my situation:

Video below: http://www.jumpcut.com/view?id=1BBCA...FA000423CF037A
<embed src="http://www.jumpcut.com/media/flash/jump.swf?id=1BBCA458CDED11DC8BFA000423CF037A&asset_type=movie&asset_id=1BBCA458CDED11DC8BFA000423CF037A&eb=1" width="408" height="324" type="application/x-shockwave-flash"></embed>
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Old 01-30-08, 08:48 PM
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At first glance, the problem is twofold.

1). undersized floor joists

2). the cut joist (thank you plumber.)

Looking at just the first picture, I'd suggest that you sister LVL's to the 2 good joists on either side of the cut one. (cut a 10 angle off the top edge so that you can turn it up into place without it binding on the floor.) Both ends of these LVL's must obviously sit on load bearing walls. Then cut the joist that the anonymous plumber butchered back just enough that you can head that joist off, installing a pair of short LVL's perpendicular to the end of the cut joist, placing them in hangers onto the sistered LVL's. The cut joist would then butt up to the short LVL's on each end, where it would also be placed in a hanger. 6 hangers in all. You're basically making a square box around the cut plumbing that would be roughly 30 1/2" square. Then you can throw some blocking in the box as needed, no hangers required. Nails to sister the LVL's would be sufficient. There may not be enough room to do this because of the block wall, in which case you'd have one LVL parallel to the wall, with new joists extending back onto the sill plate. Since they would be less than 4' long, hangers would probably not be required.

I would not overjack it much past straight at all, or you will put additional tension on the LVL's, which would be counterproductive, I think. Leaving some posts underneath as temporary supports would be a good idea, and they could be slowly let down and removed in the months or years to come.

I think that suggestion would pass inspections where I'm from.
Old 01-31-08, 02:04 PM
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Plumbers should not be issued reciprocating saws. Some just don't understand the trouble we went to in order to make a solid floor. Most of them I work with will at least ask for us to move framing members for them if they are in the way. Of course they can move 1 1/2" over and miss it, but we understand aesthetics, too. Forbid a toilet is not centered in the bathroom! What XSleeper said.
Old 01-31-08, 09:56 PM
Thread Starter
Join Date: Jan 2008
Posts: 2
Thanks guys for the replies.
I hadn't thought of additional lvls to beef up the whole area. I like the idea. Is it worth sistering a 3rd lvl to the length of the cut joist from the short LVL back to the center beam of the house? the reason I ask is that upstairs the lowest part of the sag is centered over the middle of the span of the cut joist sort of like this:

|--------------<-1/2" low Spot--->---------------------|

|-----------<---Low Spot Center 1"--->-----X Cut X----|

|--------------<-1/2"--Low spot ->---------------------|

Somewhat strange the low spot is in the center, but that's where the heavy fridge sat for 20+ years
Old 02-01-08, 04:45 AM
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It couldn't hurt, if you need to straighten out those small 2x8's. The most important thing you don't want to skip is to head off the cut joist and use joist hangers. The perpendicular support and hangers give it strength where it's cut so that it's not just hanging in midair with the subfloor holding it up. And you should be able to order an LVL that's the right length and size. Ripping the angle is all you should need to do to them.

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