There’s nothing like staying home for a few months to make the house feel too small. Square footage can be added to a home by the standard method of building out into the yard; adding a second floor over all or part of the house; building a room over the garage (a popular option); finishing the basement, or converting the garage to conditioned living space.
How you decide to do it depends on budget available, your property size, and the building codes in your area.
A good contractor can advise you on what would work best for your situation, and handle the permitting process for you as well. Some CAD drawings will ensure that you and he/she are visualizing the exact same thing!
Here is an addition we built for a Bellingham/ Whatcom county client. Check out our website for more photos of additions.