Leveled Ceiling, Uneven Measurements - What's Wrong Here?

[Element13]

TL;DR Summary

Level reads leveled but the measurements are off by almost a 1/4 inch

Hi All,

I received good insight from a previous post, https://www.physicsforums.com/threads/pulling-a-heavy-load.1015640/#post-6637181, now that I'm at the point of expanding the drawer support on the ceiling, I ran into the following.

How is it that my level says it's leveled but the tape measure tells me that the distance from the ceiling to the board's left corner is off, by about a 1/4 of an inch, from the right corner of the board; and in-case you're wondering, the ceiling is also leveled.

Any ideas as to why or what I'm doing wrong or missing here?

FYI, the string you see in the "center measurement - ceiling to board" photo is to align and mark the center point to the ceiling, where I'll be attaching the hardware to support the drawer's extension. I placed a string on the other two measurement photos, as well, so I could get as leveled a reading as possible; overkill perhaps, but every fraction counts.

Peace,
Element13

 

[jack action]

What do you know about the sensitivity of your level? And what about the precision of your reading?

For example, this level sensitivity is 0.133 in/ft - 38min/0.1in. This means that the bubble would move 0.1" for an angle of 38min (0.633°). For a 26" distance between 2 points, it would correspond to a 0.288" difference.

From what I understand, the human eye cannot see a 0.02" (0.5mm) movement of the bubble, which corresponds to a 0.058" difference over a 26" length (with the level presented, that is).

 

[Lnewqban]

I would use a transparent hose filled with water to verify what is level and what is not.

Please, see:
https://www.wikihow.com/Use-a-Water-Level

 

[Baluncore]

Summary: Level reads leveled but the measurements are off by almost a 1/4 inch

Any ideas as to why or what I'm doing wrong or missing here?

If you reversed your level between the two measurements, you will see twice the error in the instrument.

Check the instrument by setting it on two knife edges to read zero, then reverse the instrument and read the error. If adjustable, split the difference and repeat.

 

[Element13]

What do you know about the sensitivity of your level? And what about the precision of your reading?

For example, this level sensitivity is 0.133 in/ft - 38min/0.1in. This means that the bubble would move 0.1" for an angle of 38min (0.633°). For a 26" distance between 2 points, it would correspond to a 0.288" difference.

From what I understand, the human eye cannot see a 0.02" (0.5mm) movement of the bubble, which corresponds to a 0.058" difference over a 26" length (with the level presented, that is).

jack action,

Thank you for that education, I honestly didn't know that I needed to check for that, nor would I have considered it. After reading your reply I thought it was time for an upgrade to digital but it turns out they're not exempt from sensitivity either (https://www.finehomebuilding.com/2013/03/07/digital-levels-is-a-brain-better-than-a-bubble), however they do offer a few perks one being a digital readout.

Peace,
Element13

 

[Element13]

I would use a transparent hose filled with water to verify what is level and what is not.

Please, see:
https://www.wikihow.com/Use-a-Water-Level

Lnewqban,

I didn't think of that, thanks. I actually learned to use them when I was in my twenties and installing drop ceilings.

Peace,
Element13

 

[Element13]

If you reversed your level between the two measurements, you will see twice the error in the instrument.

Check the instrument by setting it on two knife edges to read zero, then reverse the instrument and read the error. If adjustable, split the difference and repeat.

Baluncore,

Thanks, I did reversed it and even flipped it but it still gave me the same reading. Unfortunately mine is not adjustable, it's a Stanley level I've had for 20tewnty some odd years.

What puzzles me, and I should have mentioned this in my reply to jack action, even allowing for the tools sensitivity, if I'm reading level at the start of the drawer extension, left and right measurements from the ceiling are at 16 inches, it stands to reason (my reasoning) that it would also be level, at 16 inches from the ceiling, at the end of the drawer extension as well.

Peace,
Element13

 

[Lnewqban]

Lnewqban,

I didn't think of that, thanks. I actually learned to use them when I was in my twenties and installing drop ceilings.

Peace,
Element13

In my practical experience, bubble levels are rustic tools, only good for rough estimates of spatial orientation.
Same applies to taking building surfaces as reference.
Therefore, my recommendation: Plumb, and water hose..., and tape measure, nothing else.

