2x10 Repair 1

SeattleME · Oct 9, 2023

Hi Everyone,

I’m a mechanical PE and could use some advice on the structural repair of a botch job an electrical contractor did at my house. I’ve attached some photos for reference.

I have about a dozen 2x10 floor joists over my garage. The kitchen is directly above the garage. The 2x10 joists have a span of approximately 17’-6”. An electrical contractor bored 2-inch diameter holes through the bottom section of the beams all the way across my garage. He installed a 100-amp subpanel on the other side for EV charging. The holes left about 1/2” of “meat” between the lower quadrant of the hole and the bottom surface of the beam. The holes are about eight feet from one end, positioned in the middle third of the beam. In effect, the electrician turned my 2x10s into 2x8s.

I’m in King County, Washington State, where the IRC is applicable. The IRC says no holes in the upper/bottom two inches of the joist. The inspector did his inspection via camera phone (didn’t even look at the joists) and passed it. I didn’t notice the issue until after the electrician left site (shame on me - wife says it’s my fault, but then again isn’t everything).

I will be proceeding with a repair for peace of mind, if nothing else. I don’t like the idea of reducing the load capacity of 2x10s that were already probably at max span. Especially not in my kitchen where people tend to congregate during social events. I’ve contacted the contractor but haven’t heard back yet. If he doesn’t agree to pay for the repair, he’ll be hearing from my attorney. I’m a forensic engineer, and as much as I don’t like to admit it, I know several dozen.

My questions (and thanks for reading this far) are:

1. Does anyone have any experience with joist reinforcement plates like those offered by Skyline Joist Repair (

http://www.joistrepair.com)?

While they look they’d work, the company has zero certifications and makes no code compliance claims whatsoever. However, if properly installed with screws and two-part epoxy, they look like they’d work okay as long as they more than make up for the deficit in the lost section modulus of the beam.
2. Would it be better to sister two 3/4” sheets of A-bond plywood on either side of the beam? Screwed and glued, of course.
3. Should I jack and level the beams before applying the repair in order to unload the beams near the stressed area? I don’t like the idea of encountering a flexural stress failure in the beam due to lack of composite action between the beam and the reinforcement plate or sisters.

Before someone suggests placing a Simpson strong-tie over it, I’ve read multiple opinions of SE’s saying that this won’t work due to the beam’s preload and lack of composite action between beam and tie; i.e., the beam will fail in flexure, then the load shifts to the tie, and then the tie fails — and all without any apparent increase in load carrying capability. Empirical evidence appears to support this position. There is a report from the 1970s where they tested metal straps running along the bottom of a joist. The straps were installed the full length of the joists. They found it didn’t help — the straps and wood failed independently of each other.

Appreciate the advice.

XR250 · Oct 9, 2023

Your electrician is a dummy.
I can't imagine the numbers panning out on those reinforcements.
17'-6" is a long span for a 2x10.
Maybe you could sister each joist with two 2x8's?

LittleInch · Oct 9, 2023

Just a couple of observations -

1) That measurement looks more like your beams are <2 x 10, more like 2 x 9?? what's the actual width of the beam?

Also what is left is about a 2 x 6 1/2?

And in cutting away the plasterboard, he's nicked into the beam by about 3/4", right where the tension path lies?

what are those little itty bitty plates? Who banged in those?

Good luck trying insurance for something like this - not sure they insure for poor workmanship. Better off going after the inspector for passing what is clearly a bad job.

Is there any visible or measurable dip in the floor? If not there's nothing to jack up.

what's to the left and right of the beams when you look along them? Bound to be some cross bracing somewhere, but any other services?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

phamENG · Oct 9, 2023

LittleInch - it's a 2x10, which is 1.5"x9.25" from the mill, often slightly shorter after it's dried out more in service. Those little plates are just to keep the drywall guy from putting a nail/screw through the cable.

I'm with XR on the 2x8s. Off the cuff, I'd say an 8' 2x8 at each joist, centered on this spot. Then I'd run a couple of long self drilling (or pre-drilled) screws through the 2x10 on either side of the hole to keep it from splitting around the hole.

That loose knot is a doozy.

SeattleME · Oct 9, 2023

The beams are 2x10 nominal, which is 1-1/2” by 9-1/4” actual. There is about 6-1/2” material left in the beam above the holes, so the beam is effectively 1-1/2” by 6-1/2”.

