Thursday, June 14, 2012

Une Petite Maison - Concrete Pour

I'm a few weeks behind but wanted to post some photos of the concrete pour.  There are some mistakes in residential construction that are relatively easy to fix... concrete, not so easy.  So I was a little bit worried.  The concrete subcontractor had the forms up quickly for the laundry room addition, but I noticed it seemed a little small.  Yep, 9'x6' instead of 9'x9'.  They had to dig another beam trench and reset the rebar.

Once that was corrected, they formed up the front porch extension.  I checked the dimensions the evening before the concrete pour and-- oops-- 2' too long.  Fortunately they were able to correct that before the concrete truck showed up the next day.  Once the truck arrived, it sat across the street for a few minutes, growing a "tail"...

When the chute was sufficiently long, the truck backed up the driveway as the concrete crew used a 2x8 to lift branches out of the way.  Once the truck was in place, they directed the chute over the porch formwork.

Then the driver let 'er rip, and the mix started to fill the formwork as the workers aided the flow over the rebar and compacted it.

I went upstairs for a bird's-eye view...

After the porch was done, the truck backed up a little more to access the laundry room formwork.  It didn't take long to complete the pour, after which the workers spent some time smoothing it out with steel trowels.  I had spent some time earlier laying out the anchor bolt placement and marking it on the formwork-- the anchor bolts are J-shaped bolts that get placed in the concrete with about 2" sticking up from the top of the slab.  Once the slab cures, the sole plate (framing bottom plate) is marked for the bolt locations, drilled, and placed over the bolts.  Washers and nuts tighten the plate down to the slab.

This was more of a concern though.  The photo above shows the T-shaped steel plates I designed to connect the porch posts (Douglas fir 8x8s) to the concrete porch.  Two of the plates were expansion bolted into the existing porch, but the other two had to be set in the right location.  Fortunately I was there because the concrete contractor initially set them rotated 90 degrees, a mistake that I caught and corrected right away.  The next step was to notch the columns, which the framers did with an electric chain saw.  Then the columns were slipped over the steel plates and through-bolted (the plates were pre-drilled).  

It ought to hold up just fine-- the columns sit about 2" above the porch to minimize potential damage from rot.  Each plate weighs about 20 pounds and is welded out of 1/2" steel plate.  Next up, more framing, windows and roofing...