My home is built on and follows the terrace drops of my lot. There is first the street/parking level, then a drop down to the level of house entrance,then another drop down to the lower floor of the house and then three more terrace drop downs from the back yard. It is the second terrace that has been maintaind for over 30 years by an L-shaped railroad ty (sp?) wall (about 5 feet tall on the short side and stairstep progression on the long side) that has, of course, began to deteriorate at this point. I need to decide on what retaining wall material is the best to replace this system. I have been advised that if I use timber, pine or cedar, that I can probably maintain the plateau directly above with the same measurements it has now which accomodates my only location for a patio table and 4 chairs. A stone wall, though more permanent and preferred by city zoning, would cause probably an 8-12 inch loss of the plateau...just enough to make the plateau unusable and force me to then build a deck above the L-shaped drop down . So, what timber would be my best choice for long term maintenance? Do they make a composite type, like that used in decking, that would be strong enough?