Sealing around uPVC window frames helps prevent draughts, heat loss and water ingress, improving comfort and energy efficiency throughout the home.

What you’ll need

uPVC-compatible sealant (silicone, hybrid polymer or paintable frame sealant), caulking gun, wipes or damp cloth, masking tape (optional).

Preparation

• Remove any old sealant, dust, grease and dirt from the frame and surrounding surface.
• Clean with a damp cloth or uPVC-safe cleaner and allow surfaces to dry completely.
• Apply masking tape along the frame and wall, leaving a 5–10mm gap for a neat finish.
• For gaps wider than 12mm, insert a foam backer rod before sealing.

Application

• Cut the nozzle at a 45° angle to suit the joint size and load the cartridge into the gun.
• Apply a continuous, even bead of sealant along the joint, working smoothly from top to bottom.
• Tool the sealant immediately using a damp finger, soapy water (for silicone), or a smoothing tool to press it firmly into the gap.

Finishing

• Remove masking tape while the sealant is still wet.
• Wipe away excess sealant or residue with a damp cloth.
• Allow the sealant to cure for 12–24 hours before touching or exposing to moisture.

Key tips

• Use low-modulus neutral cure silicone or hybrid sealants for exterior frames.
• Choose paintable frame sealant for interior joints that will be painted.
• Seal during dry conditions for best adhesion and performance.
• Inspect seals annually and replace any that show cracking or shrinkage.