Last year, almost 40% of our projects included replacing a failed retaining wall, some of those walls less than 10 years old. We don’t typically take photos during demolition to show the owners why the wall failed, but we constantly see the reasons and we take every precaution with NSWS® walls to make sure it doesn’t happen. And that’s why NSWS® walls come with a lifetime warranty.
This blog post is a warning to property owners everywhere that just like with most things in life, you get what you pay for.
We don’t make it a habit to criticize other contractors’ work, but we couldn’t help it in this case. This contractor can remain anonymous but it took everything I had not to knock on that poor homeowner’s door to warn them about their doomed new retaining wall that wasn’t even finished yet!
Basically, there are so many things wrong with this wall that it inspired a blog post. What most people will see as they drive past is the stone work, but what most people don’t know is the reason this stone wall is destined to fail is hidden behind it.
The effects are not immediate, this owner is probably going to be satisfied immediately after the job is finished and even pay this contractor. But the real problems will arise after just a few winter seasons.
The specific factors that set this wall up for failure in this particular case have to do with complete lack of drainage, geogrid reinforcement, footings and structural backfill, all very crucial components of a structurally sound retaining wall.
You can see from the pictures, that not a single drain pipe or weep hole was installed. No footing was installed prior to building this wall. Also, building the wall and backing it with mortar against the original clay soil will result in significant movement of this wall during the coming winter months. Furthermore, they are building this wall completely vertical with no batter to it.
Our only (very frustrating) assumption is that this contractor provided a low bid to get the job and cut costs where the customer could not see. Depending on the site, these “invisible costs” are usually about 25% of total wall cost. This company eliminated a significant amount of site work, footing, drainage and backfill requirements. Unfortunately, with none of those precautions taken, this wall will see significant differential settlement and there is no doubt in our minds that it is only a matter of time before its imminent failure.
So homeowners, please remember that just like a good book needs to have more than a pretty cover – a beautiful stone wall needs to be structurally sound to last you generations.
And for your future stone wall projects remember that even small retaining walls have to contain enormous loads and withstand our harsh New England winters.
A structurally sound retaining wall must meet the following two requirements:
- The wall is structurally capable of withstanding the earth pressure applied to it – this means structural backfill and proper drainage and at least a 3-4° batter.
- The foundation of the wall is capable of supporting both the weight of the wall and the force resulting from the earth’s pressure acting upon it – this means a proper footing (see our last post about footings).
And this is just another reminder that not all walls are created equal.