|
| |
Limestone online guide
Architectural Limestone online database and information for
architects, contractors and homeowners.
Articles includes installation procedures, attachments and materials.
Comparison of cost and quality of limestone, cast stone, and precast concrete
materials.
Cast stone is usually used in place of limestone for complex Architectural
moldings.
Cast stone is impossible to distinguish from some kinds of natural limestone.
What Is Limestone ?
Description: Limestone consists of fossilized shells, sediment, fishbone,
and H20.
- Many textures, saw cut, bush hammered, chiseled, cleft, polished (marble),
honed.
- Limestone has a broad range of color from gray/buff to cream/tan to bone
white.
- limestone is quarried in blocks, then cut into strips or carved by hand.
- Limestone is extremely expensive, usually prohibitively so, for
Architectural moldings.
- Usually used in a less expensive form, such as slab or paver applications.
Limestone is a
sedimentary rock that derives from the decomposition of (formerly) living
organisms.
Limestone is used mainly as paving or wall cladding, shapes which are easy to
cut with saws or split with guillotines.
The cost of hand carved Architectural moldings such as columns, door/window
trim, balustrade, wall caps is extremely high.
That is the reason cast stone is used as a substitute for Architectural
limestone moldings.
Limestone's are calcareous rocks made up of at least 50% of carbonate mostly in
the form of calcite, aragonite, and dolomite.
There are other carbonate varieties but these are not significant in the context
of building stone. As a group, these carbonate rocks represent about one-fifth
of all sedimentary rocks, occur on all continents, and span all ages from recent
to very old.
Although a large proportion of limestone's are bioorganic
(contain fossil material), there are also chemically deposited limestone's which
are important as building stone, namely travertine.
Other disadvantages of limestone when compared
with cast stone or precast concrete.
Acids are a fact of life and here to stay. There are many of them in
our home and in our environment. Wine, carbonated drinks, fruits and fruit
juices, vinegar, and even some natural waters will react with these carbonate
rocks. And there is little that we can do about it!! Many a posh resort and nice
residences with originally finely polished or honed limestone surfaces on their
bartops or kitchen-tops have discovered this.
Precast concrete is used in place of limestone bar/kitchen tops with better
resistance to staining and scratching.
Cast stone can also be used instead of limestone for bar/kitchen tops but needs
to be sealed as it has the same characteristics as limestone but is more
abrasion and stain resistant when sealed properly.
A characteristic of limestone's is their softness.
The softness is mainly a function of the mineral composition. Because of this softness, it can be
easily scratched by most things in the house such as cutlery, coins, tools,
keys, toys, etc., so there should never be the expectation that nicely polished
or honed limestone surfaces are going to stay that way for ever.
This is another reason to use precast concrete or cast stone in place of
limestone.
Precast concrete is extremely scratch resistant and cast stone, slightly less
resistant.
A physical feature of limestone's is its intrinsic
porosity.
Many limestone's, particularly the bioorganic ones, have a medium to
high degree of porosity. Porosities of 10-30% are not unusual in the French
limestone's and the famous Australian limestone from Mt Gambier has a porosity
of 50%.
But although technically weak and very absorbent, certain construction
techniques (both old and modern) allow them to be used successfully and
effectively. "In cold
climates, however, a porous limestone can suffer rapid degradation due to
freeze-thaw cycling and some protection
might be required".
One important structural aspect inherent in most
limestone's
Is the presence of very fine, squiggly lines which are often brownish.
These structures, called stylolites, are pressure-solution features formed
during the compaction and lithification of limestones. Mostly, the brownish
colour is due to hydrated iron oxide but there can also be concentrations of
clays and/or sulphides. Because these stylolites are natural planes of weakness
and can often transmit fluids because they are not fully closed, any expanding
clays can react to fluids and physically weaken the limestone.
