Reliabilt-window-mull-kit-instructions Apr 2026

: Align the windows and press the mullion strip (the H-shaped or snap-on piece from your kit) into the channel. You may need a rubber mallet to gently tap the strip into place until it snaps securely.

Mulling is the process of joining two or more windows together to fit into a single large opening. If you are using a , the process involves preparing the frames, applying sealant, and securing the units with structural connectors. ReliaBilt Window Mull Kit Installation Steps reliabilt-window-mull-kit-instructions

: You can find series-specific PDFs (e.g., Series 105 or 150) on the ReliaBilt Installation Support page . : Align the windows and press the mullion

: Lay the windows side-by-side on a flat surface. Use a utility knife to trim any excess vinyl "welds" or protruding edges from the corners where the windows will meet to ensure a flush fit. If you are using a , the process

: If your windows have nailing fins or J-channels on the sides being mulled, remove them using pliers or a utility knife to allow the frames to sit tightly together.

: Open the window sashes to access the factory pre-drilled holes or specific reinforcement areas. Drive the provided screws through one frame into the other (staggering them if necessary) to pull the units tightly together.

: Apply additional silicone sealant to the top and bottom of the mull joint, filling any voids. If your kit includes a drip cap or mull bridge , install and seal these over the top and bottom exterior joints. Helpful Resources