Fix for Cut Truss Web Members 2

[Simba13]

Morning All,

I wanted a second opinion on how to approach repairing some cut roof truss web members. See the attached photos above (I wish I had gotten a few better pictures but you can get the gist), web members of three roof trusses (24" O.C.) were cut to make room for a little alcove in the master bath for a washer-dryer set. We've been asked to design repair modifications for this and other modifications done to the house. I'm not looking for specifics here, more of a high level approach of how to go about fixing this. I've thought about sistering larger members to convert it into a rafter roof in just this region or building a frame around the cut region to distribute the load (somehow...). I'm curious if any of you have seen this before from crazy DIYers and how you approached the design.

Thanks,

 

[oldestguy]

I suspect the verticals can take a significant part of the load so the new diagonals should put quite a lot of their load into the verticals, meaning the exact alignment of he diagonals does not have to match the old. Thus lay the new on top (side) of the joint. The connection might be either nails of screws with at least matching the grip from the plates there, which doesn't appear to be much. Before attaching coat the joint surfaces with glue.

 

[jayrod12]

I assume they also cut the bottom chords when cutting the webs. I'm impressed this thing is still standing. Something about wood and it's ability to redistribute loading continues to amaze me.

I'd be tempted to also provide beams on either side of the pop-up area to allow you to adequately support the ceiling in this area as well. If you're going to rafters, you're going to need to address the lateral component since there won't be a ridge beam. and if the bottom chords are cut, there goes the tension tie unless you're looking at the ceiling drywall acting like a sub-diaphragm.

 

[CrabbyT]

My coworker once told me that his step-grandpa liked to spend a lot of time in the attic, and no one knew why. After he passed away, his grandma's roof was starting to sag. Him and his dad went over to investigate, and it turns out the guy was storing a YUUUUUGE amount of adult magazines in the roof of his house. He had so much literature that he cut the diagonals out of the trusses to make room. Apparently he'd realized he'd gone too far, and they found several boxes of industrial sized hot glue sticks. I guess he'd tried to repair the trusses with hot glue because hammers and nails would've raised suspicions from his wife. The collection couldn't be compromised... I laughed so hard.

 

[KootK]

When I was a kid, there was a small, removable drywall panel thing in the ceiling of my bedroom, maybe 12" x 12". It was a great hiding spot for things right up until the season changed and it turned out that hatch was where my dad had to go to shut off the exterior water supply to keep the pipes from freezing. I was standing right beside my dad when it happened. I'd completely forgotten what I'd hid up there until it came tumbling out all over my dad's face. Damn internet kids don't know how good they've got it.

 

[KootK]

I could certainly get behind rafters to deal with any roof / top chord problems. You can probably just scab them on to the cut trusses and use the truss bottom chords resolve any thrust. This may well still leave you with ceiling / bottom chord problems however. See below for a conversation starter, reinforcement option.

 

[Simba13]

oldestguy I'm not sure I'm visualizing the connection of the new diagonals you're proposing properly, are you saying to attach new diagonals, albeit at a different angle right at the location of the existing plate of the cut diagonal? If so are you nailing or screwing through the plate? I could definitely roll with new diagonals at different angles, just not sure on the connection. FYI on this point, the guy installed new floor joists in this area for the washer to sit on. I'm going to need to go back with additional drywall cut to see how... but it was attached or sitting on the steel beam in the garage, my point being, that the diagonals could potentially be attached to those joists (they're 2x12s) maybe not a good solution but I thought I would mention that they're there.

jayrod12 As I'm getting into this I'm realizing that I'm going to need to go back to the house to take some extra measurements (not just for this issue) and I'll take a look at the bottom chord, I'll admit my human weakness on this one, I went in early September and that attic felt like it was about 110 degrees so I didn't notice whether the bottom chord was cut or not, even this guy wouldn't be that crazy I would hope... As for the lateral component, would I be able to rely on the attachment of the existing trusses to the plywood sheathing for this? since I would be sistering to the existing trusses which should be adequately fastened to the sheathing.

