Laminated constuction can (probably will) fail when the parts glued together
exapand and shrink with changes in moisture content, then water gets into
the open joints and causes decay. Pressure treated wood will not decay, but
it usually is lower quality wood that is more likely to expand and shrink.
The most long-lasting wood construction for square column bases (also known
as "plinths") is four solid wood pieces joined at the corners with a
splined-miter joint. I just made two such plinths, 12.5" x 12.5" x 2.25" out
of vertical grain Douglas Fir in my woodworking shop last week. It took 4.2
hours to fabricate the
plinths, which would cost $147. plus $50. for materials. I treated them with
chemical preservative inside and water repellant outside.
The method is described in my article, "Mr. Baseman," in Old-House Journal,
July 1995. If your library does not have it, I can send you a copy for $10.
to cover my costs and time.
Also, you can get plinths made of plastic, "cultured marble," and aluminum.
For more on column maintenance and repairs go to www.HistoricHomeWorks.com ,
click on Reports and see the Wooden Column publication, which shows
construction methods and lists suppliers.