Concrete Work — Part 4

Concrete work is done.  Hooray!

Well, just have to remove the 2x6 forms from the side of the driveway slab, and take the plastic sheet off after a couple more days (don't want the concrete to dry out before its initial cure). 

At the end of the last post, I had removed the forms from the foundation (stem) wall, leaving trenches on both sides of the wall, and big piles of hard chunks of dirt and granular soil.  The trenches needed to be filled in, and the piles of earth needed to be removed, to make the ground flat and level (more or less), roughly 4.5" to 5.5" below where the surface of the new slabs would be. 

Unfortunately, the big chunks of hard soil were mixed in the piles of more granular soil, that could be shoveled into the trenches.  It took a few days of separating out the chunks using a pitchfork, three-tined cultivator, and rake, and hauling them to piles in the back yard.  The granular soil was then added to the low areas (and compacted), and dug out from the high areas.  I also bought ten bags of sand to help with the leveling.  Once that was under control, I started making the new forms, beginning with the simple form at the side of the new driveway where it met the yard.

That was the easy part.  The more challenging form was that separating the level garage slab from the sloping driveway slab, the latter being a half-inch lower at the interface.  I decided that a strong but thin piece of wood solidly attached to the concrete wall was needed.  I ended up using a 3/4" thick piece of hard maple with a dado routed in the top edge to separate the two levels of concrete.  I fastened it to the concrete wall with special concrete bolts (screwed into holes drilled in the concrete), supplemented by construction adhesive. 

The maple will eventually rot, creating an expansion joint that can be filled with sand.  Seemed like a waste of a good piece of maple, but the wood store had a big stack of it and it was on sale.  (bought another piece for my kitchen countertop)

I also glued pieces of expansion joint to the front of the foundation wall that would be used as a guide to level the top of the concrete driveway.  Here's what it looked like with a bit more leveling to do.  I used a long straightedge to measure how big the gap was above the soil, adding or subtracting until arriving at a slab thickness of 4.5 to 5.5".

Then I placed the rebar and steel mesh — a lot in the the new extended garage slab, and little to none in the driveway slab (the rest of the existing driveway had no steel reinforcement).  I drilled into the existing garage slab and epoxied four pieces of rebar into those holes, tying the new and old garage slabs together). 

And then I took a breath, and waited.  Saturday morning arrived to lightly organized chaos.  No time for photos.  The concrete truck arrived 30 minutes early, and my neighbor the concrete maestro had gone off on some errand, but he also showed up as I confided my anxiety to the personable truck driver, who conveyed the idea that all would be just fine.  But my neighbor's son-in-law assistant was still missing.  We forged ahead, I jumping from one task to the next — five things going on at once, concrete flowing out of that long chute, being shoveled and vibrated and shoved into place. 

The assistant arrived and I focused on my task at hand, and then the next.  After awhile, enough concrete had been dispensed, and the truck driver set about cleaning the concrete out of the chute.  I guided where that could go, and then my prime responsibility — that would be writing checks.

The truck left and we continued to work.  The assistant left and I became the new prime assistant.  9:30 a.m. to 3:30 p.m.  Six hours and the job was done.  No break for lunch.  Concrete waits for no man. 

Looked like this:

And this:

The concrete maestro does beautiful work.  I was amazed there had been no disaster.  I took another breath, ate a late lunch, and misted the concrete with water and covered it all with plastic to keep the moisture in until the concrete was cured. 

Done. 

Next project: finish the kitchen countertop.  Then cover the newly poured front porch concrete with quartzite tile.  Then pottery studio cabinets.  Then drawers . . .  Sigh.

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.