The cost of building a dormer will depend on a variety of factors including the size and complexity of the dormer, local labor and material costs, and the specific design of the dormer. For example, larger dormers and those with intricate designs will typically be more expensive than smaller and simpler designs. Additionally, the cost of building a dormer can vary depending on the materials used, such as wood, metal, or composite materials. Additionally, the cost of building a dormer may also depend on the complexity of the installation, such as if additional structural support is needed or if specialized tools are required.