R1: For description of surfaces:
a) rough :- as found in blocks from the quarry
b) sawn:- as cut in a circular block saw or in a gang saw
c) natural cleft :- as you find in natural slatestone and limestone, or any
stone which can be split into layers with chisel
d) bush hammered :-with a multi or single-pointed chisel
e) Chiseled :- with a chisel which leaves white line on hitting a stone surface
f) flamed :-with a flaming oxy-acetylene or oxy-CNG flame
g) sand-blasted :- hitting a stone surface with high-pressure compressed air
with fine sand
h) Polished
i) honed :- semi-polished. The above are few of the stone finishes u can ask
for.
j) pitched face :- where the sawed or quarried surface is removed leaving a
rough, irregular scalloped appearance.
k) chopped :- where a Guillotine - type piece of equipment is used to break the
stone again leaving a rough rock face exposed. JVC.
Limestone in California
Limestone installed in California city's such as
Los Angeles, Beverly Hills, Bel Air, Ventura or Santa Barbara has to be
mechanically fastened to the wood frame of a building usually with
stainless steel or galvanized attachments, this because of earthquake
codes. There are many historical buildings in California with
limestone as part of their facade. Limestone in
Los Angeles, Beverly hills, Bel Air, Ventura and Santa Barbara was at it's
most popular in the 1900's. In Santa Barbara, limestone, cast stone and precast
concrete were used
extensively in the downtown district and also in a primitive form at the
Santa Barbara mission in the form of adobe, a mixture of mud and straw or horsehair
mixed with water and hand shaped into molds. In the City
of Ventura, limestone was used mainly on churches in the downtown
area. In Los Angeles limestone was used in many important buildings including the
famous Los Angeles City hall. In Santa Barbara limestone, cast stone, precast
concrete and Santa
Barbara stone were used in conjunction in many historical buildings.
Santa Barbara stone also called Santa Barbara sandstone, is found mainly
in Santa Barbara county, is removed from the ground in loose form, the
Santa Barbara stone is then cut and shaped by a stonemason into useable
blocks. One of the better known Limestone, precast and cast stone
installers in this area is Regency Cast Stone
installers
of precast concrete in Beverly Hills and the grater Los Angeles area,
including Santa Barbara and Ventura. Precast concrete installers sometimes supply and install granite or
precast concrete by CDI
inc including precast, caststone and concrete design products
such as CDI columns. Ventura Cast
Stone make beautiful dry pack cast stone and precast concrete columns and balustrade,
California Precast info@californiaprecast.com make precast moldings, CDI inc manufacture
precast moldings and stairs. Installers also supply CDI precast
granite concrete
window and door trim, CDI GFRC columns, products from concrete design, full weight
precast
and granite or limestone products, Cast
Stone Co of California
manufacture precast columns resembling limestone.
Regency Cast Stone
installers of CDI precast pool coping, CDI precast
or limestone moldings
and CDI fireplace mantles usually use stainless steel attachment and bolts
to fix the limestone moldings directly through the stucco coating.
Some of the products exclusively
manufactured by other company's include mantels (some say mantels). Some
well known fireplace mantel manufacturers are
Sierra concrete design, Ventura Cast
Stone and Dura art stone, Stone legends,
Moonlight molds, Fineline precast, Concrete design inc, Studio cast
design, Concrete design inc, CDI, Limestone Architectural products, Haddonstone, include: cast stone
which resembles
limestone, precast concrete which can be painted or etched, precast which
is cast wet into molds, stone, limestone or sandstone in
los angeles areas such as Ventura, Santa Barbara. Los angeles precast
companies usually manufacture wet pour precast concrete and not many
manufacture dry pack cast stone.
Ventura Cast Stone is one such National precast concrete
manufacturer based in Ventura County and also install their products with
in house installers in the greater Los Angeles, Ventura and Santa Barbara
areas. Los angeles precast manufacturers such as
Cast Stone Co
make many styles of columns but
are usually made in wet pour precast, los angeles dry packing companies are few. Santa
Barbara has many fine precast projects to view, mainly downtown. Santa
Barbara stone is a yellow buff color and is easily replaced with less
expensive cast stone, Santa Barbara stone is found naturally in the Santa
Barbara County area, and is processed and sold in Ventura by Santa Barbara
Sandstone Co. Santa Barbara City and the surrounding areas also boast many
fine Abode columns, especially at the Santa Barbara mission
(see history of cast stone and concrete) . Ventura City
has many fine limestone and sandstone facades in the downtown Main street
area.
-
|
