Boeing BMS 8-346 Waterseal Tape Guide
Boeing BMS 8-346 Aircraft Waterseal Tape — Type & Class Explained
What BMS 8-346 covers, how to read a Type I / II, Class 1 callout, and the Patco D9100 polyurethane waterseal tape that meets it — in stock with free US shipping and a Certificate of Conformance.
Boeing Material Specification BMS 8-346 covers pressure-sensitive, flame-retardant waterseal tapes used to seal floor joints in the wet areas of an aircraft cabin — galleys, lavatories, and entryways — where moisture would otherwise reach the floor structure and cause corrosion. The qualified product for the common Type I & II, Class 1 callout is the Patco D9100 / D9100SW — a tough, clear polyurethane film tape that can be applied directly over wet sealant and stays put under foot traffic.
Already know you need it? View the Patco D9100 product page and data sheet.
Patco D9100 →What the BMS 8-346 callout codes mean
A BMS 8-346 callout is written by Type and Class. Your drawing will specify which combination is required; the most common waterseal requirement is Type I & II, Class 1. Here is what each part of the callout refers to:
The pressure-sensitive waterseal tape form covered by this guide — a tough polyurethane film with a urethane adhesive, for floor-joint moisture sealing in wet cabin areas.
A related construction within the same specification. The Patco D9100 is qualified to both Type I and Type II, so one product satisfies a Type I or Type II Class 1 callout.
The standard waterseal class the D9100 is qualified to. This is the class most floor-joint and wet-area callouts reference.
A separate, higher-grade class within BMS 8-346 covered by a different product. See the note below — the D9100 is qualified to Class 1, not Class 3.
Patco D9100 covers Type I & II, Class 1. Because it is qualified to both Type I and Type II, the same product line satisfies the standard Type I or Type II, Class 1 waterseal callout — including the self-wound D9100SW variant for linerless application.
Class 3 callouts: BMS 8-346 also includes a separate Type I, Class 3 branch, which is met by a different, higher-grade product — not the D9100. If your drawing specifically requires Class 3, contact us — we can advise on the correct product and lead time, but a Class 1 tape cannot be substituted where Class 3 is specified.
Patco D9100 / D9100SW — specifications
The qualified product for BMS 8-346 Type I & II, Class 1. Values are typical, from the current Patco (Berry Global) data sheet.
| Product | Patco D9100 / D9100SW — Flame Retardant Aircraft Waterseal Tape |
| Construction | Single-coated polyurethane film, urethane adhesive (D9100SW is the self-wound, linerless variant) |
| Backing | Polyurethane (PU) film |
| Color | Clear (transparent for visual inspection) |
| Liner | Kraft paper release liner (D9100); self-wound, no liner (D9100SW) |
| Total thickness | 9.0 mil |
| Weight | 8.6 oz/yd² |
| Adhesion to steel | 40 oz/in |
| Tensile strength | 70 lb/in |
| Operating temperature | −65 to 300°F |
| Flammability | FAR 25.853(a) |
| BMS 8-346 class | Type I & II, Class 1 |
| Other approvals | Airbus ABD0031 Para 7.3.2 & 7.4; Airbus AIMS 10-05-004A (ABS 5093); Fokker FK05-193; FAR 25.853(a) |
Typical values are stated at time of manufacture and are not for use in writing specifications. Always verify against the controlling drawing and the current manufacturer data sheet for your application.
What BMS 8-346 waterseal tape is used for
Per the manufacturer data sheet, the Patco D9100 is used for:
| Floor-joint sealing | Sealing floor-panel joints on aircraft decking in wet areas — galleys, lavatories, and entryways |
| Moisture barrier | Preventing moisture ingress to the floor structure, helping inhibit corrosion |
| Over wet sealant | Can be applied directly over wet sealant; repositionable during application |
| High-wear protection | Surface protection for high-traffic areas; tough, abrasion-resistant film |
| Sound damping | Secondary sound-damping in floor and panel applications |
| Visual inspection | Transparent film allows the sealed joint to be inspected without removing the tape |
Sealing a galley or lavatory but don't see BMS 8-346 on the drawing? Some wet-area callouts specify a galley wet-seal tape rather than a Boeing waterseal spec. Our Patco 1800 galley tape is a flame-retardant PVC wet-seal tape for those applications (Fokker FK05-159/160, FAR 25.853(a)). It is not a BMS 8-346 product — confirm your drawing's callout before choosing.
Need the data sheet or a cross-reference? Download the official Patco spec sheet from our Technical Data Sheets library, or see how this spec sits among the others on our Specifications by Authority page. The D9100 also meets FAR 25.853(a) for interior flammability.
Frequently asked questions
What is Boeing BMS 8-346?
BMS 8-346 is a Boeing Material Specification for flame-retardant, pressure-sensitive aircraft waterseal tapes used to seal floor joints in wet cabin areas such as galleys, lavatories, and entryways. The tapes act as a moisture barrier that helps protect the floor structure from corrosion, and must also meet FAR 25.853(a) flammability requirements.
Which tape meets BMS 8-346 Type I & II, Class 1?
The Patco D9100 (and the self-wound D9100SW variant) is the qualified product for BMS 8-346 Type I & II, Class 1. It is a clear polyurethane film tape with a urethane adhesive, also approved to Airbus ABD0031, AIMS 10-05-004A, Fokker FK05-193, and FAR 25.853(a).
What is the difference between BMS 8-346 Class 1 and Class 3?
Class 1 is the standard waterseal class the Patco D9100 is qualified to, covering Type I and Type II. Class 3 is a separate, higher-grade branch of BMS 8-346 met by a different product. A Class 1 tape cannot be substituted where a drawing specifically calls out Class 3 — contact us with your callout and we will confirm the correct product.
What is the difference between Patco D9100 and D9100SW?
They are the same polyurethane waterseal tape. The standard D9100 is supplied with a kraft paper release liner; the D9100SW is self-wound (linerless) for faster, waste-free application. Both are qualified to BMS 8-346 Type I & II, Class 1.
Can BMS 8-346 tape be applied over wet sealant?
Yes. The Patco D9100 is designed to be applied directly over wet sealant and is repositionable during application, which is part of why it is used for floor-joint sealing in galleys and lavatories. Always follow the applicable maintenance procedure for your aircraft.
Does BMS 8-346 waterseal tape meet FAA flammability requirements?
Yes. The Patco D9100 meets FAR 25.853(a), the FAA interior flammability vertical-burn criteria, in addition to its Boeing BMS 8-346 qualification. Always confirm current values against the manufacturer data sheet for your specific application.
Need a BMS 8-346 quote or a cross-reference?
Send us your spec callout (Type and Class), width, and quantity and we'll confirm the right Patco waterseal product, stocked sizes, lead time, and pricing. Certificate of Conformance available on request.
Ask Our Team →Specification details are provided for reference and are drawn from the current Patco D9100 / D9100SW technical data sheet. BMS 8-346 is a Boeing Material Specification; Boeing and BMS are trademarks of The Boeing Company. Airbus, ABD, ABS, and AIMS are trademarks of Airbus; Fokker is a trademark of its respective owner; Patco is a brand of Berry Global. Typical test values are stated at time of manufacture and are not for use in writing specifications. Always verify requirements against the controlling drawing and the current manufacturer data sheet before purchase.