With the fine weather finally here, it’s time to look at improving the exterior of your house. Adding a deck is perhaps the favorite do-it-yourself project. With a little planning, you can spend the summer in comfort and safety on your new deck. A common mistake is to make the deck too small. Allow 20 square feet for each person who will use the deck. For a patio table and chairs, allow 60 square feet per person. Around furnishings, provide …