Products : Surface Prep : Waterproofing Membranes & Underlayments : SpiderWeb® II Seam Tape

SpiderWeb® II Seam Tape

SpiderWeb® Seam Tape is a fast and easy way to cover seams and changes of plane when installing the SpiderWeb II Uncoupling Mat to provide waterproofing and vapor barrier protection. Apply to smaller areas for full surface coverage to provide a durable protective layer under tile installations.

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Key Features

  • Required for a waterproof installation of SpiderWeb II Uncoupling Mat
  • For seams and changes of plane
  • Part of a waterproof/vapor barrier control system for floors


  • 100% waterproof protection for substrates
  • Easy to cut, hang, and adjust
  • Suitable for all tile types
  • Designed for use with modified thin-set mortars


TDS Documents

Technical Data Sheet


Conformance to Building Codes

Installation must comply with the requirements of all applicable local, state and federal code jurisdictions.

Environmental Consideration

Custom® Building Products is committed to environmental responsibility in both products produced and in manufacturing practices. Use of this product may contribute to LEED® certification.

Suitable Tile Types

Suitable for all tile types

Suitable Substrates

Use on the seams of the SpiderWeb II Uncoupling Mat only

Health Precautions

Wear impervious gloves and eye protection while using this product. Avoid contact with eyes or prolonged contact with skin. Wash thoroughly after handling. If eye contact occurs, rinse cautiously with water for several minutes, remove contact lenses if easy to do: continue rinsing. Immediately seek medical advice if symptoms are significant or persist. Do not take internally. KEEP OUT OF REACH OF CHILDREN.

Limitations to the Product

SpiderWeb II Seam Tape is not intended for use without a suitable substrate that can support the finished floor installation.

Application of Product

Install SpiderWeb II Uncoupling Mat according to product instructions. To minimize installation duration, measure and cut the seam tape to size with a utility knife ahead of mixing thin-set for installation. Once the mat is installed, apply thin-set mortar into the top of the uncoupling mat where the seam tape will be applied. Using the flat side of a trowel or a taping knife, embed the SpiderWeb II Seam Tape into the still wet thin-set. Work the trowel or taping knife at angles out and away from the center taking care to work out any air that may have been trapped when the seam tape was placed. 

Cleaning of equipment

Clean tools and hands with water before material dries.

Product Maintenance

Properly installed product requires no special maintenance. Do not use as a wear surface.

Ordering Information


  • 4.5" x 4.5" x 16.25' (11 cm x 11 cm x 5 m) Roll
  • 4.5" x 4.5" x 98.5' (11 cm x 11 cm x 30 M) Roll

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