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-   -   concrete ceiling joist(beams) (http://www.diychatroom.com/f19/concrete-ceiling-joist-beams-93144/)

stacey2345 01-22-2011 04:35 PM

concrete ceiling joist(beams)
 
I live in an old NYC apartment building it has concrete ceilings i want to find the joists in it (if it has any) so i can install heavy boxing bag.i drilled a hole in the center of the room next to the light thinking the beam would be there but the drill went trough the concrete past it and no beam just empty space beneath the concrete ceiling.My question is does old apartment buildings have wooden beams in their ceilings beneath the concrete?
so i know to get a stud finer to try to detect it..

concretemasonry 01-22-2011 08:00 PM

You may not have any wood beams.

Most codes prohibit wood to support a more permanent and rigid material like poured concrete.

You could have any number of structural configurations and materials. Just because a lightweight electrical fixture is there, it does not mean it is supported by a real structural element.

check with neighbors since they may have already done the detective work.

gregzoll 01-22-2011 09:25 PM

What made you think that there is wood joists in a concrete building? The floors would have rebar in them, or steel skins that the would have poured the floor on if they did not use wood planks to support the concrete when they poured the floors. I want to see a picture of this hole that you punched through a ceiling. BTW, how old is this building?

stacey2345 01-23-2011 04:52 AM

I wasn't sure if i have beams i thought i wasn't sure if have anything solid up there.
i made small hole with a 4''-5'' long screw so the picture wont show anything inside the hole its not wide enough as i said i hit concrete past the seiling(drywall) and empty space after that.
so its pointless to buy stud finder to try to find anything solid in the sealing?
Could i have any solid steel bars up there?
in the same building but different apartment i had big ceiling fan in the dining room so i assumed it was attached on something solid but i dont really know.
the building was build 1923 its 6 floors ap buildings in Queens NY.

gregzoll 01-23-2011 07:56 AM

If in the old factory or warehouse district, most likely built with steel & concrete. Would like to see a picture of the outside, since NYC has a lot of unique architecture.

Ron6519 01-23-2011 08:52 AM

Quote:

Originally Posted by stacey2345 (Post 575774)
I live in an old NYC apartment building it has concrete ceilings i want to find the joists in it (if it has any) so i can install heavy boxing bag.i drilled a hole in the center of the room next to the light thinking the beam would be there but the drill went trough the concrete past it and no beam just empty space beneath the concrete ceiling.My question is does old apartment buildings have wooden beams in their ceilings beneath the concrete?
so i know to get a stud finer to try to detect it..

You don't live in a concrete building. You live in a traditionally wood framed structure with a 3 coat plaster wall. What you think is concrete is the base plaster coat.
You can use a stud finder or you can find the joists by knocking on the ceiling. Where the framing is will be a higher piched sound. Between the studs a lower piched sound. To get the exact location, use a 1/8" masonary bit. The plaster will be 1/2" 3/4" thick. If the bit goes in that far and doesn't go through , you hit the wood beam. Go to the left and right until the bit goes all the way through. That's the width of the beam.
Put the lag bolt in the middle of the beam.
Be aware that the bags vibration will transmit to the floor above and they will feel it.
Ron

stacey2345 01-23-2011 11:49 PM

thx Ron

i will use stud finder to find the beams and then i will prob drill to make sure i find the middle of it.
changed my mind about the boxing back because the vibration will bother the neighbors but i will hang a swing.
U think those beams are solid enough to hold about 120 lbs?is it better if i put the swing closer to the wall?

Ron6519 01-24-2011 07:31 AM

Quote:

Originally Posted by stacey2345 (Post 576685)
thx Ron

i will use stud finder to find the beams and then i will prob drill to make sure i find the middle of it.
changed my mind about the boxing back because the vibration will bother the neighbors but i will hang a swing.
U think those beams are solid enough to hold about 120 lbs?is it better if i put the swing closer to the wall?

The swing with the load might flex the joist and crack the plaster. A 120 lb. static load is much greater when it's in motion.
Ron

Daniel Holzman 01-24-2011 07:57 AM

Indeed, you live in an apartment, so I am guessing you do not own the building. A swing exerts torsional forces on the beam due to line of action of the chain not passing through the centroid of the beam when you are not perfectly plumb. Additionally, as noted by another poster, the force on the chain is greater than static load due to centripetal acceleration. The force is greatest when you are at the low point of the arc.

This combination of forces may have unfortunate consequences for the beam and the plaster, and might be a bad plan if you do not have permission to alter the apartment.

itsreallyconc 01-24-2011 12:46 PM

a ' bad plan ' means either the ceiling OR the building above you can fall down :yes:

stacey2345 01-24-2011 01:13 PM

Well im not going to be swinging it with a big arc like the the kids at the park most of the time the force would be plumb u know just hanging straight down on it.it may be a little shacking involved but lots of swinging..
But i certainly dont want to crack the plaster so if there is any possibility of that happening i wont do it..

Tnx

SteelToes 01-24-2011 01:51 PM

Quote:

Originally Posted by stacey2345 (Post 576943)
Well im not going to be swinging it with a big arc like the the kids at the park most of the time the force would be plumb u know just hanging straight down on it.it may be a little shacking involved but lots of swinging..
But i certainly dont want to crack the plaster so if there is any possibility of that happening i wont do it..

Tnx

Keep swinging hard and they will not complain...:hang:,
Or just build one of these stands that can go against the exterior wall ...

itsreallyconc 01-24-2011 04:07 PM

using ' torsional forces ', ' centroid of the beam ', & ' centripetal acceleration ' all in the same sentence will probably cause chris matthews to have another thrill running up his leg :laughing:


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