Bathroom Addition: Average Cost, $39,578; Value Added, $22,875
Having too few bathrooms in a house spells trouble for even the closest, most companionable families. Maybe that's why home buyers look more favorably on listings that have a roughly equal number of bedrooms and bathrooms. So, if you can swing it, plan for a full bathroom or half-bath addition. If there's no space to add a bathroom, renovating an existing bath is a close runner-up in terms of adding home value.