Retaining wall damage & privacy damage identification, troubleshooting, cures.
This article describes the different types of damage that can occur to different types of retaining or barrier walls. Damage ranges from cosmetic (lime staining on wet privacy walls) to catastrophic if a tall retaining wall collapses. We discuss frost and water damage to all types of outdoor walls, and rot damage to wood retaining walls.
This article series describes types of privacy walls, retaining walls and retaining wall guard railing requirements, guard railing construction and building codes, and critical safe-construction details for retaining wall guardrails.
We include definitions of important retaining wall terms such as wall surcharge, and we provide diagnostic descriptions & photographs of types of damage to retaining walls & privacy walls.
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Don't ignore warnings of imminent collapse of retaining walls
Watch out: in at least some locations collapsing retaining walls can be dangerous. In 2007 the New York Times reported that a 50-foot-high retaining wall behind a hilltop home on Staten Island collapsed, sending
"... an avalanche of concrete blocks weighing hundreds of pounds each into the yards of smaller homes below. A car and a home at the base of the hill were damaged and people in four houses were evacuated, but no one was hurt,...] 
The same news article reminded readers that in May 2005 a 150-foot section of a nearly 100-year-old retaining wall above the Henry Hudson Parkway in Manhattan. Parked cars were buried and traffic on the parkway was not only disrupted for hours, but a detour around the repair project lasted for months.
Just the debris removal alone cost more than $1 million. It is noteworthy that there had been early warnings of a problem - sinkholes and voids had appeared behind the wall at least two months previously. Experts had also observed that a new drainage system, intended to relieve the pressure of ground-water build-up behind the retaining wall had not been effective.
Our photo above illustrates a retaining wall that is not in danger of collapse, but nonetheless we can see that water penetrates this wall - notice the little plant growing right out of the wall surface. This wall is located in Boca Raton, FL (or in English, Rat Mouth FL).
Examples of Earth Pressure & Frost-Damaged Masonry & Concrete Retaining Walls
Our photographs below illustrate the two most common types of damage to masonry retaining walls: leaning/bulging/bowing (below left), and frost cracking (below right).
Watch out: the mere presence of weep holes in the face of a masonry retaining wall does not guarantee that the wall won't be destroyed by earth pressure or increased pressures from wet soils and frost. Good drainage behind the wall and weep openings that are kept free running are needed.
How to Distinguish Between Frost Heave & Earth Pressure Damage to Masonry Retaining Walls
The poured concrete reinforced retaining wall shown at below left is cracking vertically from earth and frost pressure just above its tiny drain opening.
We suspected that the bottom of this wall may have been placed on a footing that was not below the frost line. A shallow wall footing combined with water and (in freezing weather) frost heaving, can be broken and heaved by those forces.
We can often distinguish between vertical frost heave damage and horizontal earth pressure damage to a retaining wall by noticing that frost heaving alone will typically leave the wall face flat in the vertical plane, that is, frost heaves alone won't cause the wall to bulge or lean outwards.
Back in 1986 my dog Katie helped inspect the curved masonry block retaining wall shown at above right. The stair-step cracking in that wall was accompanied by outwards leaning at the wall center and was caused by horizontal earth pressure combined with an absence of any drainage behind or through the wall face.
In the vertically-cracked concrete retaining wall at above left, notice that where the steel reinforcing re-bar placed horizontally in the concrete happened to run closest to the surface, exfoliating rust has caused spalling of the concrete surface. See FOUNDATION CRACKS & DAMAGE GUIDE for an extensive description of types and causes of masonry foundation and wall damage.
Rot Damage to Wooden Retaining Walls
Our low wooden retaining wall photograph (left) illustrates a common rot location that begins at the cut ends of the retaining wall members.
In the center of the photo you will observe the remains of a rotted anchoring retaining wall member as well.
How to Spot Fake "Treated, Rot-Resistant" Landscape Ties that are Rot-Prone
Watch out: wood retaining walls made of "landscape ties" that were not really treated-through with a wood preservative (i.e. are not pressure-treated lumber) are often sold to un-suspecting customers by spraying the wood surface with a green dye.
Dying or staining the exterior of untreated lumber green and then placing it in ground contact does not make for a long-lasting structure in most climates.
Because of its cross sectional size (6" x 6" or larger), some landscape tie lumber appears to have been treated with wood preservative only superficially.
The original end cuts may look "green" having been sprayed superficially at the treatment processing plant but the internal cross section of the wood may be discovered to have not been penetrated by the preservative chemical.
A second retaining wall rot indicator, fungal growth, is shown in photo at left.
If you see mushrooms or tree-ears growing out of a wood retaining wall you can safely assume that the wood is more rotted than meets the eye.
A rotted wood retaining wall may be more costly to repair than you'd first guess, particularly if excavation back into the retained earth is required to install new retaining wall anchors.
