Stone Masonry Construction
A Brief Overview
Traditional Dry-Stack Stone Walls:
Stone Masonry originated with dry-stacked stonework
where the walls are carefully laid up without mortar.
Gravity serves as the glue that holds everything
together. Free-standing dry-stack stone walls are
usually made larger at the base and then taper in slowly
as the height increases. For absolutely no expense but
the labor, farmers built miles upon miles of stone
fences this way in Ireland and in the northeastern
states.
Many old Irish houses were built in a similar
way. Where "mortar" was used, it was often
merely mud or limestone plasters with little strength.
The mortar functioned as caulking to stop the flow of
air, rather than as cement to bond the stones together.
Short, dry-stacked stone walls are especially ideal for
landscaping projects. Taller walls require more skill
and time. For more details on dry-stack stone walls,
Traditional Mortared Stone Walls:
Mortared stone walls evolved out of dry-stack stone work
with the emergence of cement mortars. The first cements
were made of burnt gypsum or lime mixed with water to
make a paste with slight bonding capability. Stone walls
still had to be built as carefully as they were without
mortar. The cement paste just filled the gaps between
the stones and cured to form a soft, rock-like
substance.
The basic formula for modern cement
originated in England in 1824. It is called
"Portland cement" because the color is similar to the
rocks on the English island of Portland. It is still
called Portland cement everywhere in the world it is
manufactured. This cement is made with calcium from
limestone or chalk, plus alumina and silica from clay
and shale. The ingredients are ground, mixed in the
right proportions and burnt in a kiln at a temperature
of about 2500 degrees F (1350»C) to drive out water
bound up in the raw materials. In the kiln it fuses into
chunks called clinker. It is cooled and powdered, and
gypsum is added to control how fast it sets up. Portland
cement is mixed with sand and water, and often lime to
make a smooth mortar for stone and brick work. Adding
the lime makes the mortar softer and more flexible.
With the aid of Portland cement it is possible
to build a taller stone wall that does not taper inward
like a dry-stacked wall. The cement has some ability to
"glue" a stone wall together with less care, but proper
stone working techniques are still important. Building a
free-standing stone wall is a true art and requires a
lot of time and skill to do it well.
Veneered Stone Walls: Most stonework
today consists of a non-structural veneer of stone
against a structural wall of concrete or cinderblock.
Concrete consists of Portland cement mixed with sand,
gravel and water. The larger particles of gravel
interlock like little fingers to make the concrete
resistant to cracking. Steel reinforcing bar can be
added to serve as much longer "fingers" to make a wall
that is very resistant to cracking. Concrete is a fast
and relatively inexpensive way to put up a structural
wall, so few people take the time for labor intensive
traditional mortared stone walls any more.
Instead, the structural wall is put up first,
and thin, flat stones are essentially glued onto the
face of the wall with cement mortar. Metal tabs
in the structural wall are mortared in between the
stones to tie everything together, otherwise the
stonework would just peel right off the wall. The
structural wall serves as a form on one side of the wall
to make it really easy to lay up the stonework, provided
the rocks have good flat edges to work with.
Slip form Stone Walls: A slip formed
wall might be described as a cross between traditional
mortared stone wall and a veneered stone wall. This is
the method of stone Masonry we have used the most. Short
forms, up to two feet tall, are placed on both sides of
the wall to serve as a guide for the stone work. You
place stones inside the forms with the good faces
against the form work and pour concrete in behind the
rocks. Rebar is added for strength, to make a wall that
is approximately half concrete and rebar and half
stonework. The wall can be faced with stone on one side
or both sides. With slip forms it is easy even for the
novice to build free-standing stone walls.
Retaining Walls, contractors,
retaining walls, RALEIGH NC wall builders, construction,
installers, RALEIGH NC drainage systems, soil erosion,
lake walls, garden areas, Retaining wall Structure in
the foreground is called a "mud box", a type of
retaining wall built to hold flood waters in check. A
retaining wall is a structure that holds back earth from
a building or other structure. Retaining walls stabilize
soil and/or rock from downslope movement or erosion and
provide support for vertical or near-vertical grade
changes. Cofferdams and bulkheads, structures that hold
back water, are sometimes also considered retaining
walls. Retaining walls are generally made of masonry,
stone, brick, concrete, vinyl, steel or timber. Once
popular as an inexpensive retaining material, railroad
ties have fallen out of favor due to environmental
concerns
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