Does Armstrong have a product which can be used to level underlayment boards?
Armstrong S-184 Fast-Setting Patch & Underlayment with water or S-194 Patch & Underlayment with S-195 Latex can be used for overall leveling of approved suspended wood underlayments, but are not recommended over stripwood floors. Both are Portland-cement based with a compressive strength of 4,500 psi (pounds per square inch) and can also be used over concrete, ceramic tile, quarry tile, terrazzo, and existing asphalt adhesive residue. Once spread, it is dry and ready for flooring installation in about one hour.