WK 10C: Final Foundations

Yes, that's a cement truck, a city garbage truck , AND a concrete pumping rig all elbowing for the same space.
So I’ve left a lot out over the past couple of posts so it’s probably surprising to see the progress. Over the past three weeks we’ve poured grade beams for the upper foundations, built the lower masonry walls, installed pipe and gravel for drainage around the lower foundations, backfilled the lower walls, and begun construction on the upper masonry walls of the first level of the house. So to use the parlance of the trades, we’re “out of the ground”. It took a lot of effort to get here and there is still a lot to be done before the end of the foundation phase.

I’m going to be shutting the job down for a month while I go to Berlin to teach Design Studio on behalf of Woodbury University here in L.A. Upon my return in August, we’ll crank things up again and start the final phase of the masonry/foundations.

This is the state of the work as of the 3^rd of June. You can see that only the cages for the grade beams or the foundation of the building are in place.

This photo was taken on the 27^th of June. Our foundations are all poured, and the first “lift” of the wall is built. The slab area for the first level is backfilled and ready to go, and the building is starting to take shape.

Week 8C: Concrete 101 pt.2

Before “grout filling” the wall HD (hold-down) hardware must be inserted at particular locations in order to provide resistance against stresses exerted on the building by earthquakes and wind. The hold-down literally holds the building to the foundation and in quake-prone SoCal the hardware required can sometimes be very large. At the lowest level of the project, we have HD25’s which are about 1.25” inches in diameter. The positioning of these HD’s is critical as one has to account for the correct spacing off the face of the building and the thickness of the column the HD will be bolted to.
The whole process is made even more difficult by the fact that the wall these HD’s are going into is 9’-0” tall and the HD’s must be positioned at the base and inside of the wall. In order to mark the HD locations careful measurements must be made to account for the precise locations and then the threaded rod which is one part of the HD’s is inserted into the cell. As you can see from the image, it has a 1/4 steel plate on the base which grips the concrete and prevents the rod from being ripped out of the cell.
Later, during the framing phase the rod is connected to a steel angle which bolts directly to a column. More on this later.

Week 8C: Concrete 101

This week we poured and built the lower retaining wall of the house. Since the project sits on a hillside, we needed to create a pad for the lowest floor. Things are moving along now and we’re on schedule for finishing up the foundations prior to my departure to Berlin. The photo above illustrates how difficult it is to stage work on the site. Garcia Masonry has built a deck for their supplies in order to make staging easier.

The grout must be tested to ensure that the concrete in the masonry walls is of the appropriate strength (2500 psi). It’s rare that the concrete would come in under it’s required strength, but occasionally site conditions, too much moisture, and fluctuations in temperature cause the concrete to cure unevenly. During the pour, Shorty, our concrete pump operator fills the test cans and boxes for the deputy so that we have accurate samples coming straight out of the truck.
Because the concrete for the grade beams is 3000 psi we are required to have it tested to ensure it reaches it’s maximum strength. Test cylinders are cast and then allowed to cure for the maximum 28 days. They are then taken to a lab and put through a pressure test to see if the concrete holds up.

Week 7C-8C: Grade beams phase 1

We’ve had several coordination issues on the job because of the hillside. The one we’re dealing with this week has to do with the downward slope retaining wall which was originally designed to retain 6’-0” of dirt. Unfortunately, the hillside forms a bowl in the middle which caused our retained height to skyrocket up to 9’-0”. A revision called a structural bulletin was issued and stamped by the engineer. This is basically a field revision that one gives to the city inspector to show that the engineer has examined the condition and has revised the original structural drawings to incorporate the change. This change is also noted on the structural observation form that the engineer signs when they inspect the work prior to the pouring of concrete.

Last week we had some slow-downs due to the availability of rebar but the week ended with the crews up to their armpits in steel and dirt. We’re on a tight schedule now since I’m leaving for Berlin at the end of the month to teach, so there is no room for error or delays. The week started out with some frantic calls to our plumber. A kink in the schedule had placed him towards the middle of this week, then by Saturday Garcia Masonry made it clear that their work was going to be ahead of schedule and we’d be ready for inspection on Tuesday. Always looking to make up time I lined up our inspections with the hope that everything would fall into place at the last minute.

Several phone calls later I finally managed to get the plumber (who was tied up on a job in the Palisades, an area with notoriously bad phone reception) on the line. Armen Sargsian, of AS Plumbing got his guys out to the job just in the nick of time, and at the time of this missive it assumed that all of our work is ready for inspection by the Deputy Inspector, and Christian Williamson of CTW Engineers.

Guess how big the steel is? The easy way to figure it out is multiply 1/8” (# of the steel). We are using #10 rebar for our grade beams which means that the rebar in this picture is 1-1/4”- about the size of a closet clothes bar.