hole in ceiling for hoist (attic truss above)

[gastgarage]

So I've asked a few questions of this forum over the years, and thought I'd provide a design answer I got from an engineer. This has been dealt with numerous times on GJ...

The question is what modifications need to be made to safely cut a 3' x 4' hole in the ceiling of a garage with attic trusses on the second floor, and the answer is as attached. Feels like a bit of overkill to me, and I may get a second opinion before proceeding, but here it is. There is more to the drawing, including a ridge board installation. The garage in question is a stick-built 26x34 footprint building with 2x6 framing.

By the time the garage was finished, the house/garage builder was no longer talking with us much (long story involving COVID). If it had been otherwise, there would have been several things I'd have been happy to pay for upfront, instead of doing structural modifications like this after the fact.

The hole will accommodate a hoist which will be supported by a steel framework attached to the building but essentially free-standing.

 

[Junkman]

Looks like a well-thought-out plan that will not be that difficult to execute. Sure you probably could get by with less, but the engineer isn't going to go out on a limb not knowing the weight that you will be lifting. A gantry crane might be a better choice if this is for pulling engines, etc.

 

[matt_i]

It seems like a detail of the roof is missing (?)

IOW, that's a detail of the floor and how they intend to design the opening into the floor.

If you think of the assembly, at least 1 truss would be "cut" by that opening on a typical 24" o-c truss array.

However there are also roof details which need to be spec'd. My guess is it would be 2x (?? = same size as top chord, likely a "6" or "8") crossmembers (perpendicular to typical trusses) which are also supported by joist hangers on both sides.

Very common is to envision the opening overlaid onto a 24" o-c truss array and then spread the trusses into a multi-ply "gang" just like the multi-ply LVL "gangs" they have designed for the floor. In this case above I would think two sets of double-ply trusses would be needed on each side of the opening.

Also along those lines it wouldn't be much more of a stretch to get nearly a 4'0" opening where 3'0" is spec'd. The typical space of 48" centers - 1-1/2" = 46-1/2" would be further shortened by two more truss plies of 1-1/2" meaning 43-1/2" rough opening.

It also might save buying the triple ply LVLs as the bottom chords would be actively involved instead...just a thought.

If the building is already finished then this advice is all mostly useless. But in that case I have to ask how you are going to feed (guessing here) 32' long LVL beams across the top of the walls - I think you have to open up the roof and remove sheathing...not un-doable but quite a pain.

 

[BillK]

Exactly where is the "hoist" going to be located and supported ?

 

[The Cobbler]

It seems like a detail of the roof is missing (?)
....

thr bottom line reads "not included for clarity"

 

[matt_i]

Correct but those are trusses which are existing in the "white space" that they don't detail because it would just make the drawing "busy" and harder to read and they don't contribute functionally to the hole thru the floor.

 

[The Cobbler]

they are attic trusses so there would probably not be any webs cut out in that area , so the roof would still be supported the same ?

 

[jmarkwolf]

Why not locate your hoist over the stairs to the attic, with provision to roll loads from "space" to the upstairs floor? That way you won't have to compromise the upstairs deck with a 3x4 foot hole, and you won't lose any floor space.

That's what I plane to do in my 2-story shop.

 

[gastgarage]

Thanks for all the replies!

Junkman -- hoist is mainly intended to get stuff up to the attic storage that is either too heavy and/or bulky to carry up the stairs easily (especially as my back and I get older...)

matt_i -- The roof details are included elsewhere on the engineered drawings. I may indeed go to a 3.5 x 4' opening or maybe even 4x4'.

The building is unfortunately completely finished; I've thought about how to get the LVLs up to the attic. There's a window on the front gable, will probably bring LVLs in that way if they can be physically then moved into the ceiling space adjacent to the existing trusses. If that's not physically possible then will have to remove roof shingles and sheathing. Either way it'll involve a Lull or similar machine.

BillK -- The hoist will be above the new hole, supported by a steel framework sufficient to carry the load and attached to the building.

Cobbler -- because the bottom chord is cut, the overall load-carrying capacity of the attic truss is altered. Hence the need for all the modifications, including sistering to the rafter part of the trusses which is included in the engineer's recommendations.

jmarkwolf -- the only suitable place in line with the stairs for a hole in the ceiling would be the landing at the top of the stairs (approx where the caption "new 2-2x10 header" is on the drawing), which could theoretically be done. However, there's not enough headroom to bring any tall loads into that space, and more importantly there's a bathroom on the main floor underneath.

 

[BillK]

Ok, so what is the heaviest item you ever envision putting up there ?

 

[gastgarage]

I believe the spec for the attic trusses is that it'll carry 40lbs/sq ft, so will stay within that limit. The hoist will lift 1000 lbs; probably any one item in the attic would be no heavier than 750lbs.

 

[BillK]

Wow, Thats a lot of weight. I guess you need the "over engineering" Complete engines ?

 

[gastgarage]

I do have one engine on a run stand that needs to go upstairs. The other single heaviest items would be a smaller South Bend lathe that may go upstairs and a scroll compressor that will. Everything else heavy are tools that'll go on the main floor.

 

[firebirdparts]

The floor honestly is not very interesting . What would be interesting is what is holding the roof up.

If you're wondering why those long LVL's are on 8" centers or doubled, it's because the rest of the structure is 9-1/4" tall and they can only be that tall without messing everything up. Steel would be a reasonable alternative there, but I guess it's mostly about whatever is cheapest. Having them be taller and hang down into the space below would be also reasonable. having them taller and sticking up into the space above would be weird.

 

[Innovate1]

BillK -- The hoist will be above the new hole, supported by a steel framework sufficient to carry the load and attached to the building.

Where is it attached to the building?
Big difference if it is supported by the ceiling(upper floor) or goes down to the lower floor.

What holds up the peak of the roof at the trusses that were cut for the opening? Is that part of the steel structure?

The drawing you posted is only part of the whole structure and hard to tell without the other details. You mentioned adding a ridge board/beam. What supports that?

Is the upper level storage only in the area where added floor joists are shown? Seems like truss webs would make moving things in the attic difficult.

 

[manwithtools]

Is the upper level storage only in the area where added floor joists are shown? Seems like truss webs would make moving things in the attic difficult.

See the post title - Attic Truss =