I want to build am 8 foot 2x4 framed wall finished with stucco across the entry way to my home to create a courtyard. The sidewalk is natural stone over a 4 inch concrete slab. Do I need a footer? When digging on each side of the sidewalk I discovered PVC irrigation pipes a few inches below ground level. (Freezing is not an issue here.) Can I pour concrete over and around these PVC pipes.