FloorMuffler UltraSeal Underlayment – Premium Sound & Moisture Protection When the job calls for the quietest floor and a sealed moisture barrier, this is the underlayment pros spec by name. FloorMuffler UltraSeal is a premium cross-linked polypropylene (XLPP) foam underlayment with some of the highest acoustic ratings available — up to 74 dB IIC, 73 dB STC, and a 25 dB Delta IIC — under laminate, engineered hardwood, and solid hardwood floors. Pass the Sound Test Condos, apartments, and HOAs often require flooring assemblies to meet minimum IIC/STC ratings. UltraSeal's ratings clear the strictest building requirements, making it the go-to choice for multi-family projects, upper floors, and anywhere footstep noise is a dealbreaker. If a board needs to approve your floor, this is the spec sheet you want attached. Sealed Seams, Continuous Moisture Barrier The signature UltraSeal lip-and-tape system is built into every roll: each row overlaps and self-seals to the next, creating one continuous moisture barrier across the entire floor — no separate vapor film, no taping every seam by hand. Over concrete slabs, that sealed barrier is what protects your floor's locking system and your warranty. Premium Foam That Holds Up XLPP foam delivers superior compression resistance, supporting the tongue-and-groove locking system of floating floors so joints stay tight for the life of the floor. At 2mm, it smooths minor subfloor imperfections and adds cushion underfoot without the sponginess that damages click-lock joints. Versatile Across Installs Use it under floating laminate, floating or nail-down engineered hardwood, and nail-down solid hardwood, over concrete or wood subfloors. Compatible with electric and hydronic radiant heat. Where it works best: Condos, apartments, and multi-family projects with sound requirements Floating laminate and engineered hardwood floors Nail-down solid and engineered hardwood Concrete slabs and basements needing a sealed moisture barrier Radiant heat installations Not for use with: flooring that has a pre-attached pad. Backed by FloorMuffler's limited lifetime residential warranty and 10-year commercial warranty.