CrabbyT That's beyond hilarious... I would've liked to have been there to see the look on his wife's face

KootK That's actually the first time I've seen the term scabbing, looked it up, where exactly would I be scabbing? Yeah, your picture (first one) was kind of what I was thinking when I mentioned a frame. As an initial concept I think it's a reasonable way to just basically bypass those cut trusses as long as there is adequate reinforcement on either side.

 

[dik]

KootK... I think the right track, I'd think, but I'd move the LVLs to the inside of the intact trusses to make connections easier and to reduce the loading on the intact trusses. If the bottom chords have been removed, this can be accommodated by LVLs, maybe oriented horizontally along with vertical members.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[KootK]

...where exactly would I be scabbing?

You'd be nailing the rafters on to the sides of the existing top chords with the intent of:

1) indirectly connecting your rafters to the roof sheathing to brace them.

2) using the existing trusses kind of like scaffolding to ease erection.

3) mobilizing the truss bottom chord to help resolve rafter thrust.

How about sistering? Like that better?

KootK... I think the right track, I'd think, but I'd move the LVLs to the inside of the intact trusses to make connections easier and to reduce the loading on the intact trusses.

I disagree as far as my intent goes. I envision the LVL being taller than the bottom chords and the distribution members running though the trusses and landing on top of the LVL. So connections wouldn't be a problem. Also, I think that it will be easier to slip the LVL into empty truss spaces outside the void rather than along side the washer and drier inside the void. My intent is for the intact trusses to also be supported by the LVL's.

 

[Simba13]

KootK Yessir, I believe we're on the same page.

I wanted to think this through a bit before I went back so I know what to look for (as an example I was dumb enough to just take the bottom chord for granted). There is enough going on in this house that I might harang my boss into coming with me when I go back.

Thanks for all of your input, I feel like I know where to go from here.

 

[dik]

I guess we have a difference of opinion... the LVLs should be on the inside, even though it may be difficult to place them because they can be used to 'fix' the damage caused without interfering with the existing framing. The LVLs being taller will have no impact on anything other than making connections for the other LVL members easier.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[r13]

Will this works.

 

[KootK]

I guess we have a difference of opinion... the LVLs should be on the inside, even though it may be difficult to place them because they can be used to 'fix' the damage caused without interfering with the existing framing. The LVLs being taller will have no impact on anything other than making connections for the other LVL members easier.

No, you must be thinking of a different scheme than I am. Mine is shown below.

 

[Simba13]

r13 I like that idea too... Hmmm, I'll mull this over.

KootK That was a bit different than what I was imagining, it feels like in the sketch, that 2x4 vertical is still the main element that's keeping the roof from sagging...

 

[r13]

I think there are many ways to strengthen the opening, and associated members. Here is one.

 

[KootK]

it feels like in the sketch, that 2x4 vertical is still the main element that's keeping the roof from sagging...

Sure. The LVL hold up the distribution member, the distribution member holds up the 2x4 verticals, the 2x4 verticals hold up the truss en-macro. That's precisely what I'm proposing and I view it as minimally invasive if the numbers work. If the numbers don't work, then I might resort to installing the LVL and distribution members at the ceiling level, cutting out stuff in between and reframing as necessary. In that case, I would put the LVL's on the inside.

 

[dik]

Understood... thanks

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Simba13]

What about something like this at each of the three cut trusses (just brainstorming)

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1605735596/tips/Repair_Design_Concept_ktwjri.pdf[/url]

 

[KootK]

Sure, if the 2x12 can span on it's own, carrying the truss, that would be great. You wouldn't even need the vertical stiffeners.

What kind of span are we talking about for the truss?

 

[Simba13]

The full span of the bottom chord? Or just the span of those additional 2"x12"s? If the former, the house is around 30' wide, the area with the cut trusses and 2x12s is only around 8' or so. But wouldn't you still need some kind of vertical member to compensate for the missing diagonal? Or else the roof is going to sag, or am I missing something? The 2x12 is only on the bottom chord (or adjacent to) that's not really doing much aside from distributing the load of the washer-dryer.