I don’t see any nick's in beam where he cut away the gypsum board. That’s not an issue.

The metal plates in the photos are nail guard plates. They are required by the building code. They prevent people from accidentally driving a nail into a 100-amp feeder; i.e., they are not structural.

Deflection in the span isn’t visible with the naked eye, but I’m sure there is some as physics would dictate.

There are no other holes through this beam to the left or right. No cross bracing either, as far as I can see. There’s insulation between the hard lid and second floor, so you can’t see much.

Thanks for the response.

phamENG · Oct 9, 2023

SeattleME - 6.5" to the top of the hole, but what about the top of the cable? If you can fit a 2x8, that would be best. Might need a pair of 2x6s? Have to run the numbers to be sure, but of course that goes for either case.

SeattleME · Oct 9, 2023

Thanks PhamEng and XR250. I was afraid that a larger sister like that would be the answer. That’s a lot of drywall removal, but right is right.

I haven’t gone into a detailed FEM analysis of the Skyline repair plates, but something about those things doesn’t sit well with me.

phamENG · Oct 9, 2023

The Skylines can work, but retrofit installations can have problems as you mentioned. It's the same thing as a Simpson strap. If you don't jack the floor, then the wood has to deflect a lot more before the strap takes over. If you lay the strap in a high strength, low stretch epoxy along with the screws you might have better performance. But I'd still want to jack the floor to unload the joists before doing it.

Don't bother with an FEM analysis. The anisotropic and highly variable grain patterns of wood make FEM a bit futile in my opinion. People use it, and I guess you could get some idea of the stresses...but applying those requires an in depth knowledge of how wood works and how wood fails....something that a troubling number of structural engineers seem to struggle with sometimes.

SeattleME · Oct 9, 2023

There’s about 7-1/2” clearance above the cable.

I just went down and remeasured. The span is 14 feet. The place where they effed up the joists is at 6 feet (see photo).

I meant FEM for the Skyline bracket, not so much the wood. But you bring up exactly what concerns me. Wood failure isn’t always due to flexure stress. It often fails in horizontal shear, as well, and is prone to delamination. It makes my mechanical spidey senses tingle.

So far I’m getting:

1. Yes to jack the floor.
2. Sister two 2x8’s, one each side at 8 feet in length. Screw and glue.

SeattleME · Oct 9, 2023

I’ll load up beam boy later today to compare two 2x8 sisters vs a single 2x8 sister.

LittleInch · Oct 9, 2023

Man that looks like a pile of work and you have some obstructions in the way.

Is the weight of the extra 2 x 8's insignificant?

Just to close this out these are the 1/2" nicks evident where the guy cut the plasterboard / dry wall.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

XR250 · Oct 9, 2023

for a 14' span, (1)2x8 would be fine.
I looked at the engineering for those Skyline plates. Did not see them address the screwed connection other than calling out the allowable shear for the fasteners.

kipfoot · Oct 9, 2023

I agree with the gist of the comments. My first thought was also an 8' 2x8.

When you talk to the inspector, ask how they think the installation meets figure R502.8. Maybe you need to insist on a framing inspection not just an electrical inspection.

SeattleME · Oct 9, 2023

The inspector already signed off on it a couple weeks ago when the work was completed. I need to call him today to see if he can reverse his acceptance or do something about it otherwise. **Edit - or call him tomorrow. Apparently, they are closed due something called Indigenous People’s Day. Never heard of it.

SeattleME · Oct 9, 2023

” Did not see them address the screwed connection other than calling out the allowable shear for the fasteners.”

That’s what concerns me. Wood being wood, I doubt you’d get the full allowable shear strength out of those fasteners while under an actual load.

RattlinBog · Oct 9, 2023

Sorry to see this--not fun. Not sure if this would be helpful, but I recently completed a similar project in my old home. I was dealing with some really old issues/poor workmanship and did the structural work myself. Here's the EngTips thread: [URL unfurl="true"]https://www.eng-tips.com/viewthread.cfm?qid=502899[/url]

If you opt to do some jacking, a simple bottle jack on a wood post with a good base should suffice. Just apply a bit of positive pressure. Too much, and you'll start cracking things or have a hump in your kitchen floor. I wouldn't think your floor has experienced a lot of additional deflection since these holes were drilled.

