Concrete Work - Part 3

The "concrete work" is the making of the footings, the 8" thick stem walls, garage slab, and driveway section associated with my project to extend the garage six feet.  It also includes the slab for the new front porch.  Once the concrete work is done, it's going to sit there waiting for the construction of the garage extension and the front porch roof, which may or may not happen next spring (or who knows when) — but the concrete will be ready!

So the construction of the wooden forms for the concrete went relatively quickly, if not straightforward.  In my past, I've put forms together using special metal rods called "snap ties," which hold the two sides of the forms together at a constant separation, and resist the force of the wet concrete, which tries to push the form walls out (with considerable force).  Snap ties look like this:

Neither Home Depot nor Lowe's carried them, and an internet search turned up no local sources.  I did find out later, however, that a couple of concrete supply companies in the county have them (they apparently just don't have web sites with sophisticated search engines key words).  So I improvised.

The lower trench I dug served as the form for the footings, and I built wooden forms that sat on a wider higher trench for the 24" high stem walls.  Looked like this:

The lower section in the front wall is for the entrance to the garage, that is, where the garage door will go.  To keep the wet concrete from the higher section of the wall flowing out the lower opening, I screwed a section of plywood on top of the opening after the lower section was filled with concrete and leveled.  Here it is, ready to go.

The new walls are tied into the old garage concrete with sections of rebar epoxied into holes drilled into the existing concrete.  I did the same thing with the porch slab. 

The existing garage was built on a slab with no stem wall and no real footings, just a 6" wide by 6" high "curb" on top of the outside edge of the slab.  So there was not much to tie into.

I put half-inch rebar in the forms — two rods running parallel inside the footings, and through the stem wall—one half-way up and two near the top.  The anchor bolts for the bottom plate of the future stud wall were put in place in wooden braces that held the tops of the forms 8" apart:

You can see that I suspended the upper rebar from the wooden braces using nylon string.  That worked, although if I had located the snap ties, I would have wired the rebar to the snap ties for a more solid connection.  File that under — "if I had it to do over again."

The porch slab forms were more straightforward, and much quicker.  They were just three 2x6s held in place with screws and steel stakes.

The future porch roof will be supported by two 4x6" posts at the front corners.  The metal brackets that connect the posts to the slab are anchored by bolts cast into the concrete, and sitting on top of footings reinforced with steel rebar:

I hired a neighbor (who happens to be a concrete maestro) to take charge of the actual concrete pour.  He brought along his son-in-law.  And there was the concrete truck driver, and also the guy with the concrete pumper (concrete run through a big hose that could be more accurately placed inside the 8" wide forms, and could run over to the front porch — otherwise it would be pushing wheelbarrows back and forth).  A big party.  When wet concrete starts flowing, things happen quickly, and the more people on hand, the better.  And that's a fact!

We filled up the footings first, and to give that concrete time to start to firm up (so pressure from concrete above would not force it out around the bottom of the forms), we moved over to the porch.

At that point, things became too hectic for me to take any more photos.  I had calculated that we would need 3.35 cubic yards of concrete, and planned to add another 10% margin, which took the total to about 3.7 cubic yards.  But you can only order concrete in half-yard increments, so we ordered 3.5 cubic yards, and that turned out to be not quite enough.  I ended up hand-mixing three 60-pound bags of concrete to top off the forms.  Another lesson for the "if I had it to do over again" file.  But if everything was not optimal, the job got done, and no disasters.

That was Saturday morning.  I started taking apart the form supports late Sunday, and removed the forms today (Monday).

And the porch:

So the next step is to backfill on both sides of the stem wall, to bring the level of the soil about 4" below the level of the new garage slab extension, and the new driveway directly in front of the extended garage.  And then wire mesh and rebar for the new slab section.  And then more concrete (in about two weeks).

And also back to the kitchen countertop project.  I'll be buying more wood for that tomorrow.