We are in the process of building a 12x32ft redwood deck. It will have a 12x12 enclosed porch w/gabled roof and a step up octagon on the opposite side of the porch. We graded the soil underneath the deck away from the house and put a 6ml plastic liner on top and put 2-3in. of gravel on the top of that. We are using excellent materials on our deck and we have been very concientious about keeping water away from the house. I've looked at alot of deck designs. Most either use lattice, solid 1x or 2x stock or nothing at all for underpining. We have a 3-4ft. drop from the top of the deck to the bottom of the grade. I would like to use solid stock for underpining around the octagon and lattice under the rest of the deck. I am worried about the air movement with the solid underpining. Should I be? Are there any alternatives for underpining that I have not mentionded. Thanks for your incite. Angie B.