The leaning tower of Pisa is becoming a very common theme out there and we are often getting calls from people having their recently installed (not by us) retaining walls failing after only a season or two. Contractors and homeowners are improperly installing and draining their retaining walls. Contractors probably know better (I hope) and choose to deliberately take short cuts to save on what is expected to be a long lasting installation. Homeowners aren’t expected to know, but should do as much research as possible before installing a retaining wall. For whatever option, be it concrete, block, brick, or rock, a properly prepared and compacted foundation is important. What is most important in our Northern climate is drainage, which is often neglected and the primary reason retaining walls push out, crack and undermine with time.
Case in point, see the following retaining wall and paver installation in Sudbury, ON.
Case in point, see the following retaining wall and paver installation in Sudbury, ON.
Upon reviewing the installation, there was no evidence of a weeping tile exit, which one would have expected to drain out the bottom far side of the wall around the large field stone pieces. It is possible that the contractor forced water back towards the weeping system of the house, however, this should only be used as a last resort when dealing with below grade installations such as excavation for a basement entrance. Maybe there is no weeping system or maybe they didn’t even use drainage rock behind the wall, which is ideally clean crushed material that provides structural support (due to the interlocking of jagged faces) and drainage properties (due to voids created by the jagged faces). The weeping tile drainage system is a perforated pipe that is installed at the base, behind the wall, to lead water away from the rear of the wall. Water behind the wall will expand when it freezes and will push the wall out as seen in this example. Also, over time, water running behind the wall will undermine or erode the material behind the wall and the wall itself. The final thing you need is landscape fabric to ensure that the soil behind your wall and the drainage rock doesn’t infiltrate over time and fill in your drainage rock rendering the system useless. There was landscape fabric protruding right at the retaining wall, but where was it installed? If there is no drainage material behind the wall then it is not helping anything.
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If one looks further, you can see the upper paver section (belonging to the neighbor) has sunk down and shifted. It is easy to assume that whatever existed before as a retaining wall was simply removed and this wall built in its place. By removing the existing wall, the soil behind is disturbed and instantly loses compaction. A bunch of soil would have to be removed to make room for granular drainage material and the installation of weeping tile. This clearly wasn’t done as the neighbours paver section was never touched in the process. This installation is falling apart and ruined whatever the neighbor had. Doesn’t help those great neighbourly relations people try to keep.
Always remember, base preparation, base preparation! Did I mention base preparation? Don’t let your contractor show up with an undersized compactor. It is pointless to have someone compact with a small plate tamper for a driveway or preparing for a garage pad foundation. Large roller compactors with a water ballast are best for increased compaction, not to mention speed and efficiency of installation. The base needs to have a certain amount of crushed material to a certain depth based on expected height/weight of the wall. There are tables for this. Be weary of contractors using the same thickness of base for all applications, unless they are being very generous. You shouldn’t be compacting large thicknesses of base at once either. This is to be done in smaller thicknesses (called lifts) to ensure you are getting proper compaction. Base design and installation is whole a science. Don’t let it be ignored.
At this point, two years after the installation, good luck getting the original contractor to return to remedy the situation. A reputable one wouldn’t have to come back for this scenario, as it would have been installed properly the first time.
We won’t know until redoing the whole installation properly as it’s not surviving the Sudbury climate. There are ways around re-doing a whole wall that was not installed properly, but this is only before damage is truly apparent. There is no way to repair the scenario mentioned above without a complete removal and replacement.
This same contractor performed a landscaping job at the same property along the waterfront. They did not account for the rising of the water levels throughout the season, so the first tier has washed away. This is a $20,000 mistake and guess who is now paying for it? There are optimal times to do these projects and winter is not one of them. Unfortunately, these homeowners will have to bare with this eye sore for a few more months before we can tackle it for them.
Stay tuned for our next article related to this from the -Engineering & Construction team
At this point, two years after the installation, good luck getting the original contractor to return to remedy the situation. A reputable one wouldn’t have to come back for this scenario, as it would have been installed properly the first time.
We won’t know until redoing the whole installation properly as it’s not surviving the Sudbury climate. There are ways around re-doing a whole wall that was not installed properly, but this is only before damage is truly apparent. There is no way to repair the scenario mentioned above without a complete removal and replacement.
This same contractor performed a landscaping job at the same property along the waterfront. They did not account for the rising of the water levels throughout the season, so the first tier has washed away. This is a $20,000 mistake and guess who is now paying for it? There are optimal times to do these projects and winter is not one of them. Unfortunately, these homeowners will have to bare with this eye sore for a few more months before we can tackle it for them.
Stay tuned for our next article related to this from the -Engineering & Construction team
