What's the best way to do this? Below is from Eric Gurney 7/21/2000 which is the best I could find with google...

From http://www.custombuildingproducts.co...derBoard12.htm
(link no longer good)

Fasteners: Galvanized roofing nails, 1 1/2" (38 mm) long with hot-dipped
galvanized coating for use with wood framing. Nails should meet Federal
Specification #FF-N105B/type 2 style 20. Custom Concrete Backerboard Screws
or equivalent, 1 1/4" (32 mm) long, for use with wood or 20 gauge steel
framing.

Underlayment: Using a 1/4" (6 mm) square-notched trowel, apply a setting bed
of latex-modified mortar to the subfloor or base. Immediately laminate 1/2"
WonderBoard Concrete Backerboard to subfloor base, leaving a 1/8" - 3/16"
(3 - 5 mm) space between boards at all joints and corners. Stagger joints so
they do not line up with underlying substrate joints. Fasten backerboard
every 6" - 8" (15.2 - 20.3 cm) o.c. throughout board field and around all
edges while setting bed mortar is still workable. Around perimeter of each
board, locate fasteners within 1/2" - 2" (1.2 - 5.1 cm) of edge. Fill all
joints and corners solid with latex-modified mortar. Taping of floor and
counter joints is not required.

Sam