Are you planning to do seismic retrofitting without first addressing the settlement issues?
I think there are many customers these days who are considering earthquake-resistant renovations. However, you need to be careful, as there are some contractors who do shoddy work.
Some time ago, I received a call from a client in Kochi Prefecture who said, “I’m planning to have seismic retrofitting work done, but before that, I’d like to fix the fact that my house has started to tilt due to ground subsidence.”
So far, this is a common scenario. And this homeowner’s decision is the right one. That’s because some unscrupulous seismic retrofit contractors try to carry out seismic retrofit work without first correcting any settlement issues.
In fact, a few years ago, an architectural designer I met in Chiba Prefecture approached me with the following request.
"The older house I'm designing and renovating is leaning due to ground subsidence, but the contractor in charge of the seismic retrofit says, 'If you tamper with a leaning house the wrong way, it could actually make it weaker, so let's just reinforce it as is.' Is that really okay?"
...There's clearly no good reason for that, right?
Even an elementary school student can tell which box is more likely to tip over: the one placed on a flat table or the one placed on a table slanted like a slide. So why do earthquake-proofing contractors make such terrible judgments?
There are two reasons for this.
First, this seismic retrofit contractor is uninformed and doesn't know how to handle the situation.
Second, even though they know this, they’re glossing over it because if the budget goes toward subsidence remediation work, their own contract amount will decrease.
Estimated Cost of Settlement Correction Work by an Earthquake-Resistant Renovation Contractor
Getting back to the client, this client explained it to me like this.
"An earthquake-resistant renovation contractor told me, 'Since the ground has subsided, we need to perform subsidence correction work first.' So I got estimates from two companies that could do the subsidence correction work, and both quoted similar amounts: 1.6 million yen and 1.8 million yen."
"Hmm? Were there really that many specialized contractors in Kochi Prefecture?" I wondered to myself as I listened to the client’s story.
“However, this seismic retrofit contractor told me, ‘If you have us handle everything, we’ll take on the settlement correction work for 500,000 yen. “We’ll have our own carpenters do the work instead of subcontracting it.” The price is so attractive that I’m having a hard time deciding. So, even though I know this is very presumptuous of me, I called you—Mr. Okamoto, a renowned house-moving craftsman from Kochi Prefecture—to ask for your advice.”
I probably just think I’m famous because I’m on TV a lot—though that’s probably just a misconception (laughs)—but I am an expert in subsidence remediation work. Anyway, as usual, I started by talking about “a comparison of the taste and price of udon from chain restaurants versus specialty shops,” and then I went on to explain the following.
"I think even a carpenter could do similar work if they handled it carefully. However, just as a chef uses top-quality ingredients and tools, we bring plenty of specialized tools with us to the job site to ensure a thorough installation. When it comes to installing the house after it’s been lifted into place, we use a mixture containing a specialized adhesive to ensure that the existing concrete and the newly poured sections don’t form a cold joint, and to prevent shrinkage from creating gaps after it dries. This results in a truly impressive finish.”
Subsidence Correction Work by House-Moving Specialists That Impresses Carpenters at Earthquake-Resistant Renovation Companies
Thirty minutes after I hung up, you called me again.
"I talked it over with my mom, and we'd like Mr. Okamoto to take a look at it. Would that be possible?"
I’m truly grateful for this opportunity. In the end, the homeowners accepted my quote of 2 million yen for this project. Although my quote was higher than those of the other two companies, I was able to fix issues that they hadn’t noticed when they provided their estimates.
"Wow, that's amazing! To fry them so perfectly without cracking the walls at all!"
The carpenters, who were scheduled to carry out the seismic retrofit later, came to observe the work while it was in progress so they could learn from the experience.
"Take a look at this jack. It's tiny, but I'm using it just right."
"Ma'am, I don't know what our boss said, but you made the right call by hiring a professional craftsman. Even if we tried, we couldn't do it this well."
At this job site, the client’s quick thinking led to a positive outcome, but that’s not always the case. And just because someone is a professional doesn’t mean you should take everything they say at face value.
After all, you’re the one who cares most deeply about your own home and can think through everything from your budget to how you’ll use it in the future.
