ceiling load 5

[shades66]

could someone do a quick load calc on a 8ft x 11ft interior room, 2x4 wood construction, wall and ceiling joists at 16" o.c..
flat roof ceiling with 2 layers of 1/2" fire rated plywood . I need to get two men up there to install a transformer to adjacent block wall.
400#

 

[JedClampett]

No

 

[shades66]

thnx jed, I assume whomever built the room did calcs, moons ago, I was up there and it "seems" sturdy enough for anything you might want walking around, but I cant red the load capacity sign on the wall, it's been painted over, there is an access ladder by the sign. I figure two big guys carrying the xfrmr 400 # max. I can see the ceiling joists from inside the room

 

[bigmig]

Shore it up from below. It is the quickest and safest way to approach this.

 

[shades66]

I dont want to do anything, hopefully.. I feel it's plenty hefty for temp work to get the xfmr hung on the back wall of the building, xfmr will not be loading the roof, except while it sits there waiting to be installed, it's a small 80 lb xfmr.

 

[XR250]

If you feel it is plenty hefty, then why are you asking?

 

[shades66]

well Im thinking from what I can read thru the paint the old sign says 400# max capacity,not sure 100%... so I'm close and

 

[phamENG]

So it sounds like you need a Structural engineer. Hire one. We don't work for free.

 

[ChorasDen]

So you have 2x4 joists of unknown species possibly spanning 11ft and you wish to move a relatively large construction load (at least compared to the joists) across this system?

I agree with phamENG, best to consult with a local engineer experienced in wood design for something like this.

 

[MIStructE_IRE]

Say I, a stranger on the internet, told you it would all be OK, and it wasn’t, and one of your men fell to their death. What then? Go hire a local structural engineer.

 

[BridgeSmith]

My quick math says don't be under it when you send the guys up there, and don't send anyone you like up there to do the work. IOW, unless you want to get someone killed, get a structural engineer to evaluate it.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

Hehehehehe

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

-Dik

 

[dik]

Just curious to see how close this is...

What are the floor joists? 2x8, 2x10 or 2x12? and are they spanning the 8' or the 11' dimension? 2x4s don't even come close, even for the short span. Do you know what the species and grade of the lumber is? Do the two layers of plywood cover the floor? Do you know what the grade of the plywood is? Is there a GWB ceiling underneath? Do the 2x4 stud walls have a double top plate? and what are they supported on? Is the grade of the studs the same as the floor joists? There are a bunch of things needed for you to solve your problem.

As the guys above noted, you should seek out a real engineer as opposed to an internet one.

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

-Dik

 

[shades66]

The 2X4's are southern Pine, double top plate on the walls, this room is built on a concrete floor, GWB ceiling under the joists, and the 1/2" plywood is PT, the span is the 8ft lgnth supported on a 2x10 header anchored to a concrete wall
I have hired a structural Engineer to have calcs of record , this was built long ago, never meant to hold a load on the ceiling, but in the meantime I needed to get the XFMR up and running and just thought I would ask kindly for an opinion on having a couple of guys up there, and I guess I got what I asked for
thnx guys

 

[XR250]

Honestly, even if the numbers don't work out, 400 lbs does not seem like an issue for that roof.
The load will likely be spread out over multiple rafters and the plywood will act like a membrane.
I see much worse stuff attempted without a problem.

 

[dik]

The floor joists are 2x4@16, too? Spanning the 8' dimension and not the 11' dimension.

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

-Dik

 

[dik]

I'm not into residential construction very much, but would you include a LL of 20 or 25 psf in addition to the 400# transformer?

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

-Dik

 

[ChorasDen]

20psf roof live load at a 1.25 LDF is intended as a "construction load", so I would argue you could either design the members with this 20psf live load to justify the design, or you could use a rolling point load approach with the 400lbs provided in the OP to check bending, shear, reaction, etc. The distribution of this load would be up to the determination of whomever is performing the calc. Of course with that approach, you would have to stipulate that no other loading can be applied to the joists while the 400lb load is on the ceiling, unless accounted for in the design.

Or were you referring to a 20psf attic storage load?

 

[shades66]

Thank You ChorasDen and XR250, That's all I was really asking. I ran into a situation where I needed to get a couple of my guys up on a ceiling of a built in room to hang a XFMR overhead. I pulled back enough GB to see what they had for ceiling and wall joists, I climbed up with my 200 lb self walked around, then fired off a question in here.

Seems I will be more careful when I ask the forum, a touchy lot when it comes to calcs on the fly, and understandably.
If someone asked me if it was ok to do some electrical work without an licensed electrician I would hesitate to offer anything but safe sound advice, as you and XR250 did.
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