Skip to content
Johns Manville DEXcell Cement Roof Board – 7/16 in. Cementitious Cover Board, 4 ft x 8 ft and 4 ft x 4 ft, Off White
Regular price $34.50Orders start at $399 — combine any items to reach the minimum. Learn more
Johns Manville DEXcell Cement Roof Board – 7/16 in. Cementitious Cover Board, 4 ft x 8 ft and 4 ft x 4 ft, Off White
Johns Manville DEXcell Cement Roof Board is a 7/16 in. thick lightweight cementitious cover board in 4 ft x 8 ft or 4 ft x 4 ft panels with an off-white face. Its high compressive strength and moisture, mold and mildew resistance make it ideal where wind uplift and puncture resistance matter. Sold per piece; install under single-ply membranes over insulation.
Key Features:
- Impact resistance: A lightweight cementitious core delivers exceptional impact resistance.
- High compressive strength: Exceptionally high compressive strength improves overall roof system performance.
- Moisture tolerant: The cement board withstands prolonged exposure to moisture.
- Mold resistant: Scores a maximum 10 for mold resistance when tested per ASTM D 3273.
- Fire performance: FM Class 1 for fire barrier requirements and UL Class A unlimited slope with excellent surface burning characteristics.
- Uplift and puncture defense: Ideal for systems where wind uplift and puncture resistance are a concern.
Specifications Table:
| Specification | Details |
|---|---|
| Brand | Johns Manville |
| Sell unit | 1 piece (PC) |
| Product line | DEXcell Cement |
| Available sizes | 7/16" x 4' x 8'; 7/16" x 4' x 4' |
| Material | Cementitious (cement-based) roof board |
| Color / finish | Off White |
| Thickness | 7/16 in. |
| Dimensions | 4 ft x 8 ft or 4 ft x 4 ft panels |
| Wind / fire / impact rating | FM Class 1 for fire barrier requirements; UL Class A unlimited slope |
| Approvals | FM Class 1; UL Class A; ASTM D 3273 mold resistance score of 10 |
| Intended use | Specialty coverboard under commercial roofing membranes |
Coverage & How Much You Need:
One 4 ft x 8 ft panel covers 32 sq ft and one 4 ft x 4 ft panel covers 16 sq ft before cutting and layout waste; divide the roof area by panel size to order boards.
Fit and Compatibility:
Used as a cover board over JM polyiso insulation beneath JM single-ply or multi-ply membranes; attach per the roofing system manufacturer's requirements (adhesive or mechanically fastened).
Frequently Asked Questions (FAQ):
Q: What sizes are available?
A: Two sizes: 7/16 in. x 4 ft x 8 ft and 7/16 in. x 4 ft x 4 ft.
Q: How much does one board cover?
A: The 4x8 board covers 32 sq ft and the 4x4 board covers 16 sq ft before cuts and waste.
Q: Can it handle moisture exposure?
A: Yes, the cement-based core withstands prolonged moisture exposure and scores a maximum 10 for mold resistance per ASTM D 3273.
Q: What fire ratings apply?
A: FM Class 1 for fire barrier requirements and UL Class A unlimited slope with excellent surface burning characteristics.
Q: How is it attached?
A: Follow the membrane system's specification for adhesive or mechanical attachment over insulation.
Expert Verdict — Reviewed by the SuperArbor Pro Desk
DEXcell Cement is the board to specify where job-site traffic, wind uplift or puncture risk is high, thanks to its high compressive strength and impact resistance. Choose the 4x8 size for fast coverage on open decks and the 4x4 size for easy handling in tight areas or around equipment. Stagger board joints and follow the membrane system's attachment pattern for rated performance.
Cement board edges and cut dust require gloves, eye protection and dust control when cutting; use proper roof fall protection during installation.
Specify JM DEXcell Cement Roof Board for high-strength, moisture-tolerant cover board protection on your next roof.
All third party trademarks, including logos and icons, referenced on our website and product pages remain the property of their respective owners. Unless specifically identified as such, Arbor's use of third party trademarks does not indicate any relationship, affiliation, sponsorship, or endorsement between Arbor Home and the owners of these trademarks. Any references by Arbor Home to third party trademarks are to identify the corresponding third party goods.