But you can observe a clue that will assist in evaluating the rot and insect resistance of the lumber by noticing the extent of penetration through the wood wherever you have made a fresh saw cut through the member.
Water Damage to Retaining Walls & Privacy Walls
At the beginning of RETAINING WALL DAMAGE we describe catastrophic retaining wall collapses traced to water loading behind the wall.
Water accumulating behind a retaining wall adds significant weight to that of the earth already present (the wall surcharge as we explain at RETAINING WALL DEFINITIONS).
Our photo at left illustrates lime or calcium deposits staining an above-ground privacy wall in Surprise, AZ. I suspect that a plant sprinkler system on the other side of the wall is soaking the masonry in this area - a theory that is supported by the reader report and photos of a different home described just below.
Reader Question: how can I stop water from a neighbor's sprinkler from seeping through my privacy wall
I have an unusual question. But please bear with me as I explain my story: We had a brick wall put up a couple of months ago. My next door neighbor waters her plants almost every day and when she does she is constantly spraying my wall. We’ve asked them several times if they could just move their sprinkler back a couple of feet so it won’t damage the mortar.
Their reply was “We can do what we want in our yard”. So now you know what kind of people we’re dealing with. I’ve contacted our County Health Department to see if we could get them on a “wasting-water ordinance” but unfortunately according to [statutes in my state], they are NOT wasting water. So now I’m left with my neighbors damaging my wall.
I’ve attached a few photos to show what my side of the wall looks like. It’s horrific! Since my wall is so close up against their chain-linked fence, we can’t get to it to spray it with some kind of water sealant.
So my question is: Is there anything we could slip between my wall and their fence to take the brunt of the constant water exposure? The only thing we come up with is some kind of sheet metal (but that would rust?) or some type of Plexiglass? or thin sheets of wood (would rot?) This is my dilemma. Is there anything I’m not thinking of that would work? Any suggestions would be greatly appreciated.
P.S. I do not want to take my neighbor to court and sue for property damage if I can help it. That’s the very last resort. - Anon. 10/31/2013
Reply: try corrugated fiberglass roof panels of an appropriate color, placed vertically on the sprayed side of the block wallThank you for the interesting question - it may be unusual to you, but it's not rare for there to be a bit of a dust-up between neighbors over water and more over boundary issues. It's a shame. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer or suggestion than we can give by email alone. That said I offer these comments:
Your wall looks like concrete block, not brick. The significance is that concrete block is more porous and so admits more water passage through it more quickly than a brick wall would.
You are spot on target in wanting to either move the sprinklers back on the neighbor's side (you could offer to pay that cost) but I am doubtful that would be a complete cure as it'd be difficult to water plants right against the other side of your wall without wetting the wall somewhat.
You are also spot on target in thinking about putting a barrier on the outside of your wall. Since there is chain link fence in the way on the other side of your wall, coating it would be a mess, and may raise more neighbor issues as you'd have to be in their yard and trampling their plants to do so; and coatings constantly soaked by a sprinkler are not long-lived anyway.
I would choose a rigid plastic or fiberglass sheet material that can slip between the chain link fence and the block wall, on the outside of the wall, extending from ground to a height equal to the top of the chain link fence or top of your wall - whichever is lower.
In choosing a plastic or fiberglass material it needs to be self supporting unless the space between chain link fence and block wall is very small (say 1/2" or less); for self supporting material, take a look at white or green corrugated fiberglass roof panels. You can even give your nasty neighbor a vote on whether they would prefer to look at white or green.
Other plastics such as rigid plastic used by basement de-watering companies like B-Dri is not self-supporting and would have to be affixed to the wall - not feasible in the case you describe.
I share your disappointment in the neighbor, but frankly just fixing the problem on your own will be less upsetting and far less costly than litigation or a fist fight. Though a good smack might be tempting.
Retaining Wall Articles
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Frequently Asked Questions (FAQs)
Question: retaining wall damaged by nearby buried oil tank
21 January 2015 mike rose said:
i am going to check for soil contamination the tank is from 1964 and the tank was abandon in 1992.and is still in the ground and has a sink hole developing above it.can i do anything
If an "abandoned" buried oil storage tank is collapsing that is certainly a potential hazard in several regards and it has not been properly abandoned.
Details about proper oil storage tank abandonment, regulations, and safety or environmental concerns are found at OIL TANK ABANDONING PROCEDURE
I suspect that what your neighbor might have is a document stating that there was no evidence of leakage - which would have permitted the tank to be abandoned in place. But that abandonment, properly conducted, would have included cleaning the tank and filling it with sand or another suitable material.
To check for soil contamination one would need to collect soil samples close to the tank and to a depth of the tank's bottom.
If necessary notify the owner and building authorities of a small but potentially dangerous local sink hole condition as a child or possibly even an adult falling into such an opening could be very serious, even fatal.
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