http://www.forestry.state.al.us/Publications/TREASURED_Forest_Magazine/2006%20Fall/Wildlife%20Hotel%20-%20The%20Art%20of%20Building%20a-Functional%20Brush%20Pile.pdf

A well constructed brush pile will
accommodate a variety of wildlife and
starts with (as most all building projects)
a firm foundation. The basic brush pile
has a foundation formed by building a
base of larger decay-resistant material
that will support the weight of the pile.
Large logs, field rocks, cement blocks

old pipe or tires can be used for this. The
base materials should be about 6 inches
in diameter and placed about 10 to 12
inches away from each other, wide
enough apart to provide easy access
within the interior of the pile.