Solid Hardwood, Engineered and Laminate Flooring - Best way to measure flatness of concrete

What is the best/easiest way to measure the flatness of my concrete slab? I know I need a straight edge to measure from, but I've read about using a 2X4, a more expensive piece of straight lumber, steel pipe (would PVC be staraight enough?), string (exactly how?), a laser (mounted on a stand; set on the floor?), etc. Opnions? Thanks.

String and PVC would not work because they are not rigid enough. A 2x4 is risky because finding one that is straight enough may be difficult. If you want to spend the money on a rental, then go the laser route, but if you can find a long piece of aluminum (similar to a 1x4), then this would probably be the cheapest and easiest. I guess a big factor which determine your choice your the distance you need to measure...might be hard to find a stright edge like 15-20 long.

If you set something heavy on the end of the string and then pull it out and stretch it tight, a string can work. Just don't let it bridge a high spot.


I like my 10' long aluminum screed Basically is an aluminum 1x6. I also use it to drag floor prep mud, across the low spots as a big trowel. Don't use wood for this as it will start bowing as soon as it hits the moisture from the mud.

The first 2 pulls my be ok, but anymore and get a new board that is straight.

Where could I get one of these aluminum 2x4s?

Flooring supply house in the yellow pages. They're hard to find.

Ceramic tile distributors will have them in stock.