SOPRASEAL LM 203 is a one-component spray applied non-permeable air barrier membrane used in wall construction. SOPRASEAL LM 203 is a water-based, ultra low VOC liquid product composed of a modified rubber formulation for elongation. This non-flammable, non-permeable air barrier provides moisture protection behind wall claddings such as brick, siding, metal panels, EIFS and stucco. Utilization of a slipsheet is required for stucco cladding.

Product Properties

  • Air Permeability ASTM ASTM E2178
  • Air Permeability ASTM ASTM E2357
  • Air Permeability ASTM ASTM E283


To apply SOPRASEAL LM 203 mix the product until thoroughly blended. Use a ¾” (19 mm) nap roller, paint brush or spray equipment to apply. Please refer to SOPREMA specifications and installation instructions for additional application guidelines prior to use.


Testing & Approvals

Related Products

DUOTACK® SPF Hose and Gun

The DUOTACK SPF Hose & Gun are used in conjunction with the DUOTACK SPF dual canister adhesive. A hose and…

View Product


Small — 24 pieces per box. Coverage per box 78.7 linear feet Large — 12 pieces per box. Coverage per…

View Product


SOPRA-ISO HD is a high density rigid polyisocyanurate panel designed for use as a cover board in approved multi-ply membrane…

View Product

Related Projects

Fourth Avenue Junior High School – Yuma, Arizona

The building that the Fourth Avenue Junior High resides in was built in 1920 and was named a National Historic Landmark in 1982. When the building required a re-cover roof project, its National Historic Landmark status and student safety was top priority. Due to its history and age, care needed to be taken when completing the project. The products installed were required to be odor-less and could not damage the building. A second requirement for the project was that it be completed quickly and without lingering odors, because they planned to complete the installation over their holiday break. This is where SOPREMA products came into play.

Cleveland Museum of Art – Cleveland, Ohio

This $350 million project was the largest cultural project in Ohio’s history. SOPREMA’s SOPRALENE® Flam 180 polymer modified bitumen two-ply system was installed. SOPREMA was the ideal manufacturer for the project as they were able to provide a variety of quality products to accommodate the projects’
needs with a single source warranty.