This story came from a professional builder in an area that has been swamped with Certified Installers. Experience is the best teacher and the homeowner learned a hard expensive lesson the same way.
What you are about to read is true. The names have been changed to protect the innocent.... and to keep us from getting sued! The facts are indisputable, the guilty have walked away (as usual!), and the end result is a client who has learned a valuable lesson.
But, the silver lining to this cloud is the fact that the client now has a retaining wail that will fall down only when the Great Wall of China does. Read on.
Let me introduce you to Bill and Kathy. Nice folks. Easy-going and, until last year, very trusting. They needed a retaining wall in their rear yard. Not just any retaining wall, mind you, but a big one. A $40,000.00 retaining wall. They called three landscapers, as we always recommend (except when they call us first!). One of them was us. One of them was a respected competitor. The last one was... let me see, what should we call them? Oh, I know.. How about We Don't Have a Clue Landscaping?
Guess who got the job?
The project entailed removing an existing railroad tie retaining wall and replacing it with a pre-cast segmental retaining wall system. Keystone was the chosen product The wall was to be a double-wall system, with a four foot (exposed) lower wall, a four foot (exposed) upper wall, and two sets of steps linking the lower backyard with the upper. Keep that word "exposed" in mind. We'll need it later.
The wall was designed by using pre-designed plans provided by the manufacturer, was presented to Bill and Kathy with a quote that was in the range of the other two.
Before we go further, time for a lesson:
The construction of any retaining wall, no matter how small or large, is conceptually the same. There are three critical factors:
Notice that I didn't say "footer". The footing of the wall is the base material that the wall sits on. The base of a retaining wall should be prepared by excavating to a predetermined depth (dependent upon the size of the wall) and placing crusher run to a predetermined thickness. Crusher run is the stone that is below your driveway. It is tamped so that it is a solid mass. The base must be thick enough and stable enough to prevent settling of the wall. This wall called for one foot of crusher run below the base.
2) Deadmen or Geogrid
When a timber wall is built, timbers are placed back into the slope, perpendicular to the wall. These use the weight of the soil to hold the wall up. Picture your extended arm buried into a slope. Hard to pull out, right? Same concept with deadmen. With a pre-cast segmental wall, a product called geogrid is used for this purpose. The geogrid is a plastic weaved product that extends from four feet up to 50 feet into the slope, depending upon the height and application of the wall. This wall called for two levels of grid (six feet and eight feet long) for each wall.
In our climate, it is absolutely critical that water is kept out from behind the wall. We do this by backfilling the walls with crushed stone and perforated pipe, to channel any water away. Grading the area above also serves to help keep the water away. Our freeze-thaw cycle is a wall-buster. This wall, as any other, called for 4" perforated pipe, wrapped in fabric, and covered with crushed stone to the top of the wall.
If a wall is built without any one of these factors, the wall will fail. Poor base preparation will cause the wall to settle. Insufficient geogrid will cause the wall to fall over from the weight of the soil behind it. Poor drainage will cause the wall to blow out from hydrostatic pressure and frost heave.
Sometimes failure will take time. It's sort of like an appliance warranty. After the warranty runs out, the appliance stops working. (How do they do that?)
Sometimes it happens pretty quickly.
Bill and Kathy's wall was built in November, 1995. In January, 1996, the wall started to fall. TWO MONTHS. What's wrong with this picture?
In January, 1996 after looking at the construction of the wall, I suggested that Bill and Kathy make two calls: one to an engineer, and one to a lawyer.
Initial observation of the wall showed that it did not have proper base preparation. Due to the size and configuration of the wall, it was recommended that two courses of block be buried below grade, on top of one foot of crusher run. The base of the lower wall was placed on top of four inches of half-inch crushed stone; not CRUSHER RUN, not buried, not installed right.
The lower wall was not backfilled with CRUSHED STONE; it was backfilled with sand, which has a moisture-retention of about 19%. The upper wall was placed on top of this sand, so it settled, and then fell down, because it had no GEOGRID. We figured that this travesty of a project was due to one of two things: either the installers didn't know or didn't care. It probably was a combination of the two.
Bill and Kathy had an engineer redesign the wall, according to the soil conditions, and the manufacturer's recommendations. We gave them a quote, based upon this design. Our quote to tear down and rebuild the wall with material supplied was more than our original quote to build it with us supplying the material. Getting sick yet? You haven't seen (or read) anything yet
We expected teardown and excavation for the new wall to take one week. It took two. Why? (sure, I know how to estimate!) Because We Don't Have a Clue landscaping, Inc. tied four downspouts from the back of the house into their drainage. Remember lesson 3? Remove water from the back of the wall. The whole rear roof was draining into the wall.
The whole roof was draining behind the wall. That amazes me more than anything else about this wall. We Don't Have a Clue.
You can probably imagine how wet it was behind the wall. There was the extra week.
As we continued to tear the wall down, we found no GEOGRID on one whole side (this was the side that failed in two months). We did find grid on the other side, but, because WDHAC did not remove all of the railroad ties, it was folded up on itself two feet into the grade, not EIGHT FEET as required. The railroad ties were still there, because they did not even excavate for drainage stone, which should extend two feet behind the wall. Therefore, why take out the ties?
This section of wall was nine feet tall, and was holding up a deck.
After eighteen years in this business, I thought I saw it all. Yeah, right
Diary Of A Wall
We finally removed all of the block and excavated for the lower wall to a depth of 28 inches below grade. This allowed for 12 inches of CRUSHER RUN and two courses buried. We had the engineer scheduled to inspect our excavation, our first layer of crusher, our second layer of crusher, and the first base course. Bill and Kathy took no chances, and I don't blame them. Three weeks later, we laid the last block and cut in most of the caps.
After the first three courses, we backfilled with CRUSHED STONE, tamping it in six inch lifts. It was critical to tamp the stone because the upper wall was going to sit on this stone. We laid in six-foot lengths of GEOGRID, and continued to build. After three more rows of block, we laid in eight-foot lengths of GEOGRID, on top of one foot of CRUSHER RUN (base for the upper wall). We continued in this fashion, until all two thousand (give or take) blocks were installed.
Each wall has two layers of DRAIN PIPE to drain away the water. We redirected the downspouts into their own pipes to carry the water far away from the base of the wall.
As of this writing, we still have to clean up the site and install approximately 100 yards of topsoil. Additionally, we have about 150 feet of natural stone walls to build for Bill and Kathy.
But, the hard job is done.
The wall will stay where we put it.
I'll make sure that my great-grandchildren check it out.
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