Washington What You Should Know: Adding an addition, deck, awning, or porch to your manufactured or mobile home can increase the value and aesthetic of your home. The state of Washington regulates the type and size of additions you can make to your manufactured or mobile home. There are three main types of additions and structures you can build for your manufactured or mobile home in Washington: decks, awnings, and porches. A deck is a platform made of wood or composite materials and is typically attached to the side of a manufactured or mobile home. Decks must be built according to the manufacturer’s specifications and must be properly secured to the trailer. The maximum size of a deck is 24 inches off the ground and must be no more than 400 square feet. An awning is a protective covering over a window or door. Awnings must be properly secured to the manufactured or mobile home and must be no more than 60 inches off the ground. A porch is an enclosed or semi-enclosed addition to the manufactured or mobile home. Porches must be built according to the manufacturer's specifications and must be properly secured to the trailer. The maximum size of a porch is 24 inches off the ground and must be no more than 400 square feet. When adding any addition, deck, awning, or porch to a manufactured or mobile home in Washington, it is important to check with your local building department or housing authority to make sure you are in compliance with all applicable codes and regulations.