Important things that I would consider instead, regarding the two metal angles forming the drawer extensions:

* Smooth transition between wood surface of the shelf and each of the angles. I would even bend out the top flanges a little to "encourage" the drawer to enter the extension.

* Parallelism of the angles respect to each other and to the edges of the wood surface of the shelf: cross and diagonal measurements with tape.

* Flatness of the plane contained within both angles: Both angles should be as perfectly horizontal as possible in both ways, longitudinally and transversally along their entire length.

* Rigidity of each angle: I would hang any weight equivalent to about 1/4 of the estimated total weight of the loaded drawer from several points of the rolling surface along the supported and leveled angle. Would measure any deformation (longitudinal bending and transversal twisting), evaluate how it would impact the smooth rolling of the loaded drawer and the push-in/pull-out force, correct as needed with extra bracing.

* Resistance to any longitudinal displacement induced by the pulling-pushing force against the natural rolling resistance of the wells. Install appropriate bracing against ceiling and close to shelf as needed.

 

[Element13]

In my practical experience, bubble levels are rustic tools, only good for rough estimates of spatial orientation.
Same applies to taking building surfaces as reference.
Therefore, my recommendation: Plumb, and water hose..., and tape measure, nothing else.

Important things that I would consider instead, regarding the two metal angles forming the drawer extensions:

* Smooth transition between wood surface of the shelf and each of the angles. I would even bend out the top flanges a little to "encourage" the drawer to enter the extension.

* Parallelism of the angles respect to each other and to the edges of the wood surface of the shelf: cross and diagonal measurements with tape.

* Flatness of the plane contained within both angles: Both angles should be as perfectly horizontal as possible in both ways, longitudinally and transversally along their entire length.

* Rigidity of each angle: I would hang any weight equivalent to about 1/4 of the estimated total weight of the loaded drawer from several points of the rolling surface along the supported and leveled angle. Would measure any deformation (longitudinal bending and transversal twisting), evaluate how it would impact the smooth rolling of the loaded drawer and the push-in/pull-out force, correct as needed with extra bracing.

* Resistance to any longitudinal displacement induced by the pulling-pushing force against the natural rolling resistance of the wells. Install appropriate bracing against ceiling and close to shelf as needed.

Lnewqban,

Thank you for the info, I appreciate it.

* Smooth transition between wood surface...
I do have a transition happening at the joint, where the lip of the drawer ends and the drawer extension begins, and the angles are pushed out and secured into the wood/PVC that creates the channel for the drawer, about a 1/16 of an inch to avoid any friction or snags.

* Parallelism of the angles respect to each other...
They are of equal distance, parallel to each other.

* Flatness of the plane contained within both angles... and * Rigidity of each angle...
I plan to add horizontal support along the bottom of the extension, beginning at the joint, where I'll be adding shelf-like brackets, and then every 18 inches or so until the end of the extension. And yes, vertical support along the side and length of the angles as needed as well.

* Resistance to any longitudinal displacement...
I'm also securing the end of the extension to the ceiling joists with metal slotted angles, fastened in a triangular shape, the same slotted angle material I'll use for the vertical support.

And finally, I'll be adding a 1/4" thick piece of plywood, I believe it's called Luan, which I had a couple of 8'x4' sheets left over from a previous project, for the drawer wheels to ride on the length and width of the extension; which should also help secure and steady the angles.
Of course, if the Luan turns out not to be strong enough I'll go with 1/2 inch ply instead.

Oh, and I'll be adding PVC 1"x2" strips along the inside edge of the angles to help keep the drawer from moving to far left or right, keep it steady on its path.

I think I noted everything?

Again, thank you.

Peace,
Element13

 

[Jodo]

I would use a transparent hose filled with water to verify what is level and what is not.

Please, see:
https://www.wikihow.com/Use-a-Water-Level

I have a 250 foot length of clear 3/8 gas hose filled with a 50/50 mix of antifreeze/water (don't completely fill hose).
The green color helps visibility when using outside. The antifreeze stops the hose from cracking in the winter (cold here).
Couldn't ask for a more accurate level. I use it a lot for the starter strip on siding jobs.
Great advice Lnewqban.