Fixing a 2x10 floor joist

[pspe]

While renovating a room in my 4 year old house I noticed that the floor has a slope of about 1" within 4' in one corner. Taking a closer look in the basement under this room, I noticed that 3 floor joists (16 feet long) have a cut in the center about half way through (on the under side). The builder "fixed" it by nailing one 8 foot long 2x10 next to each of those. Obviously not a good solution...

And shame on me for not noticing 4 years ago.

However, I can not un-ring the bell. Now I would like to repair it - appropriately.

Should I:
a) lift the joists (using a jack) one by one the appropriate amount and nail a 2x4 to the "notched" 16' long 2x10's from the bottom? (To make an inverted "T" beam)
b) lift the joists, slide in new continuous joists and remove the "old" ones? That would be rather involved since gas and electrical lines are going through the joists.

If option a), should I calculate my nail spacing such that the inverted "T" beam would have the same amount of deflection as a comparable 2x10 based on L/360? Would I need to add a 2x4 over the entire length (16ft)? Or how can I calculate the necessary length required for the 2x4? Would it be as easy as just decreasing the nail spacing by half if I would use an 8 ft long 2x4 as long as I am not splitting the 2x4?

Thank you for any advice.

 

[racookpe1978]

Pass us a photo of your current situation, please.

Any drywall problems/settling upstairs?

Any indications the floor has cracked at the "slope point", or is the concrete floor actually good? Or just assumed good? (My "sloped floor" of just about the same size and condition was caused by a tree root being covered over by plastic and the concrete poured right over the exposed root. Net? A long strip (future crack!) right over the root all the way across the room where the poured concrete was less than 1/2" thick.)

 

[pspe]

racookpe1978:
Attached is a picture.

I found relatively small drywall cracks in 2 corners, only about 1 to 2 inches long which I assumed to be a result of "normal" settling. But in one room upstairs, where the ceiling meets the wall is about a 2 ft long crack along that edge.

The basement floor (concrete) I would say is fine, no issues.

 

[msquared48]

I would nail a metal tie strip - 1.5" wide - of appropriate length, gage and nailing to the bottom of each joist after shoring.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[CTW]

If I'm seeing the perspective of the picture correctly, it appears that the first joist in the foregroud had a kerf cut in it. It's not all the way through the joist and there is not an extra 8 ft 2x10 nailed to it. The darker joist behind this one appears to be the 8 ft long 2x10 which was added to the cut joist. This cut appears to be all the way through the joist. But there also appears to be two other joists sistered to it. So there are four 2x10's nailed together.

Is that right?

Pull a string between the top of the walls in the basement and see how the string line differs from the bottom of the joist. If there is a 1/4"/ft slope on the floor above, it will show up below.

With the information provided, I'm not convinced that the joists are the problem. Have you checked the foundation for settlement?

 

[HouseBoy]

It seems that nailing a 2x4 or a steel strap to the bottom of a joist will be difficult to do so enough to achieve sufficient shear transfer. Haven't done the calculation but just guessing.
In addition, especially for the metal strap, I would think some form of "pre-tensioning" or other "pre-loading" to get the tension into the strap will be needed. MAYBE this can be accomplished with by jacking the joist up prior to installation of the strap.
The 8 ft pieces that are in place now MIGHT be sufficient IF they can be attached to the original joist in a manner that is sufficient to develop the bending moment that is present. A similar connection would be needed on each side of the crack. I would start with 2 or 3 bolts at each end of the 4 foot distance of joist piece that is on each side of the cut. (4 or 6 bolts each side of the cut or 8 to 12 bolts total on each 8 ft piece that is scabbed in place)
I'm curious how the cut is in the middle but the slope is within 4 foot of the corner. If i understand things correctly, I would expect the slope to be more or less centered

 

[Stillerz]

Is the floor sloped? or Sagging?
Big difference here.

 

[cntw1953]

How the joist ends are supported? Will you be able to jack up adjacent joists and release and flip the joist one at a time, so the cut will subject to compression rather than tension? Just a little crazy thinking.

 

[woodman88]

Personally, if it was my house given what I paid for it, I would remove the pipes and ducts to nail new joists (of the required grade and spanning from inside of bearing to inside of bearing) to one face of the cut joists. Jack up the joists so that the new joist bottom side matches the cut joist bottom side. Connect with a cluster of 30-10d common nails (0.148" dia.), for a 55 psf total load at 16" o.c. maximum joist spacing, at each end and 4" o.c. staggered along the length. Also place a bead of floor glue on top of the new joist.
If you used a 1.5' wide metal strap like a Simpson CS14 at a 50 (40 Live and 10 Dead) psf total load, the joists would need to be 8" o.c. For a greater loading or spacing a 3" wide strap would be required. Nail one half to the joist and the other half to 2x blocking using the alternating nail holes and angle the nails toward the center of the 2x to avoid splitting the joists. Any nails that do split the lumber can not be counted toward the total number of nails required. Use one nail to tack the strap in place at one side of the cut. Jack up the joists at least 1/4" higher than the adjacent uncut joists. Than nail the strap (and add new nails to the add-on) onto the joist and blocking/add-ons than remove the jacks.
And please understand that you should get all the required calculations for your condition done by someone capable to do them before doing the repair. Check with your state on whether an engineer is required.

