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Johns Manville DynaLastic 250 S Base Ply or Flashing Sheet – SBS-Modified Bitumen Roll, 39-3/8 in. x 32 ft 10 in.
Regular price $119.00Orders start at $399 — combine any items to reach the minimum. Learn more
Johns Manville DynaLastic 250 S Base Ply or Flashing Sheet – SBS-Modified Bitumen Roll, 39-3/8 in. x 32 ft 10 in.
JM DynaLastic 250 S is a polyester-reinforced SBS-modified bitumen base or ply sheet for multi-ply roofing systems and flashing, supplied as one roll 39-3/8 in. wide by 32 ft 10 in. long. Its SBS rubber-and-asphalt blend gives the sheet elasticity and recovery to handle roof expansion and contraction. Meets ASTM D 6164, Type II, Grade S.
Key Features:
- SBS flexibility: High-quality SBS rubber and asphalt blend lends elasticity and flexibility to the sheet.
- Movement capable: Elongation and recovery properties accommodate continual roof expansion and contraction.
- Polyester reinforcement: Heavy-duty mat with bidirectional glass-scrim reinforcement offers robust tear strength and puncture resistance.
- Wind and hail performance: Reinforced construction supports high wind performance and an excellent hail rating.
- Dimensional stability: The sheet exhibits strong dimensional stability.
- Parting agent surface: A fine material parting agent is applied to both sides of the product.
- Code compliance: Meets the requirements of ASTM D 6164, Type II, Grade S.
Specifications Table:
| Specification | Details |
|---|---|
| Brand | Johns Manville |
| Sell unit | 1 roll, 39-3/8 in. x 32 ft 10 in. |
| Product line | DynaLastic 250 S |
| Dimensions | 39-3/8 in. x 32 ft 10 in. roll |
| Length | 32 ft 10 in. |
| Width | 39-3/8 in. |
| Material | SBS-modified bitumen with heavy-duty polyester-reinforced mat (bidirectional glass-scrim) |
| Surfacing | Fine material parting agent on both sides |
| Intended use | Base or ply sheet in multi-ply roofing systems; flashing sheet |
| Approvals | Meets ASTM D 6164, Type II, Grade S |
Coverage & How Much You Need:
Each roll measures 39-3/8 in. x 32 ft 10 in., roughly 108 sq ft of sheet per roll; subtract laps and use the specified side and end laps for the system when sizing plies or flashing.
Fit and Compatibility:
Designed for use as a base or ply sheet in Johns Manville multi-ply (BUR and MB) roofing systems; pair with JM approved mopping, hot asphalt or cold adhesive systems and compatible membranes and flashings per the JM specification.
Frequently Asked Questions (FAQ):
Q: What is on one roll?
A: One roll 39-3/8 in. wide by 32 ft 10 in. long.
Q: Where is this sheet used?
A: As a polyester-reinforced base or ply sheet in a variety of multi-ply roofing systems, and for flashing.
Q: What standard does it meet?
A: It meets the requirements of ASTM D 6164, Type II, Grade S.
Q: What reinforcement does it use?
A: A heavy-duty polyester mat with bidirectional glass-scrim reinforcement for tear strength and puncture resistance.
Q: How much area does a roll cover?
A: Approximately 108 sq ft of sheet, less required side and end laps per the roofing specification.
Expert Verdict — Reviewed by the SuperArbor Pro Desk
Use DynaLastic 250 S where movement capability matters: the SBS blend's elongation and recovery handle thermal cycling better than plain ply sheets. Set rolls to relax, maintain specified laps and fully embed the sheet in adhesive or asphalt per the JM system spec. Its puncture and tear strength make it a strong choice for flashing details too.
Modified bitumen installation involves hot asphalt, torches or solvents depending on the system; follow JM application instructions and fire-safety requirements on the roof.
Order JM DynaLastic 250 S base ply or flashing sheet for flexible, reinforced multi-ply roof performance.
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