Level over a distance, Accuracy

[Dan Racette]

Distance:
I would like to a level a surface that is 8 feet long. How can I verify "level" over such a distance without a very long level? Can I use a short level in many spots?

Accuracy:

Working with an "out of square" square, can be rough. What about level accuracy? Besides another level. How do you check to see if your level is reading accurately? Any favorite brands/types?

Dan

[Robert Rozaieski]

1. To level over a long distance I would use a laser level (got one last x-mas). If you don't have one or don't want to aquire one you can get a line level for $2-3 from any home center. Just snap the line level onto some nylon mason's twine and you can mak any length level just by pulling the line taught. You can use a shorter level in several places (I have done this in a pinch) but with less accuracy.

2. To test a level, put it on a surface and draw a level line. Then turn the level 180 degrees (keep the top and bottom oriented the same and just switch the left and right) and put the same edge on the line you drew. The bubble should still read level if the level is accurate.

[Mike Henderson]

Some transparent tubing with water works very well. If the surface is flat, where you need to have the tubing on top of the surface, use a ruler and raise one end so that the water level is at a fixed level, like 12 inches. Then take the other end and measure from the water level to the surface. The measurement will give you the amount of grade. If the measurement is 11 inches, that end is one inch higher than the other end.

Cheap but effective. Guaranteed to be accurate.

Mike

[Brett Baldwin]

Depending on how accurate you need to be, an 8' piece of straight 2" angle iron could be set across the span. A level on the angle iron would set your reference and peaks and valleys in your surface could be measured from this reference. This would be essentially the same as the string method above but with a more stable reference.

[Dan Racette]

Definitely the water is an old and good method. Umm...no lasers allowed here! ;)

Is there a dry way?

[Robert Rozaieski]

You could make an 8' libella :D (basically an equilateral triangle with a plumb bob). Or you could make a smaller one and place in on a straight 8' board.

From the Aug-2006 Popular Woodworking:

"This still useful ancient tool was used by ancient Eyptians to build the pyramids and helped the Romans line up their roads and aquaducts. We show you how to build one for yourself out of scrap wood and brass."

http://www.popularwoodworking.com/images/article_index/0806Libella.jpg

[Jerry Palmer]

You could make an 8' libella :D (basically an equilateral triangle with a plumb bob). Or you could make a smaller one and place in on a straight 8' board.

From the Aug-2006 Popular Woodworking:

"This still useful ancient tool was used by ancient Eyptians to build the pyramids and helped the Romans line up their roads and aquaducts. We show you how to build one for yourself out of scrap wood and brass."

http://www.popularwoodworking.com/images/article_index/0806Libella.jpg

Speaking of Roman Aquaducts, it is amazing to me that in the First Century AD, the aquaducts feeding Rome provided more water per day than was available to New York City in 1986.

[Rolf Safferthal]

I´d like to recommend something different. Buy a long straightedge made from aluminum. These are cheap. Put it on the surface you like to check and look if you can see light shining through underneath.

Another possibility is to use feeler gauges to determine the distance between the straightedge and the surface. To check that the straightedge is level - put a level on top! Even a short one will work.