From:
Tomas Lipps <tmlipps@zzzzzzzzzzzzz>
Date:
Thu, 3 Nov 2005 12:58:41 -0700
Subject:
slip form masonry
Greg, at al, hi
or should I say, whoops.
I didn't intend to send that email in response to your slip-form
query, but did, inadvertently. the delay in this follow-up has
occurred because I don't really have time just now to delve into the
subject (even though it really deserves delving into) but I will
enlarge on it briefly. I should make it clear that I'm not an
expert, just an opinionated practitioner with particular pet peeves.
(alliteration unintended) hence the crutches comment.
Quoted text begins. The reason I tried out the slip form method is the easy way in which
reinforcing steel and concrete can be integrated with the wall in a
"monolithic" nature.
End of quote.
all I really meant to say is that you could have achieved the same
result without using a wooden form, bracing, etc.
Quoted text begins.In the approach you suggest (also the one used in the book The
Stonebuilder's Primer)
End of quote.
is that Charles Long's book? in which he advocates having one fixed
(inside) form only? if so, yes. I think that's an intelligent way to
build.
Quoted text begins.you end up with two dissimilar walls. One of one and mortar, one of concrete.
End of quote.
not really, mortar and concrete are both cementacious materials. and
can bond. and if the "tails" of some of the wall stones extend back
into the concrete - more integration. the backing doesn't have to be
concrete either, it can be more mortar, lime based mortar and scrap
rock.
but I was merely suggesting another way of achieving something
acceptable to structural engineers - using properly laid stonemasonry
as (permanent) formwork for reinforced concrete. (I once designed a
40 foot tall tower, actually a solid column, that would have used
this technique. it was approved by structural engineers -though
never built, unfortunately)
the efflorescence, resulting from moisture bearing salts to the
surface of the wall, is something I don't technically understand
(perhaps someone will enlighten us?) and, fortunately have never been
bothered with (I evidently must be doing something right?) but if
water is prevented form getting into or behind the wall, it should
help prevent that happening.
your comments about lime-based mortars and load-bearing stonemasonry
open a whole other subject. one that I am hesitant to go into here
(a good subject for an article in STONEXUS magazine someday) the
building permit process (which in the US varies from county to
county, even city to city, in some states) specifications, engineers'
approval, etc. is complicated, but I have to say that structural
engineers have cause for caution, the integrity of a stone wall
depending as it does on the knowledge and skill of the individual
mason(s) who build it and the specifications to which they work.
some engineers, however, can be persuaded to sign off on plans if
they can be convinced of the quality of the masonry. adherence to
traditional practices such as those exemplified in older buildings
that have stood the test of time could affect their decision.
something I learned at one of the Stone Foundation's annual
symposiums is that there is more at stake than a wall's ability to
bear a load. tensile strength is a concern. hence the
reinforcement. an east coast architect who spoke there has designed
buildings with traditional load-bearing stone walls (14 inches thick
if memory serves) the integrity of which were enhanced by reinforced
concrete bond beams. the building codes in the area in which these
were built evidently allowed this and/or he knew an understanding
engineer. the fact that he had a reputable contractor doubtlessly
helped. (and it should be mentioned that his houses were remarkable
different in appearance than those with a 4 or 6 inch stone veneer)
this may pose more questions than it answers, but I hope it furthers
the discussion.
Tomas
- Follow-ups
- message 00222: slip form masonry - Greg Carter (04 Nov 2005)
- message 00220: slip form masonry - daedelus lanthanien (03 Nov 2005)
- References
- message 00191: ZippyVideos video file sharing - Simon (30 Oct 2005)
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