If you like your neighbors and can't bear the thought of moving but you need more space perhaps adding on is the solution. Adding on to your home can also add value when you go to sell if you do it properly. The key is to make sure what you add on is done in a way that makes sense with the floor plan and flow of the house. It also needs to fit the architectural style of your home.
Often I see a house where a fourth or fifth bedroom has been added in a weird location - do you really want to walk through the closet to get the guest room? That may add function for your needs but don't count on it adding value when you go to sell. Buyers may not want that additional bedroom enough to deal with the odd access.
If you do decide to add a room go into the project with your eyes open to the costs. A basic bathroom addition might only cost $20,000 but if you are adding a luxury master bath it could be more like $90,000. Here is a good article on rough costs.
In addition to the costs there are the issues of time and inconvenience. Many a friend has joked, "We stayed married through the kitchen remodel so we can make it through anything." Yes, they were joking but remodeling or adding on can be very stressful if you already have a complicated life.
While it may be the perfect solution for your needs, and could add value when you sell, before you decide to add on be sure you consider all the aspects of the project and make sure it isn't just easier to move!
