You should caulk gaps, cracks, or joints in areas where you want to keep water and/or air out in your home. The list below includes common places where caulk/sealant is needed: Penetration in the attic floor, knee walls, and cracks where air can enter/exit from the outside Windows and doors Chimneys Basement rim joists (where the foundation meets the wood frame) Where faucets or pipes meet the house Cracks in exterior siding or where two different materials meet (e.g., siding and chimney or foundation) Around air vents and ducts Penetrations in the walls such as electrical wiring and outlets, plumbing, recessed lighting, and phone or TV cables Leaks in gutters or cracks in flashing Kitchen sinks, faucets, backsplashes, countertops Bathroom tubs, showers, along top of shower surround, backsplashes Between crown molding, baseboards, chair rails and wallboard