Garth Dreger PE
AZ Phoenix area

 

[jenDL]

Stillers, CTW, houseguy & I could use some clarification. If these joists are spliced in the middle, it wouldn't cause a slope to one end of the joists. Something else would be happening with the joist support. OR, perhaps you mean that the corner of a room above hits near the center of these spliced joists? In any case, spliced joists are a common fix and are not a big problem as long as there are enough fasteners on each side of the splice.

Without knowing what is going on above this area it is difficult to give advice, but I'll go ahead anyway.

If there is a wall sitting above this area of the joists, perhaps the joists are undersized. From looking at the photo, it appears the triple joist was there for a reason other than splicing one joist. I would be inclined to predict that a point load from above is hitting the floor in the wrong place, ie. not over the triple joist. More joists or alternate support would help. Have an engineer take a look at what's happening with the supports above this area.

If there are no other issues like settling foundation or bearing points, and the joists essentially have a permanent sag in the middle you could:
A. jack up the area in question and add yet another scab to one side and use MANY fasteners (try Simpson SDS screws, self tapping w/good load value.) It would be easier to alleviate any "preset" forces by cuting the nails that fasten the plywood to the joists in a limited area but this may be difficult.

B. if you could do it, cut the nails that fasten the plywood in the (I'm assuming limited) sagged area, jack up the plywood, and add a 2x6 or so scab to one side to bring the floor up to the desired level.

generally: Make sure you add a bunch of fasteners to the existing scab connections to prevent more sag. And, there is no need to remove anything unless space is an issue.

 

[pspe]

Thank you for all your input.

Attached is the picture with a few clarifying comments.

To better describe the situation and answer some of your questions:

The joists rest on both sides on parallel steel I-beams. One I-beam (A) goes through the center of the entire basement and the other I-beam (B) is only about two feet away from the basement wall. Actually the joists are about 20 ft long, with 16 feet from I-beam (A) to I-beam (B).

The two notches in the picture are 8 ft from I-beam (A)(in the center of the joists). The notch on the third joist is about 10 ft away from I-beam (A).

I am pretty sure there is no issue with the basement concrete floor. It slopes somewhat toward a floor drain, obviously intentionally. The I-beams are horizontal.

On my first floor two rooms are sharing a corner towards the center of the house (let's call that corner "C") and this corner is adjacent to the hall way. "C" is the "deep" point. "C" is about 5 ft away from I-beam A and 7 ft from two joist-notches and 9 ft from the third notch. The two rooms are open to each other and the hall way (very open floor plan). "C" is inside a coat closet that supports three headers (since both rooms and the hallway are open) and the upstairs walls (don't know if those are load bearing). So in short, quite a point load. The headers and ceilings are relatively horizontal, but the first floor floor slopes to point "C" by about 1 inch within a 4 ft diameter circle.

I measured how horizontal the floor on the 1st floor is using a laser projected plane. Besides the 1 inch dip at point "C", it also turned out that there is a slope towards the 3rd joist that has a notch. I could confirm that by holding a straight 8 ft long strip of plywood against the joists in the basement. That joist is parallel and about 2 feet away from the possibly load bearing wall coming down from the second floor.

With everything I learned from your responses and my measurements, I think I will leave notch one and notch two (shown in the attached picture) be and concentrate on the joist with the third notch. I will think a little more about it, but might jack up the joist and add another sister joist to it with lots of fasteners (possibly using bolts).

 

[jenDL]

well, pspe,
16' span for a 2x10 is pretty far and some deflection will be inherent.

Yes, definitely repair the third split joist, but I'd also add another scab to "joist 2". The "repair" has a knot in a bad spot-they should have at least put that knot on the top(I had thought it was already tripled but your new photo was better)

They just don't build things like they used to.
Good luck.

 

[cntw1953]

Another crazy suggestion:

1. Place 6 posts, one each besides the notch, with wedge plates.
2. Carafully release and remove the 8' long 2x10's.
3. Progressively lift up the defective joists, from the one deflect the most towards the least, until reaching the desirable elevation.
4. Place wood joist metal plates on both sides, and same length metal strip on bottom of the joist. (I wonder if there is pre-fab metal channel available for splicing wood, that will be great)
5. Re-set the posts to snug-thght position for a few days.
If no pressure on the posts after that period, you are done. Otherwise, you would have to put back the 2xs.

The above procedure assumes the joists are in decent condition after 2x10 removal, and the metal fittings are readily available from hardware stores. And it is some thing I will try on my own home for similar situations.