Our clients’ home wasn’t that old, but their 4 deck support posts were out of plumb… to the point of being dangerous.
How often have you read about an upper deck failure when a deck’s floor assembly tears away from the house proper?
In this case the deck support posts were moving downhill. So the plane of the 8′ x 31′ deck itself was sinking the farther you walked away from the home’s exterior wall. Left alone the eventual stress would have torn the deck joists away from the rim joist secured to the house proper. NOT GOOD!The edge of the home itself was on fairly level ground, but the deck posts were located along a relatively steep slope heading pretty far down to a creek in Sudden Valley. The concrete piers supporting the 4 posts were poorly installed, and the original builder refused to take responsibility. Basically, the concrete piers were sliding and tilting downhill. Though it was clearly the builder’s fault, our clients had no legal recourse. So they called us to the rescue.
It turned out that the slope was considered a critical area, so we needed to consult with both a structural engineer (Bourne Engineering) and a soils engineer (GeoTest Services) for proper engineering, permitting and construction. Adaptations Design Studio created the permit drawings and documents.
The solution involved hammering pin piles into the ground so as to achieve the resistance necessary to build super-sized concrete piers that would encapsulate the older concrete piers.
Check out the images we took during construction. The pin piles, furnished and installed by our sub Foundation Restoration, bottomed out at about 16′ to 18′ below grade, right where GeoTest predicted. Simplistically speaking, these 8 two inch diameter pins furnished the new concrete piers the necessary support so that our new piers wouldn’t slip ‘n slide at all. Done.Each new pier block required two 2″ diameter pin piles roto-hammered into the earth until they each pin could support a 5,400 pound load. Check out the image of the hammering device necessary to drive these pins that deep into the ground! Noisy, slow-going… but they did the trick… without having to deconstruct and rebuild the rock retaining wall adjacent to our work.
Here are some images of the new piers we created. Look closely inside the box in the first photo and you can see the top of the pin piles. They look more like pipe or conduit than something you might refer to as a ‘pin’.
Once our work was completed our clients hired a landscape contractor – A-1 Landscape [no relation to us!] — in order to do the plantings and slope stabilization required to close out their permit.
All is well now! Sadly, this needed repair could have been prevented by the proper attention to detail by the original builder. Concrete work is only as stable as the compaction and stability of what its built upon, but the original builder blew it.
Whatcom County’s property preservation specialists came to the rescue yet again! Here’s the finished project just prior to A-1 Landscape taking over to stabilize the slope and beautify the landscaping.
To round out your education, check out this video of the pin installation process. When do we know its time to stop pounding the pin into the ground? That’s a structural engineer’s calculation. When the pin sinking slows down to ‘X’ inches per second, we stop. That rate of depression shows us that we’ve achieved the proper bearing strength for the pin.