RL Sanborn Masonry
repairs,restores and builds
retaining walls in the
Portland Maine area.
Many material options for
retaining walls are available,
such as stone , brick &
concrete block.
Call for a free estimate.
(207) 479-7567
repairs,restores and builds
retaining walls in the
Portland Maine area.
Many material options for
retaining walls are available,
such as stone , brick &
concrete block.
Call for a free estimate.
(207) 479-7567
Masonry Blog What is masonry? Masonry is the building of structures from individual units laid in and bound together by mortar. The common materials of masonry construction are brick, stone such as marble, granite, travertine, limestone; concrete block, glass block, and tile. Masonry is generally a highly durable form of construction. However, the materials used, the quality of the mortar and workmanship, and the pattern the units are put in can strongly affect the durability of the overall masonry construction |
A retaining wall is
a structure that holds back soil
or rock from a building,
structure or area. Retaining
walls prevent 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.
Segmental retaining walls
have gained favor over
poured-in-place concrete walls
or treated-timber walls. They
are more economical, easier
to install and more
environmentally sound.
The most important
consideration in proper design
and installation of retaining
walls is that the retained
material is attempting to move
forward and downslope due to
gravity. This creates lateral
earth pressure behind the wall
which depends on the angle of
internal friction (phi) and the
cohesive strength of the
retained material, as well as
the direction and magnitude of
movement the retaining
structure undergoes.
Lateral earth pressures are
typically smallest at the top of
the wall and increase toward
the bottom. Earth pressures
will push the wall forward or
overturn it if not properly
addressed. Also, any
groundwater behind the wall
that is not dissipated by a
drainage system causes an
additional horizontal
hydrostatic pressure on the
wall.
As an example, the
International Building Code
requires retaining walls to be
designed to ensure stability
against overturning, sliding,
excessive foundation pressure
and water uplift; and that they
be designed for a safety factor
of 1.5 against lateral sliding
and overturning
a structure that holds back soil
or rock from a building,
structure or area. Retaining
walls prevent 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.
Segmental retaining walls
have gained favor over
poured-in-place concrete walls
or treated-timber walls. They
are more economical, easier
to install and more
environmentally sound.
The most important
consideration in proper design
and installation of retaining
walls is that the retained
material is attempting to move
forward and downslope due to
gravity. This creates lateral
earth pressure behind the wall
which depends on the angle of
internal friction (phi) and the
cohesive strength of the
retained material, as well as
the direction and magnitude of
movement the retaining
structure undergoes.
Lateral earth pressures are
typically smallest at the top of
the wall and increase toward
the bottom. Earth pressures
will push the wall forward or
overturn it if not properly
addressed. Also, any
groundwater behind the wall
that is not dissipated by a
drainage system causes an
additional horizontal
hydrostatic pressure on the
wall.
As an example, the
International Building Code
requires retaining walls to be
designed to ensure stability
against overturning, sliding,
excessive foundation pressure
and water uplift; and that they
be designed for a safety factor
of 1.5 against lateral sliding
and overturning
Gravity
Gravity walls depend on the weight of
their mass (stone, concrete or other
heavy material) to resist pressures
from behind and will often have a slight
'batter' setback, to improve stability by
leaning back into the retained soil. For
short landscaping walls, they are often
made from mortarless stone or
segmental concrete units (masonry
units). Dry-stacked gravity walls are
somewhat flexible and do not require a
rigid footing in frost areas.
Earlier in the 20th century, taller
retaining walls were often gravity walls
made from large masses of concrete
or stone. Today, taller retaining walls
are increasingly built as composite
gravity walls such as: geosynthetic or
with precast facing; gabions (stacked
steel wire baskets filled with rocks);
crib walls (cells built up log cabin style
from precast concrete or timber and
filled with soil); or soil-nailed walls (soil
reinforced in place with steel and
concrete rods).
Gravity walls depend on the weight of
their mass (stone, concrete or other
heavy material) to resist pressures
from behind and will often have a slight
'batter' setback, to improve stability by
leaning back into the retained soil. For
short landscaping walls, they are often
made from mortarless stone or
segmental concrete units (masonry
units). Dry-stacked gravity walls are
somewhat flexible and do not require a
rigid footing in frost areas.
Earlier in the 20th century, taller
retaining walls were often gravity walls
made from large masses of concrete
or stone. Today, taller retaining walls
are increasingly built as composite
gravity walls such as: geosynthetic or
with precast facing; gabions (stacked
steel wire baskets filled with rocks);
crib walls (cells built up log cabin style
from precast concrete or timber and
filled with soil); or soil-nailed walls (soil
reinforced in place with steel and
concrete rods).
Cantilevered
Prior to the introduction of modern
reinforced-soil gravity walls,
cantilevered walls were the most
common type of taller retaining wall.
Cantilevered walls are made from a
relatively thin stem of steel-reinforced,
cast-in-place concrete or mortared
masonry (often in the shape of an
inverted T). These walls cantilever
loads (like a beam) to a large,
structural footing, converting horizontal
pressures from behind the wall to
vertical pressures on the ground
below. Sometimes cantilevered walls
are butressed on the front, or include
a counterfort on the back, to improve
their stability against high loads.
Buttresses are short wing walls at right
angles to the main trend of the wall.
These walls require rigid concrete
footings below seasonal frost depth.
This type of wall uses much less
material than a traditional gravity wall.
Prior to the introduction of modern
reinforced-soil gravity walls,
cantilevered walls were the most
common type of taller retaining wall.
Cantilevered walls are made from a
relatively thin stem of steel-reinforced,
cast-in-place concrete or mortared
masonry (often in the shape of an
inverted T). These walls cantilever
loads (like a beam) to a large,
structural footing, converting horizontal
pressures from behind the wall to
vertical pressures on the ground
below. Sometimes cantilevered walls
are butressed on the front, or include
a counterfort on the back, to improve
their stability against high loads.
Buttresses are short wing walls at right
angles to the main trend of the wall.
These walls require rigid concrete
footings below seasonal frost depth.
This type of wall uses much less
material than a traditional gravity wall.
Anchored
See also: Tieback (geotechnical)
This version of wall uses cables or
other stays anchored in the rock or soil
behind it. Usually driven into the
material with boring, anchors are then
expanded at the end of the cable,
either by mechanical means or often
by injecting pressurized concrete,
which expands to form a bulb in the
soil. Technically complex, this method
is very useful where high loads are
expected, or where the wall itself has
to be slender and would otherwise be
too weak.
See also: Tieback (geotechnical)
This version of wall uses cables or
other stays anchored in the rock or soil
behind it. Usually driven into the
material with boring, anchors are then
expanded at the end of the cable,
either by mechanical means or often
by injecting pressurized concrete,
which expands to form a bulb in the
soil. Technically complex, this method
is very useful where high loads are
expected, or where the wall itself has
to be slender and would otherwise be
too weak.
Types of retaining walls