While many homeowners love the idea of building an ADU to give them more space and more flexibility, there are disadvantages too. Disadvantages can vary depending on your situation so you should consider general disadvantages as well as ones that relate to your situation. For example, converting a garage into an ADU may mean losing a parking space for a car. Some general disadvantages of building an ADU include: You may lose storage: Whether you convert a garage or build a separate ADU you may lose usable space or storage. Disruption of your daily life: If you use this as a rental property, you will need to deal with the repairs, maintenance, and anything else that comes with having a tenant. This can be a hassle if you do not make enough for a property manager. The cost of construction: While an ADU may be more affordable than other options, there is still an initial investment that you will need to consider.