stone pergola

[Norman Watts <Norman_Watts@zzzzzzz>]

Simon,

I have nothing to do with the pergola myself. The man just tells me how
he plans to build it. He did say there would be stainless steel pins
holding the lintels in place on top of the uprights. But there are
things I wonder about.

-Are uprights (18" square and 11' tall) stable if set on a proper
reinforced concrete platform? They are in the ground 1', but
essentially there is no lateral support. But then, maybe something that
weighs over 4000 lbs is pretty stable. And there are four of them, tied
together by lintels. I forgot to mention there will be 4' stainless
steel rods through the lintels and into the tops of the uprights.

-Does granite have the tensile strength to span 10 ft with when it has
an 18" x 18" cross section? That part seems odd to me. So yes, I think
he should talk to an engineer, but I don't think there would be many
who know something like that. I've certainly never seen granite used
that way anywhere.

Norman Watts, Ph. D.
National Institutes of Health
50 South Drive, Rm. 1509
Bethesda, MD 20892-8025
Phone: (301) 402-3418
Fax: (301) 480-7629