Balloon frame second floor joist replacement 1

[StrucPatholgst]

Have a client with an 1880's balloon frame stick home. Rear half of the second floor framing was butchered by a plumber early in its history. Ceiling below was opened to investigate a crack in the plaster, and revealed a nightmare. Joists are true 2x7.5, and 2/3rds of the joists are unsalvageable. There are 6 inch wide U-shaped notches present that cut 2/3rds deep into each joist. Second floor is 15 feet wide, with 2.25 inches of settlement at center span. Center span has a framed wall that carries the center of the attic floor. This wall is currently hanging from the attic floor (I can stick my hand under the wall from one room into the other).

I have no cost-effective option for sistering, since an earlier (1950's?) attempt was epoxied to the notches. I plan on replacing each "legacy" joist with a double 2x10 ripped to 8 inches. I'm losing about 1/2 an inch of headroom in the room below (this is acceptable to the client). As for attachment at the perimeter, I will be blocking the perimeter wall studs behind the ribbon, and supporting the new lumber off of the blocked ribbon.

At the very end, a plumber will rerun the toilet drain in 3 inch PVC through the joist bay to the perimeter wall down to the basement. Shower and sink will follow their existing path.

Question, is there an easier way to do this? I feel the existing floor is so butchered that it can't be saved. I see cracks and splits everywhere.

 

[phamENG]

Doesn't sound like it. Given the amount of creep at mid span, getting new lumber in without removing the old is going to be nearly impossible.

A word of caution on ripping the 2x10s - you technically need to regrade them to verify knot size and location is acceptable for the size of lumber you're left with. You may be better off going with a ripped LVL joist or other engineered wood product.

What about the existing ledger? Is it too far gone?

When you say blocking, are you including fire blocking?

 

[StrucPatholgst]

The subfloor will be out when the joists are replaced.

Existing ledger (the ribbon) is only 7/8 thick. Have to block it up to get 2" of bearing.

 

[XR250]

A word of caution on ripping the 2x10s - you technically need to regrade them to verify knot size and location is acceptable for the size of lumber you're left with

I have never thought of that, however, I am not going to lose sleep over the hundred of times I have spec'ed that . Will consider it in the future.

 

[phamENG]

XR - neither had I, until recently. Over the last two years I've been living almost exclusively in residential wood construction, so I started reading a bit more on the subject (I used to be mostly steel with a bit of misc. concrete) and that popped up. Combined with a several jobs in a row looking at members that should never have been used as beams with big, loose knots causing failures in girders it sunk in pretty well.

 

[dhengr]

StrucPatholgst:
The grading rules are set up so as to minimize the potential of knots, imperfections, or other mechanical property weaknesses, such as too much grain slope, within a certain distance of a bending member edge which might turn out to be a tension stressed edge. I think you can imagine what any of these defects/mech. prop. irregularities would do the tensile stress field along this edge. Ideally, we would like the wood grain to run parallel with this edge, without any interruption, within a narrow range of grading deviations. And, when you rip the edge off the bending member you remove this better material right were it’s needed/wanted, since some inferior wood qualities are allowed in the middle half of the depth of member. Thus, PhamENG’s admonition about regrading the material to the new conditions. You can probably get by with doing this ripping, if you pay attention to the old ‘camber up’ reminder, and save the best edge and rip the other edge to minimize any degrading. You may have to discard some members (or select carefully) because you just can’t rip them without ending up with inferior edges. Then, use this ripped edge as the compression (top) edge of the simple bending member.

In balloon framing, remember that the notch for the 1" ledger (the ribbon) weakens the studs, and those same studs canti. up above the 2nd floor jsts. to the double top pls. which likely take the lateral thrusts from the roof rafters. That thrust ultimately gets dumped into the 2nd fl. jsts. through the canti. moment in the studs, at the 2nd fl. This whole detail (area) becomes kinda complicated, and many times you add a second 2x block (scab) on the other side of the main stud to help take this shear and moment down into the main stud further.