I have two questions.

First, what type of device are you guys using to measure flatness? I'm thinking I need a piece of 10' angle iron or something.

Second, I have had my subfloor leveled/flattened. However they are just not having any luck getting some of it flat. I have not had a chance to check it yet for how much out of flat it is (see question #1). What do you do in this case? I'll figure out and post my flatness within a day or two.

Thanks for your help,

Jeff

Edit: had to finish the second question.

You can use anything that's "straight as an arrow". I use my 6 foot straight edge. I know, I need 10 feet ! It's just all I've ever used, I can tell buy running it accross the slab.
Alot of guys will use their chalkline,( 1 end under a bucket of glue, and run the other end across the slab ).

I use a ¾"x5"x10' aluminum tile screed.

That would be a pain for me to carry, even though I have a longbed, ( no rack on top ).

I use a 10' piece of 1 1/2" galvanized pipe

I use a six footer like Perry's and is only 3" x 3/4. I find straight edges are a hassle only because they won't stand up by themslves.

But they come in handy for a trillion other things

So do I. It's easy to roll it around to find the uneven spots.

We have 6 ft. and 8 ft levels that expand to double their length, And they stand up on their own. Costly, but a one time expense.

Can't pipe get bent? How have you checked it?

I dont use pipe, but I imagine you can check it by rolling it .

the pipe is somewhat heavy guage so it would take a lot to bend it. I keep it lying flat in my box truck so it's pretty safe. And it does work well to just roll around to check different spots of the floor.

Looks like I'll take a trip to the home center tomorrow and see what I can come up with in the way of 10' sticks of pipe. I have access to an 8' level and I'm not opposed to purchasing one either however, I don't know how often I would use it.

I'll get something and figure out how out of flat the floor is and see if I can get any opinions on my second question in the original post.

Thanks,

Jeff

Second question: One thing is you just cant flatten a floor just by filling. Grinding or sanding the high spots is a must. Plus, you need to check flatness both directions, not just one direction.

I've used the string and bucket method before. But actually seeing where the string hits the high and low spots can be tricky to say the least. Best method is a laser IMHO. But then that takes more time than a level and is tricky just like the string. Strings need to be taunt and can sag over long distances. Then there is that other method of driving screws into the substrate to even heights and then screeding to the tops of the screws. Thats another story I am to tired to explain.

Having a level that is straight and rigid made with four sides that cannot get bent easily is the best one I have found to be true.

How do you use a pipe, to drag mud to fill the low spots?

My aluminum screed, has a dual purpose. Check the slab, and use it to fix the slab.