Window Drainage Plane

Window Drainage Plane™


Need a custom detail?
Ready to order?

Window Drainage Plane
  • Window Drainage Plane
  • Window Drainage Plane
  • Window Drainage Plane

Window Drainage Plane Highlights

Window Drainage Plane™ prevents entrapped moisture below windows.  The sub sill region of windows is an especially moisture-sensitive area.  MTI’s Window Drainage Plane™ allows moisture to escape from the sub sill area before it can cause problems.



  • A unique product to drain moisture from the window sub sill area
  • Creates a slope-to-drain cavity in the sub sill region of a rough opening
  • Rigid, durable and long lasting
  • Provides LEED credit value with its 100% post-industrial recycled plastic

Window Drainage Plane Installation

  • Prepare bottom of window rough opening with proper slope-to-drain surface
  • Cut and place WDP on prepared surface at bottom of window; temporarily attach with dabs of construction adhesive
  • Flash window rough opening according to window manufacturer’s instructions
  • Install window
  • View installation animation for detailed instructions

Window Drainage Plane Ordering/Shipping

Contact MTI at 1-800-879-3348 for specific cost to your destination.

Window Drainage Plane Specifications

A 0.024" (0.6 mm) thick high-impact polystyrene strip formed with .120" (3 mm) deep corrugations, bent into L-shape, 5" (127 mm) wide by 9" (229 mm) high, to fit on top of sub-sill region of a window rough opening prior to window installation to facilitate drainage.

Product Number WDP 5000
Piece Length (Feet) 4
Pieces per Bundle 10
Linear Feet per Bundle 40
Bundles per Box 6
Linear Feet per Box 240
Boxes per Pallet 10
Linear Feet/Units per Pallet 2400/600
Pallet Size 48" x 40" x 55"