Measuring the grade of a patio

[Dick Adams]

What are some simple ways to measure the grade of my patio?

Without ranting and raving, I contract with a quality reputation company to put it in and they subcontracted it to a fly-by-night contractor who appears to use day laborers. I want the measurements in hand when I go after them.

One constraint is my wife will have to do all the bending because I have two slugs of concrete holding my spine together. Since she is not mechanically inclined, it needs to be as simple as possible and sill be accurate.

I did try the string method, but we had communication problems. Maybe I just need a neighbor to help me do it.

Constructive suggestions are always valued.

Dick

P.S.: alt.home.repairs is one of the ten best newsgroups on USENET. I like to believe misc.taxes.moderated (which I moderate) is in the same league.

[trader4]

Simplest/cheapest method is to use a string level. More accurate/expensive is to use a laser level.

[RicodJour]

Have any studies to back that up? ;)

The general idea is to elevate the level line so you won't have to bend over and use a tape measure or better yet a folding rule to measure down to the line. You'll be measuring down so the bigger dimension is at a lower elevation.

You can use a laser level on a tripod or set up on a patio table, a water level or use a line level on a string tied between two stakes driven into the ground. If you can't drive a stake at one end, say into the patio, you only need one end secured and you can swing the line, make sure it's level with the line level and take a reading.

If you're using this as ammunition, the more accurate the readings the better. The laser level and the water level would give equally accurate readings if used correctly. The line level would be the least accurate. A water level would be my recommendation.

What's the reason for needing the grade readings? Are you having drainage problems?

R

[cavedweller]

How about just using a 4' bubble level (after all, how big is your patio?). If it's level, there's no slope. If it slopes, shim the one end until it IS level. The thinkness of the shim, divided by 4, is the slope per foot. Check a few spots.

Who do you intend to go after? The prime contractor with the "quality reputation" should be more than willing to come out and verify the job his sub did...and in your presence.

[cavedweller]

Everybody knows what "thinkness" is, right?

[Nate Nagel]

Ayup. but you can get close enough to see if there's a problem with a string level. Just drive a small stake in the ground outside the deck and tie the string to it, pull it to the siding of the house, adjust until the bubble says level and measure height at house and edge of deck. the difference between the two measurements is your rise, I assume you already know the run.

good luck

nate

[Buck Turgidson]

One simple way is to take a 4' level and lay it on the patio. It should drop off about 1" for every 4 feet. If you stick a 1-by under the level, it should read level.

[Dick Adams]

Big time!

Dick

[Colbyt]

Dick,

Buck is right on this one. 1/4" per foot is considered a normal drainage factor. If you have problems a little more would not hurt if the width or run is less than 12'. Personally I like 1/2" slope per foot.

You set the four foot level on the slab or form. On the downhill side you place something that is 1" thick. If it reads level, the bubble on dead center, you have 1/4" slope per foot. To do the 1/2" slope you would use something 2" thick at the lower end.

A good compromise between the two measurements would be the level resting on the form and a 2x4 placed flat at the other end. If the level reads "level" you have about 3/8" drop per foot of run.

Colbyt

[HeyBub]

The easiest way is to put a protractor and level on the patio.

The next easiest way is to put a marble at the high end and time how long it takes to get to the other. Knowing the distance it traveled and the time it took, you can figure out the slope.

It's been a long time since I had to figure the cosine of anything...

[trader4]

IMO, 1/4 inch per foot slope is excessive and 1/2" per foot is a disaster, which will be obvious to the the eye. Normal practice is about 1/8" per foot, which is plenty for water to run off, which is all you need.

[cavedweller]

You got it.

Just curious why the OP needs all this when a garden hose applied to the patio in the presence of the contractor will make the point.

[Harry K]

Were it me, I would want to go into thie discussion armed with knowledge. As in "what is sthe exact slope" What is the required slope per the code (if it exists) or per good building practices (from the library or research on line).

Finding the slope is a simple few minute job using one of several cheap, fast methods.

Harry K

[cavedweller]

No question.

As in "what is sthe exact slope" What is the required

No question here either, except those things might have been done before giving the job to the "quality" (per the OP) contractor. Look, for instance, at the various opinions expressed as to what is the "correct" slope for what most seem to be assuming is a concrete patio.

Without doubt...but it doesn't alter the fact that I'm still curious.

[Wayne Whitney]

What about for a patio adjoining a house? 1/8" per foot is the "proper" slope for a patio, but building codes typically specify that around the foundation there should be a 6" drop over 10 feet, with an exception allowing 1/4" per foot where conditions warrant. So should a patio adjoining a house have a 1/4" per foot slope for the first ten feet away from the house?

Thanks, Wayne

[RicodJour]

There are some factors that will have major impact on the marble rolling and would make it an unreliable measurement. Any surface irregularity such as the joints between pavers, any dips in a poured concrete surface, the smoothness of the patio material, etc.

Short of doing tons of test there's no way you could find a reliable average number, and even if _you_ felt the test was reliable there's no way a contractor would accept playing with marbles as an acceptable indication of the slope. The OP also mentioned that they're trying to avoid bending over...

R

[RicodJour]

No. The slope of a permeable soil surface requires a greater slope. An impermeable patio surface does not.

R

[cavedweller]

...and unless I've missed something, we still don't know what the surface of the patio. I know the OP said he had concrete in his hips.

[cavedweller]

The missing "is". 8))

[Goedjn]

Or you can just pour water on it, and see if it runs off. What's a patio supposed to be? 1:50?