I am trying to make my cement slab flat to float engineered. The room is aprox. 28ft by 12ft. The floor has a slight hump in the center. To make it flat I would need to fill either one side of the room or the other with floor leveler? I think? This seem excessive. It is aprox a 1/4 inch to 3/8 inch hump within ten foot. Is this within the tolerance to float an engineered floor? Any and all advice on making cement slab flat aprreciated.

Just buy some self leveling concrete,follow the directions printed on the side of the bag,and use enough to get within tolerance. You needn't make a mirror. Just make it better. Sounds like you are already pretty close to tolerance.

Or you can visit this link for ideas..

http://www.hardwoodinstaller.com/hardwoodinstaller/gluedown-prep.htm

Question about grinding slab. My slab is high in the center. Apon closer inspection if I try to fill in one side of the floor with leveling compond, it appears that by the time I get to the wall it will be as thick as 1 inch +

Seems like I will spend a lot on compound to do this. So now I am wondering if it might be better to grind the hump down? How is this down? Where do you get the equipment to do it? Is it do able with precision?

Most rentall stores have circle buffers that can use grinding stones to take out the hump. It will be a little dusty, but usually easier than using a flash patch or leveler.

When I built the interior walls to the bath room and anchored the wall to the cement with red heads, I broke through the concrete in what seemed to be about 1 1/2 inchs.

A long story short this made my decision to start adding floor level to one side of the room as opposed to grinding down the center and possibly making the cement to thin.

I hope the floor leveler holds up, its as thick as an 1 to 1 1/4 inch on the deep end. It is slow going and the hardest thing to find is somthing that is ten to 12 feet long that holds a true straight edge and is not to bulky to manuever.

I was hoping to complete the edges along all the walls, then use a long straight edge guided on each side. The room is 11 1/2 foot wide so I need a straight edge about 11 ft long. Its quite a pain in the you know what.

Just a thought--If you complete the edges first, you could hold a staight line(string) across the room and get the height difference of the center of the room in several locations. then complete the center of the room, then a 6' level would be the true straight line for the rest?

Nails into the wall on each side accompanied with a string across the room at the level in which you want to reach. You wont see the holes later anyway!

Some people even nail or drill into the concrete for the same effect.

Hope that helps.

Aluminum angle bar. Long, straight, light weight. At Orchard Supply.