Condo Media - June 2021 - 36

The Region

MAINE

The Invisible Wall

Site Walls Should Not be Out of Mind
[by Jack Carr, P.E., RS, LEED-AP]

There is no condominium community asset more overlooked than
its site walls. They literally become
part of the landscape and seem to disappear, yet they are vital to the health of
the community. They are sometimes
called retaining walls or sometimes
simply landscape structures, but in
the hilly interiors of Maine or the
rugged slopes of the coastline, these
structures allow the very existence of
some condo communities.
They can be made of many different
materials. They can be poured concrete,
steel, or timber. They can be concrete
block or stone or brick. They can be
very tall or very short. Whatever they
are, if they fail, they can be dangerous
and costly to repair. So, a prudent

grounds committee should schedule
regular inspections and maintain a
log of repairs.
INSPECTION SCHEDULE
AND CHECKLIST
It is recommended retaining walls be inspected four times a year, that is, before
or after each season. Heavy rains or soil
frost movement can have a significant
effect on a retaining wall in a short time.
At the very least, someone should perform an annual inspection and compare
those findings with the year before.
l Grounds Conditions
Like us, aging retaining walls deteriorate primarily because of gravity. This
can be due to the excessive soil loading

They are sometimes called retaining walls or sometimes simply
landscape structures, but in the hilly interiors of Maine or the
rugged slopes of the coastline, these structures allow the very
existence of some condo communities.
36

CONDOMEDIA June 2021

behind the wall or the weight of the
wall overloading the soil conditions
beneath the wall. The increase of forces behind the wall is often the result
of water build up due to surface water
above the slope percolating into the
ground or a raising ground water table.
Weep holes are designed to reduce this
increase in hydrostatic pressure, but
weep holes can be blocked by debris or
overwhelmed by the quantity of water.
One of the first steps in the inspection process is to observe the conditions of the ground surfaces upslope
of the retaining wall. Some walls have
trench or other types of drains to intercept the water while some ground
surfaces are designed to quickly drain
water over or around the wall before
it can enter the ground behind the
wall. If water ponding above the wall
is discovered, this problem must be
corrected. Ponding will occur if the
ground settles or is removed due to
erosion. If the top surface is paved,
cracking in the asphalt or concrete
surface can allow unintended water
to enter the soil.
l Retaining Wall Surfaces
The surface of the retaining wall is
the next and perhaps easiest element
to inspect. Wall movement should be
noted. Walls should lean back toward
the slope uphill. If they lean forward
or have signs of bulging in any locations this could indicate excess back
pressure or failure in the underlying
soils. Horizontal cracks are usually
more serious than vertical cracks.
The first time this is noted it should
be brought to the attention of the
facility manager or your engineer.
Timber retaining walls can move or
crack due to both earth movement and
insect attack. Timber wall elements
can rot with age. Any type of wall can
crack and allow vegetation matter to
grow from either side of the wall. All
roots, weeds, or other growth should
be removed when discovered, as they
can apply considerable pressure to the
crack and create localized weakening
of the wall. Wall cracks in concrete

Condo Media - June 2021

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