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How to Finish Concrete in Humid & Wet Weather

Drying concrete is more than the sun baking mud. Drying concrete is a chemical reaction that gives off heat and bleeds water. Concrete is finished to compact the surface, then finished a second time to make the surface shiny or rough after water in the concrete mix bleeds, or rises, to the surface and evaporates. Humidity is good for concrete. The longer concrete stays damp, the stronger it will eventually be. But uncured concrete should never be exposed to rain or hail. Even if the concrete seems to survive the storm, the surface will soon crumble to dust. You should never, under any circumstances, attempt to finish concrete in the rain.

Things You'll Need

  • Plastic sheeting
  • Bullfloat, screed or trowel for first finishing
  • Garden hose for excess bleed
  • Hand float or power float for second finishing
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    • 1

      Cover wet concrete with plastic sheeting when you are not finishing it. Nail or tack the plastic sheeting to the concrete forms. Forms are molds into which wet concrete is poured.

    • 2

      Bullfloat, screed or trowel wet concrete in all weather except precipitation. Bullfloats look like push brooms but substitute a plate for the broom. Screeds are boards pulled across the surface of wet concrete to compact, level and smooth the surface. Keep plastic sheeting within reach to immediately cover the concrete at the first drop of rain.

    • 3

      Check the pour hourly for excess bleed if weather permits. Excess water that pools on the surface of a fresh concrete slab can be pulled off by having two masons drag a garden hose across the surface of the slab.

    • 4

      Begin the second finishing of the poured concrete after all bleed water has disappeared. Apply the final finish to the concrete with either a bullfloat, hand float, power float or trowel. Interrupt the finishing and immediately cover the concrete with plastic if it begins to rain.

    • 5

      Edge and groove the concrete immediately after floating. Cover the concrete again with plastic sheeting for as long as rain appears likely. In humid, wet weather you may have to cover concrete for up to 28 days.