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Phil, Mechanical Engineer
Category: Home Improvement
Satisfied Customers: 8439
Experience:  Retired contractor, 51 years experience
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Hello, Ive recently removed a basement floor slab. The guys

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I've recently removed a basement floor slab. The guys I hired to replace the concrete used very wet concrete and went in and power troweled while the concrete was still too wet/soft. There were ridges left and some wash boarding effect. I'm looking for solutions other then removing the entire floor again and re-pouring. In example floor sanding or re-topping the floor. Looking for options, Thanks Mike
Welcome to Just Answer Mike!

You have already mentioned two viable options... if the concrete has not fully set yet you might be able to rent a power floor sander and level the floor... if that fails you can pour another inch of concrete over it, ideally in controllable sections. so you can work from the existing floor while finishing the surface on the added inch.

If you use a floor sander wear a cartridge type floor mask and isolate the area from the rest of the house, cement dust is toxic.

Depending on how irregular the existing surface is, you can set floor tile in a thick grout.... leveling it as you go with a 6 foot straight edge. It will help to use a sander to remove the worst of the high spots.

Let me know what you think, we can go from there without any time limit as long as you rate my comments *positively.


Customer: replied 4 years ago.

Thanks Phil, Would the sander used be a belt type sander or an orbital type sander? Will it leave me with a smooth surface? The concrete is about 4 days old now. It was still slightly soft the day after. I thought most of the equipment used for concrete resurfacing was for set concrete.

If I considered resurfacing with a topping, would it be more of a self-leveling concrete or a regular type concrete?

Hello again, you would use a walk behind type 20 or 24 inch disc sander with the course grit paper.

It should leave a smooth surface, but that depends on how high the ridges are and how close to the surface the aggregate (rock) is.

it will be a trial and error approach.. nothing easy about it. We are not dealing with a standard sort of situation here so will not be going by any sort of finishing standards. Your concrete by the way is already *set... it is just not *cured*... it takes 30 days to cure. at 4 days it is about 60% as hard as it will eventually get, it will be easier to sand before it cures totally of course. Each day you wait will make it harder to sand.

Tell me how high the ridges are in the current surface please.

Use a self leveling topping not regular cement.

Stay in touch as needed by rating my responses so far *positively. I hold the question open for you in that case.


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