Lumber is perishable, so treat it right if you’re not building within a week or two after delivery. Dry, ventilated and shaded storage conditions are key. What most people don’t realize is how the seemingly logical approach of wrapping lumber with a tarp is actually an invitation to mold. Fully enclosed tarps trap humidity around the pile as it rises from the ground, so tarps are a bad idea.
Start by laying 36” to 72” lengths of 4x4s or triple thicknesses of 1 1/2”-thick scrap lumber parallel to each other and three or four feet apart as a base. If you don’t have an airy building to stack in, choose a flat, shaded, sheltered spot. Place one layer of new lumber on this base, with small gaps between each board along the board edges. Place thin strips of wood on top of this first layer to separate and ventilate under the layer you’ll add next. Any strip size from 1/4” to 3/4” thick does the job, placed three or four feet apart, as you did with the base strips. Continue stacking with strips, building a second pile if your first gets three or four feet tall.
If your pile is not in a ventilated outbuilding, finish up by creating a roof over your lumber to protect the top from sunlight that causes cracks and warps. Weighed down pieces of old plywood, weathered pieces of junk lumber or pieces of metal roofing all work well.