Partial length sister joists are certainly a good option. Your biggest challenges are going to be getting adequate access between joists, working around or temporarily relocating existing utilities, and getting your new plywood or 2x lumber to play nicely with existing deflection / new lumber crown. Biggest cost for my home project was paying electricians to reroute all the wiring running through my joists.

SnTMan · Oct 9, 2023

SeattleME said:
...something called Indigenous People’s Day. Never heard of it.

Used to be known in the US as Columbus Day. Before, you know...Never mind.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

lexpatrie · Oct 9, 2023

It replaced Columbus Day, as I recall. Not that it's all that germane to the conversation.

You've got a valid issue here, what the reinforcement people are brushing past is there's also a fire issue to be dealt with, I suppose with the gypsum board ceiling you're "okay" but the 2x8 unsecured to the gypsum board ceiling isn't exactly what you had beforehand. I usually only see this degree of contempt for framing from plumbers.

I don't know why you wouldn't do it CORRECTLY, even if you think you can replace/reinforce it, why bother? Replace with 2x10s to match existing at the spacing to match existing, drill the holes where the IRC insists they go (in both joists) secure the new joists to the old joists, install ceiling. You're a forensic engineer, why create a long explanation for the next buyer on your disclosure statement versus doing what was allowed/required in the first place that met code before the electrician mauled it?

Regards,
Brian

ETA - given this seems to be romex, drill the smallest workable hole just to drive home the point of how excessive this hole drilling done by the electrician was. That looks like a 2 1/2" diameter hole. Romex is what, 3/8" and even that leaves enough space for a mouse to squeeze past it? Mice have compressible skulls they can fit through a dime sized opening. (Nowegian?) rats are the same story but it's a quarter sized hole. Your guy created a gunny sack rat run when a mouse run would have sufficed.

SeattleME · Oct 9, 2023

Thanks everyone for the responses.

Part of what I’m trying to determine is “what is the correct way?” If doing full sisters throughout is the correct way, then so be it. I’ll likely sue the electrician for damages, anyway. But I’d also need to justify the repair later on in the lawsuit.

Also, I’ll be hiring a local SE to oversee the repair. I’m not going to try to design or do it myself. I’m the type that wants to make sure the repair process is well thought out before engaging an SE and builder.

lexpatrie · Oct 9, 2023

As a forensic guy, you know that what you're supposed to get is what a responsible contractor would have done, workmanlike quality, i.e. a normal hole in the joist in the correct location and an appropriate size for the hole. While you might argue you need an expert witness to testify on the (electrical) Contractor's standard of care, or what constitutes a workmanlike job here, I think a few pictures from the code, your pictures, will quite adequately address what the jury needs to know. They can see it perfectly well that what was done far deviates from what a normal electrician would do. This is the equivalent of leaving surgical instruments inside a surgery patient. While an attorney may insist on having a doctor testify to that being a bad idea, absolutely anybody can see that's a bad idea. There's terminology for this, but I forget it. Something like expert witness testimony is useful only if it would aid the trier of fact (the jury or judge in a bench trial) understand the issues. These seem really plain. Like failing to put the drain plug back into an engine after you do an oil change.

You fundamentally don't have what a responsible contractor would have done. Anything less than what you had BEFORE is exactly that, LESS. There's your economic harm, there's your tort. You have a structural issue NOW, due to your contractor's negligence.

You didn't have an engineered house to start with, right? So while an SE might be able to tell you "what you can get away with for a lesser repair that more or less addresses the problem," from a structural standpoint, that's fundamentally NOT what you had. You didn't have a floor system that was riddled with excessive holes, patched back together, glued, screwed, sistered, nailed, no matter how scientifically it is patched together. While it can be made safe, you still have a disclosure issue when you try to sell the house. There is a straightforward way to repair the problem without bothering with an SE. IMHO. Do it right, leave the junk in there and nail to the existing because then the floor transfers load to the new joists. It also seems like this would be less expensive, take less time, etc. Sure, you're tearing down the ceiling, but you have to tear it down at least partly anyway and you want full size sheets in the repaired area.

That joist repair stuff "looks nice" but where's the ESR? Where's the engineer's seal for a proprietary reinforcing product? These guys are selling before they are really supposed to. You outside a code area, it's a shack? Go ahead, use it. (Look at all those screws!).

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