I'll hit all the reponses in one message here to avoid clogging up the
string between the tin cans:

Mark Rabinowitz,

The spalled areas on the treads are at the nosing, typically. There is no
evidence of settlement in the units themselves. The damage appears to be
from impact and freeze-thaw action.

Mike Devonshire,

Dutchman repairs look pretty appealing now. Like I said, I wasn't involved
in the specs, only in the review. I probably should have recommended that
dutchman repairs be looked into as an alternative. After all, Biltmore House
has a lot of stone in it. They have a long history of maintenance and
repairs, kind of like a medieval cathedral. I'm curious why they didn't
consider that approach. I'll ask and report back.

Mike Edison,

Thanks for your good thoughts on the mechanics of failure. With your
permission, I'm going to pass your message on to the owner.

________________________________
And now for some thoughtless pontificating:

I sometimes wonder if we are relying too much on patching mortars and epoxy
consolidation. Maybe we should take all the R&D money going into epoxies and
polyesters and acrylics and whatever and train some craftsmen to do
traditional repairs. Two in every state (we need three in NC -- we're a long
state).

Not totally unrelated to the current thread on stone repair, I attended an
interesting seminar in Winston-Salem, NC on wood preservation. John Stahl
(Advance Repair Technologies) gave an interesting lecture on epoxy repair
methods for wood. He came down hard on the typical saturation-consolidating
method and argued that all the deteriorated wood should be removed. His
proprietary epoxy trowels on pretty thick to make a pretty substantial
patch. However, I couldn't help but think that the preparation required was
similar to that for a traditional dutchman repair, just executed with
"modern" materials.

Of course, a traditional repair would require using a hand saw and a chisel,
which as we all know are very sharp and would require additional liability
insurance and more trips to the emergency room. So we get comfortable with
our flexible putty knives, knowing that anything can be glued back. Who
wouldn't like the patent rights to cyanoacrylate?

John Horton