Seam & Bedding Compounds / Putties

What Are Marine Seam & Bedding Compounds and Putties?

Whether you're fitting out a classic wooden cruiser or sealing deck hardware on a fiberglass sailboat, seam and bedding compounds are among the most essential—yet often overlooked—products in a boater's maintenance arsenal. These specialized materials serve as the critical barrier between your vessel and the relentless intrusion of water, filling gaps, sealing joints, and cushioning hardware against the flex and movement that every boat experiences underway.

What Do These Products Do?

Seam compounds are formulated specifically to fill the gaps between planks, keel joints, and hull members in wooden boat construction. A quality seam compound must remain flexible long after application, allowing planks to naturally expand and contract with changes in moisture and temperature without cracking or losing adhesion. Bedding compounds are typically used when installing deck hardware, joinerwork, and through-hull fittings—anywhere water could find a path through a fastener hole or a joint between dissimilar materials.

Unlike permanent adhesives, many bedding compounds are designed to stay semi-flexible for years, creating a watertight seal while still allowing hardware to be removed for inspection or replacement down the line. Surfacing putties, on the other hand, are sanded smooth and used as a cosmetic fairing layer ahead of a final paint coat, bridging small imperfections in hull surfaces before painting.

Key Considerations When Choosing a Compound or Putty

• Above or below the waterline: Not all compounds are rated for continuous submersion. Always verify a product's suitability for below-waterline use before applying it to hull seams or keel joints.
• Flexibility vs. permanence: Semi-paste, slow-oxidizing compounds remain workable and can be disassembled later, while polyurethane-based products bond so aggressively that removal can damage the surrounding surface.
• Surface compatibility: Wood, fiberglass, and metal each interact differently with compound chemistry. Confirm compatibility before application, especially when bedding hardware onto cored decks.
• Paintability: If the compound will be overcoated, check that it accepts antifouling or topside paints within a reasonable window after application.
• Cure time: Some compounds touch-dry in a couple of hours but require 24–36 hours before accepting a paint overcoat—plan your project timeline accordingly.

Interlux Paint: A Trusted Name in Marine Seam Compounds

Interlux Paint is one of the most recognized names in marine coatings worldwide. Founded in 1881, Interlux has spent well over a century developing coating solutions engineered specifically for the marine environment. Their seam and bedding compound lineup includes both white and brown seam compounds suited for wooden boat seams and keel joints—products that remain durable and flexible after immersion to absorb the natural expansion and contraction of hull planking. Interlux also offers surfacing putties designed to be applied before final paint coats, helping boatbuilders and refitters achieve a smooth, professional finish on wooden and fiberglass surfaces alike.