Method of installing a flooring system utilizing gypsum underlayments

1. A method of installing a flooring system comprising:

pouring a gypsum underlayment on a substrate;

allowing the underlayment to set, but not dry;

providing a water-borne sealer including a hardener, a hydrophobic epoxy resin and water; and

applying the sealer to the wet, but set underlayment, wherein the sealer partially seals the underlayment to promote permeation of water vapor through the sealer; and applying an adhesive to the gypsum underlayment less than 4 hours after the step of applying the sealer to the gypsum underlayment.

2. The method of claim 1 further comprising allowing the sealer to dry, providing a treated underlayment.

3. The method of claim 2 wherein the pH of the treated underlayment is about 9 or lower.

4. The method of claim 1 wherein the sealer is applied at a rate of about 400 ft 2 /gallon (37 m 2 /3.8 L).

5. The method of claim 1 wherein the gypsum underlayment is poured to a thickness between about 0.64 cm-about 1.9 cm.

6. The method of claim 1 further comprising applying a finished flooring to the adhesive.

7. The method of claim 6 wherein the finished flooring is at least one of a resilient flooring material, carpet and tile.

8. The method of claim 1 wherein the adhesive is water-based.

9. A method of installing a flooring system comprising: pouring a gypsum underlayment on a substrate; allowing the underlayment to set, but not dry; providing a water-borne sealing including a hardener, a hydrophobic epoxy resin and water; applying the sealer to the wet, but not set underlayment, wherein the sealer partially seals the underlayment to promote permeation of water vapor through the sealer; and applying an elastomeric water-proofing and crack-isolation membrane within 2-4 hours after the step of applying the sealer to the gypsum underlayment.