Polished Floor Slabs

[bigmig]

We have a client who wants to do a polished floor topping slab over a wood framed structural floor. The project is residential.
We have seen mixed results with this type of finish in the past. The biggest issue is that they all crack in spots that are not
control joint related, regardless of structural stiffness below.

We have also had issues with coloration, staining, the floor being too polished so it is slick as ice when wet.

I'm just wondering if anyone has experience with a project where it turned out great. What thickness of slab did you use?
Any tips or warnings or design guides?

Thank you.

 

[jayrod12]

The only times we've had success in these scenarios are where the topping is quite thick, 3" or thicker, has both a reinforcing grid/mesh (properly chaired to be top steel) and fibres. And has proper control joints installed. Otherwise it's just a whole mess of random cracking. The plywood ends up bonding with the concrete well, which ends up causing a whole bunch of restraint cracking. I'd recommend looking at intentionally debonding the topping to avoid the restraint cracking.

 

[EdStainless]

I knew someone who had a floor similar to this.
The framing was insane.
Compared to a normal floor it looked like solid wood.
And their floor wasn't highly polished but had a very fine honed finish.
There were some fine cracks, but they were very hard to see.
The biggest problem that they had was when someone spilled a glass of lemonade and it etched the surface of the floor.
At least with the honed finish it was slightly matt already, so it just bleached slightly.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[XR250]

I did this in my house with radiant tubing. Did not polish it though - used dye and epoxy covering.
Never had a single crack. 3 1/2" thick. Used 1" foam board between the slab and plywood. #4 @ 32" O.C. each way. Poured it in 2 days as a checker board so I could have real contraction joints. i.e formed out 20x20 sections with 2x4's +/- (depending on what made sense with the floor plan) and poured the areas on alternate days so the forms could be removed. The framing was basically 2x10 x 10 ft. @ 16" O.C.

 

[jhnblgr]

Use composite metal decking
Keep in mind thin concrete will crack easily and the grinding equipment vibrations might cause cracks. Type k cement might help with shrinkage cracks. Polish to 800 level and burnish.

 

[IceNine]

I did this for my house. 2" thick reinforced with W.W.R. (on bolsters), with rebar at reentrant corners and sawcut control joints. Put 6 mil poly on top of the plywood.
Used an integral color added at the batch plant, and had the floor polished. No cracks 14 years in.

 

[jerseyshore]

What rooms do you guys have an exposed concrete slab in your house?