Rmax® Below Grade
insulation & protection board

Rmax® Below Grade is an energy-efficient thermal insulation and protection board composed of a polyisocyanurate (polyiso) foam core bonded to reinforced polymeric facers on each side. Polyiso’s closed-cell and closed matrix foam core, along with its durable facers, create a multi-layered defense against water absorption and protection during backfill, making it a great choice for below-grade applications.

Construction Applications

- Below-grade exterior walls
- Blind side walls
- Under slab
- Slab on grade

Why Rmax® Below Grade?

Durable Facer, Added Protection
Rmax® Below Grade has a high-strength, water-shedding facer for added foundation protection.

Achieves Thermal Performance
Higher R-value per inch compared to XPS & other insulation. Rmax® Below Grade meets requirements with a thinner profile.

Resists Water Absorption
The closed-cell & closed matrix of Rmax® Below Grade foam board meets water absorption requirements, with less than 0.3% absorption.

High Compressive Strength
At 25 psi, Rmax® Below Grade resists pressures from soil loads that act on the foundation wall while maintaining superior thermal performance.

Application Installation Instructions

Below-Grade Exterior Wall Application

Below-Grade Blind Side Wall Application

Project Profiles

Residential Construction

RYAN HOMES, RIVER RUN
Exterior Wall & Foundation Application

Ryan Homes builds every house as if it were their own, with the utmost care and commitment to craftsmanship, quality, and safety. They look for the same high standards when choosing insulation for below-grade walls and foundations.

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Commercial Construction

BOISE ISD FACILITY
Under Slab Cold Storage Application

The Boise School District Facilities & Operations (F&O) Department comprises over 300 hard-working individuals whose mission is to maintain safe, clean, comfortable, and conducive learning for more than 25,000 students.

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Residential Construction

MALM, CUSTOM BUILD
Exterior Wall & Foundation Application

With a commitment to excellence, efficiency, and safety, Malm Construction needed high-quality insulation to meet the project’s rigorous demands while aligning with financial goals.

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Let’s Talk Polyiso

Homeowner and first-time general contractor Wally Bruner shares his experience with Rmax® Below Grade insulation for his high-performance home project at Yellowwood Ridge, Indiana. Discover why he believes Rmax offers unmatched performance and customer service in the insulation industry.

Casey Malm from Malm Construction shares his positive experience with Rmax Below Grade insulation for construction projects in Polson, Montana. Discover how Rmax's thinner profile insulation offers cost-effective, high-performance solutions for below-grade applications.

Product Resources

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