Is there any way to check if a floor is completely level without having any advanced tools?
I want to be sure that a bookcase would not need extra support

  • pick up a pack of shims at the hardware store. I always shim the front so I lean the book case over the trim and back against the wall (and then strap it to the wall, if you can). This also lets me put round things on the shelf without worrying if they're going to roll out on me – Joe Sep 7 '18 at 22:50

The common tool to do this is a level. One that is 4 feet long is better because it can check the floor over a wider area for flatness and level. You really only need to check the area where you intend to set the book shelf and not the whole room.

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A level like this would not be considered an advanced tool as they are rather simple devices. If you find the longer sized levels too expensive you can instead find cheap short ones that you can use on the top edge of a 4 foot long, straight and even pine board.

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If you want to avoid buying any tool at all you could consider the idea to use pine board like the above example but substitute the cheap level with a Smart Phone running an app that simulates the bubble style level. For example there are many apps like this in the Google Play store for Android phones. (Similar apps on iPhone at the iTunes store site).

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The smart phone apps require you to calibrate your phone on a known level surface. Some folks may consider this idea a gimmick but it may be just what you need for a quick and simple check. The quality and repeatability of the cell phone type of app can vary from app to app and be affected by the quality of sensors in the phone. So if you go this direction I encourage you to download three or four of the free apps and find the one that best suits your needs.

  • Is this tool easily found e.g. in any hardware store? – Jim Aug 5 '17 at 9:35
  • Well certainly in a big box store with a tool department. Most hardware stores sell tools too. – Michael Karas Aug 5 '17 at 9:37
  • About your update, somehow this seems like a chicken-egg problem. How would I know a surface in the house is already level to use it as a standard reference to calibrate the phone/app without using a tool? – Jim Aug 5 '17 at 9:58
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    You have to be creative. One way is to carry your phone into the tool department at Home Depot and just happen to calibrate it as you are looking at their better quality levels. – Michael Karas Aug 5 '17 at 10:07
  • @Jim : You can check if your surface is level even if the phone is mis-calibrated. Check for level four times, rotating the phone 90 degrees each time. If opposing directions are out of level to the same degree but in opposing directions, the surface is level, but the level isn't calibrated. – Joe Sep 8 '18 at 13:04

find a place you know to be level fill a jug or cup with water mark a line around jug showing where water is when level then take jug into room u want bookcase set it in a few spots around the area that if u dont want to spend 30$ for a cheap levle and more like 80$ for a good one

  • Would that work if I fill the cup fully? I mean why would I need to mark the jug? – Jim Aug 5 '17 at 13:19
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    Bigger (larger diameter) the better. A small cup may not show a slight out of level. – Lee Sam Aug 5 '17 at 17:59

Some "home inspectors" use a 1-inch marble or ball-bearing to see if it rolls, then may follow up with a 4-foot level for more accurate measurement of the slope.

  • Do they let it drop or how they place it on the floor? – Jim Aug 9 '17 at 17:28
  • What I have seen: Set on the floor, hold with single fingertip, then release so the finger doesn't urge the marble in any specific direction. – Upnorth Aug 10 '17 at 19:49

If you have a length of clear tubing, you can attach each end to a stick that you attach to some base so it's vertical.

Fill the tube with colored water until it's about 1/2 way up the stick, then mark the sticks where the water line is.

If you move the ends around, and find a place where the water level isn't at the line, it's not level.

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    This is roughly how the Egyptians did it. Works great over even and uneven surfaces. It's great for getting the right slope on your patio as well as checking bookcase level. – Wayfaring Stranger Sep 7 '18 at 23:43
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    I use this all the time, leveling a border around a room, grading part of my back yard and most recently leveling the beam to the ledger on a deck I just rebuilt. – Gary Bak Sep 8 '18 at 2:44

If your bookcase is perfectly square, you can use a plumb bob.

You can make a plumb bob out of a thin piece of string and any suitably heavy small object tied to the end. Once you've put the bookcase into position, suspend the weight to the left/right of it - the gap between the string and the bookcase should be the same distance all the way from top to bottom.

This method should only really be used where you need it to be approximately level, since you're essentially just eyeballing it with a little extra help. But it's quick and can be quickly assembled with stuff you should already have lying around the house.

If the bookcase is an irregular shape or wasn't assembled with perfect right angles between the base and sides then this method won't work.

  • Thanks for tip, but I am looking for a method to check before actually buying the bookcase – Jim Aug 9 '17 at 17:27

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