RL Sanborn Masonry builds restores and repairs masonry retaining walls to
customer specifications and Maine building codes. Your satisfaction is 100%
Estimates available upon request.
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or call (207)619-7473 for more information.
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 mortar less 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: ego synthetic or with pre cast facing;
gabions (stacked steel wire baskets filled with rocks); crib walls (cells built up log cabin style from pre cast concrete or
timber and filled with soil); or soil-nailed walls (soil reinforced in place with steel and concrete rods).
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 buttressed on the front, or include a counter fort 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.
See also: Tieback (geo technical)
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.
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 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
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
|Types of walls
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,
block, glass block, and
tile. Masonry is
generally a highly
durable form of
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
|RL Sanborn Masonry 2014
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