5/4 in. x 4 in. x 10 ft. Tongue and Groove Pine Decking Board
Often porch joists that boards are nailed or screwed to are spaced 24& 34; on center. 5/4 thick boards would have divination . 2 by decking would need to be used to prevent this or additional joists added to have 16& 34; o. c. The tongue and groove prevents cracks between the boards when they shrink in summer usually.