Russell, John2000 is exactly right. Using square edged and leaving a gap the width of a nail is best. But I remember a lot of porch floors that were done with T & G flooring. The secret is to lay the flooring according to the temperature and humidity when you are laying it. If you lay the floor after a hot, dry week in Missouri and butt it up tight,you will have cracked flooring next summer. You can lay it butted tight when the weather and the wood has been in high humidity for a while--a week or more and out of direct sun.