Save this DIY for later đ¤ This vinyl trim window mullion DIY is one of the easiest ways to make builder-grade windows look custom for under $30. I used peel-and-stick vinyl trim to create a classic grid window mullion in the living room, then did a cottage-style diamond mullion in the kitchen for extra charm. Same affordable DIY, two completely different window styles. If youâre looking for a budget-friendly window upgrade, removable window mullions, or a renter-friendly DIY that adds character without replacing windows, this one is worth trying. The vinyl trim cuts down to size, peels, and sticks directly onto a clean window surface â no power tools and no permanent commitment. Perfect for adding cottage vibes, classic window grids, European-inspired details, or an easy custom look to builder homes. This DIY works great for living room windows, kitchen windows, and anywhere you want that cozy, old-world feel without the cost of new windows. LTKhome LTKDIY BudgetDIY WindowMullions CottageStyleHome BuilderGradeToCustom HomeImprovement AffordableHome DIYHomeProjects InteriorInspo