I-Joist Repair from Curbless Shower

[drakaric]

Hi everyone, I'm ready to do a bathroom renovation but there are some things that need to be addressed first.

So for quick background, the previous owner was wheelchair bound and so they redid the bathroom to accommodate that, which involved them essentially destroying the I-joists to lower the shower floor. So over a span of 6 joists, they roughly cut about 3" down and over 3' from the end (The joists are 2.5"x9.5"x16'). With that, they ended up putting a load-bearing wall in the basement where the cuts were made and then added 2x8s for the notched side. I really don't want that wall there since I want to make a recreational room in that section since it's got plenty of room for it.

I talked to a contractor I know from my old maintenance job and he pretty much said I need new I-Joists sistered on, which I pretty much assumed but needed to be sure that was the only way, since I knew nothing about I-Joists. The installation plan will be to cut out the rim joist from the garage and slide the new joists through and nail it back in. I'll put blocking at the ends in between the joists for extra support.

So my question is: what do I do with the original joists? Is it worth trying to scab it back together with some rim board material since the new joists would be taking the load for the most part? It looks like the 1-1/8" would fit perfectly inside the webbing as a backer. I just don't know if it's worth putting more money into. I was thinking maybe doing something like that for at least the joists that will support the 80 gallon bathtub if it makes sense to - why not add the most support while I'm there? According to the original bathroom plans, they already designed it to handle a 50-60 gallon bathtub at 3' - 8' span from the end across 3 joists. I will be installing a corner tub that will span 6" - 5'6" span from the end across 5 joists.

Also, whether I scab together the originals or not, do I need to add any web stiffeners between the 2 joists for more surface area for adhesive or can I just glue the flanges together and be done with it?

I'll try to get external images linked up if necessary.

 

[e hilton]

Trying to remove the existing joists could be a problem … the plywood subfloor is nailed to the joist every foot or so. Better to just leave them in place.

 

[e hilton]

You could use a sawzall blade to cut the nails, but how would you nail the plywood to the new joists without removing all the flooring?

 

[drakaric]

I don't plan on removing the old joists, just more curious if I'm able to squeeze more load capacity from them while I'm doing the work with the new ones, or are they as good as garbage once I remove the intermediate wall?

 

[TheCommish]

Once the wall is gone you have a non compliant possibly overloaded floor system, will it fail maybe, with out more information hard to tell. If the new walls top plate is in the way to install the new joists, support each joist independently with bracing on the vertical jack for each damaged joist. Trying to gain any strength from the existing damage "I" joist in not worth the expense of the engineering

 

[drakaric]

Ok, fair enough. Does the new joists need to be butt up and adhered to the old ones? Or should I just gap them a tad and treat them independently? Just wondering if I will run into squeaking problems

 

[TheCommish]

I would check the manufactures directions for doubling joist together

 

[e hilton]

I would check the manufactures directions for doubling joist together

But he’s not doubling the joists to act as a header or the traditional reasons for a double, he is replacing the cut joist. I would try to get them within an inch.

 

[steveray]

Can you find a manufacturer? They have a lot of info on their site typically....If you are not exceeding an O.C. span, then there is not harm in leaving or beefing up the existing....

 

[bill1952]

I would think a part of this is if it's possible to fasten existing flooring to new joists or better to sister joists and rely on existing floor fasteners in that area. Careful adhesive use and maybe blocking at the cut end between webs, followed by structural screws if joist manufacturer allows. I'm not sure how easy it will be to insert new joists into a specific location.

 

[tbz]

The wall was added to support the violated floor system, as you noted,
Replacing the I-joists and returning the floor system to original design, would be one way and high costs
Adding in new structure, or sistering the I-joist with LVL's would work I think, getting them in place is another herculean task and cost.

Though it might cost you some money, I would recommend asking your contractor to ask their supplier if their local rep for the I-Joist supplier has a local engineer they can recommend to come out, and recommend a method and material plan.

Making structural changes, I believe requires a permit and I am not sure if just following prescriptive information on an engineered floor system can be accomplished without an engineer being involved anyway.

So why try and figure out what an engineer is going to have to confirm or do anyway.

Just my thoughts.

 

[drakaric]

Just to give more visualization, The pics of the notches can be found here:

Joists-1
Joists-2

I have been reading the tech spec from the manufacturer, they do have instructions on doubling up, but as mentioned above, this applies to intact joists. The original one is straight up missing the compression side at the end. There is even one joist where the tension side was partially notched for a pipe, which I cannot understand why - It's like they tried every possible way to destroy the joists as they could have easily moved the drain an inch to the side. Doubling consists of filler block with 1/8" gap at the top that spans full length with 2 rows of 10d nails 12" O.C. with 6" offset from the opposing side:
Doubling Joists

I've read up on span capabilities in coordination with the O.C. spec from the tech doc, and everything appears to check out if all I'm doing is putting in new joists next to each other. Obviously there's more to it, but it's close to original design. These joists support a bathroom and a closet floor with an interior wall that separates the bedroom.

They manufacturer resides in Canada, but I can try to reach out to them to see if they have any recommendations on retaining strength from the original joist. Otherwise, the only repair information I was able to find from some research only refers to small notches from plumbing but nothing to this extent.

 

[ICE]

New I-joist is the only way to fix this. No engineering required. No attachment to the existing joist required. Solid blocking at the ends required. Web stiffeners required. Permit, well if there's a chance of getting caught, required.

 

[SCBO1]

Well there went the I-joist warrenty!

It is written, though shall not cut I-joist!

 

[ICE]

I should add that blocking between the the old and new joists 4' on center is a good idea because the top flange is not screwed to the existing floor sheathing. You asked if the existing joists will be garbage after the support wall is removed and that's pretty much the case.

 

[drakaric]

Ok, that pretty much sums up my thoughts and intentions then. One of my concerns was the fact that the sheathing would not be completely attached, so intermittent blocking makes perfect sense. I was going to try to add construction adhesive to the top prior to setting, but I don't know how successfully that would turn out as it might just be a smeared mess, but better than nothing I guess. However, the entire bathroom floor will be exposed during renovation so I should be able to nail down half of the beams. The closet has wood floor and so I won't be touching that.

Thanks for the inputs! I appreciate it.

 

[SCBO1]

You asked if the existing joists will be garbage after the support wall is removed and that's pretty much the case.

I would agree with that summation. There only use maybe to apply drywall to the bottom flange for a ceiling.

I wonder if the material was 2x10's and they were knotched like the I-joist if we would be having the same discussion?