Whether you're flipping a house, planning to live there short term and sell in the near future, or renovating to improve the home according to your personal preference, there are certain renovations which are proven to add value to the house. Value can be determined by the functionality and desirability of the work you have conducted. Personalized features don't tend to add as much value as replacing anything which is worn with new features.
New Windows and Doors
Windows and doors need to be new and function properly in order to sell the house at its full value. Double hung windows are the standard system for modern houses and are perfectly fine for standard usage. New windows open and close smoothly, stay open, lock securely, and are available with additional security features. Upgraded windows can add additional value if properly planned according to their intended function. Likewise, doors can be fairly standard or upgraded to match the rest of the house and the neighborhood.
Porches and Decks
Porches and decks need to be on the house according to the designs and in good order according to local building code. Most people, whether they actually use a deck regularly or not, appreciate a nicer deck than what a contractor may have generically built as an afterthought when constructing the house. Adding size and features to a deck will add value to the home. Patios as well have certain expectations. Some people want a large enough patio to set groceries down on their way in, some people prefer a patio be screened in instead of open. A great contractor will understand what types of deck and patio improvements add value to the house if you plan to sell as well as what upgrades have added personal value for other customers.
Finishing Touches: Siding and Roofs
Siding and roofs are pretty easy to evaluate. As long as they look nice and don't have any leaks, they're probably okay. If they are older and faded, new roofs and siding won't really add value to the house as much as assure the full value is achieved in a sale and help the house sell faster because of curb appeal. Of course, it will impress the potential buyer to know you've recently replaced either so they know they won't have to soon after their purchase.