Step 6 · Seal All Joints and Connections

Apply a continuous bead of high-quality, exterior-grade gutter sealant to all areas where gutter sections connect, end caps are attached, and downspouts join the gutter outlets. Also, seal any joints between downspout sections if necessary. Smooth the sealant with a putty knife or gloved finger to create a clean, watertight seal. Allow the sealant to cure completely according to the manufacturer's instructions before exposing the gutters to heavy rain.