Excavation and Footings
On October 30 the heavy equipment arrived to begin the excavation. It was finished on November 5.
Notes regarding the construction camera: I changed the exposure rate several times in an attempt to find the best way to document the process. I ended up with more exposures per minute, a five-second interval. I deleted early morning and late afternoon times when nothing significant was happening in order to shorten the film. I also had to move the camera as excavation continued.
A link to the construction camera footage of the excavation is here:
The footing subcontractor pronounced the excavation a success. The maximum deviation from the desired elevation was less than 1.5 inches.
Once
the excavation was finished it was time for the installation of the FastFoot
forms. The final design of the
foundation included 36” wide footings, 12” deep, on the west side and 30” wide
footings, 12” deep, for the remainder of the foundation. The thicker west footing was required
because there is a stud wall inside the SCIPS wall on that side. We decided to add 6” in width on portions of
the south in order to support the deck; our goal is to support the deck as an
independent structure rather than using the SCIPS wall as a structural member.
Basic
information on the FastFoot system can be found here:
This
video gives an overview of the setup and concrete placement*:
The finished FastFoot fabric, bracing and penetrations before placement of the concrete:
Warning:
Wide angle lenses make straight lines look curved!!
East side from the north
West side from the north
Transition from 36" to 30" footing
Footing penetration detail: radon mitigation
Close-up of Radon mitigation pipe
The pour in process:
Beginning of the pour
Screeding
Final level check
Completed footings:
Center of the south wall
Sanitary line on south side
The
verdict from the subcontractor: once
they have worked their way through the learning curve it will be quicker than
the standard dug footings. Setup takes
some time but it's easier dealing with the rebar when everything is above
ground.
Three notes for future reference if anyone is interested in
using FastFoot:
1.
Stanley, the subcontractor, said that he
originally underestimated the amount of concrete necessary. It bulges out below the bracing (FastFoot's
technical term is apparently "pooching out") so he said that you need
to calculate the concrete needed based on the outside of the 2 x 4 bracing, not
the inside dimensions.
2.
They ran into one problem close to the end, when
the final 2 x 4 (you might know it!) twisted off the bracing. They were able to get everything back level
by using leverage to move it back into place and then adding additional bracing. The FastFoot installation instructions tell
you to use two nails, at different angles, to hold the bracing. He used three: one double-headed scaffold nail and two
ring-shank nails. After talking to Alton
it looks like one nail at the center of the bracing and a hex-head screw at the
top might be a better solution: the screw would be stronger than the nail at preventing twisting and would be easier to remove.
3.
Alton noted that contractors who are interested
in using the FastFoot system on an ongoing basis might want to investigate
metal stakes such as these: http://www.marshallstamping.com/nail_stakes.html They are reusable and penetrate the ground
much easier than wooden stakes.
* In most
cases I have deleted long stretches of inactivity. However, in this case I preserved the
two-hour wait for the concrete truck in order to give a true sense of the day’s
flow.
