Basement Retrofit

In our October post, we uploaded a bunch of different pictures from that month, including this one:

You might have asked yourself, "Why is Natasha drilling holes in her foundation?" Well, when the next big earthquake hits, we're hoping to avoid the fate of the house on the left:

We won't know if we succeeded until that fateful day, but here's a quick primer on how we did our best to retrofit our house to withstand seismic activity.

The first step, as illustrated above, is drilling holes in the foundation. Well, really, the first step is to get your dad to help -- because father knows best. (So much so that he may have to set us straight on some of the specifications in the comments section; the details are already starting to feel hazy and may be slightly incorrect as listed here). This work never would have gotten done if it weren't for the one and only Bob MacDonald, so we again thank him profusely for all his help and hard work. You're the best, Dad!

At the Berkeley tool library, Dad rented us a heavy-duty drill, which we used to make some ten or so holes at strategic locations around the foundation, primarily near the corners. Drilled through the wooden sill plate and the concrete foundation underneath, the holes were seven to nine inches deep, maybe 1/2 to 3/4 inches in diameter. Once we'd had those drilled, we cleaned up the site with a vacuum and then a wire brush:

After that, Dad readied a double-barrel caulk gun to mix some ultra-strong epoxy for injection into the holes:

The disposable nozzle mixes the epoxy before it comes out:


Once we injected the epoxy, it was time to insert metal bolts. You have to act quickly, before the epoxy starts to dry:

Wiping off the extra epoxy:

Voilà!

Take note of the lighter piece of wood lying horizontally on the other side of the stud (the stud is the darker, vertical piece of wood). That will be important later.

Once the metal bolt is secured, it can be fitted with a bracket:
Secured with a nut:Screwed into the stud:



And now the foundation is more solidly attached to the studs. With these brackets in place, our house should be less likely to pop off of its foundation.

Notice again the horizontal piece of wood on the opposite side of the stud. This is called blocking, which is integral to the next step, which is putting up sheer panels.

Sheer panels (plywood of 1/2 or 3/4 inch thickness) get installed in corners, extending out eight feet if possible. The panels get nailed into the studs to prevent lateral movement during an earthquake (unlike the brackets, which oppose up-and-down movement). In our house, there is nothing to nail the sheer panels to on the bottom, which is why the blocking (2x4s, cut to length) is necessary. Blocking needs three or four nails per segment, while sheer panels get a nail every four to six inches along the studs and blocking. That's somewhere in the neighborhood of 50 nails per panel -- a lot of hammering.

Once the panels are up, you need to drill holes in them, so that any moisture that makes it into the space between the panels, studs, and siding can escape:

Finally, after months of hard work, our basement retrofit was finished this past weekend. Here is what it looks like: