Virginia Northern Neck
--- Footers ---
On 20 and 21 February, our builder, Chris Flora, and his crew -- Chris's
brother-in-law John and a gentleman named Carlos -- prepared the footers for the
First -- if you aren't familiar with the term "footers" -- the footers are
the bottom of the foundation; the foundation of the house rests on the footers.
Our house is using monolithic poured continuous concrete footers.
- Monolithic poured: One footer for which the concrete is
poured all at the same time.
- Continuous: No breaks. The footers are
continuous throughout the foundation.
Footers are wider than the foundation and, for a single-story house such as
ours, are around 18 inches thick. The house sits on the foundation which
sits on the footers which sit on the ground. Thus, it is important to put
the footers deep enough so they are poured into undisturbed, solid soil that can
support the weight of the house. If footers are poured into disturbed or
shifting soil, the house will settle into the ground with terrible consequences.
By using a monolithic poured continuous footer, we ensure that our house has the
best possible foundation.
The photos will explain more.
This is the house site. You will recall from previous photos that the
topsoil was removed and the house footprint was covered with 6 inches of sand.
The house plans contain a foundation plan. Where there are walls in the
house, or load-bearing floor beams, there must be a foundation wall to support
the load of the house and roof. Using the foundation plan as a guide,
Chris laid out where each foundation wall is to be placed -- he did this using
careful measurements of lengths and angles. When he had each wall laid
out, he spray painted it with ground marking paint -- that's the red lines you
see painted on the ground. He then used a backhoe with a narrow bucket to
dig the footers.
It is critical that the bottom of the footers be level all
around the house -- because -- if the footers are not level, the thickness of
the concrete will vary, resulting in weakened footers that can crack and cause
the foundation to fail. This is how Chris keeps the footers level with
each around the house:
The yellow device on the tripod is a laser projector.
It projects a thin laser beam across the house site. This device has a
bright red laser that projects into a mirror that is spinning at high speed
-- similar to the revolving light in a lighthouse -- thereby projecting a
thin laser beam all around the site.
The white pole leaning in one footer has attached to
it a laser detector. This detector is attached to the pole at the
Then, the backhoe operator digs a shallow trench.
The pole is set in the trench and the person with the pole checks to see
where the laser beam is striking the pole. This tells him how deep the
footer is. They keep digging a little at a time until the laser beam
strikes the laser detector -- which beeps -- then they know the footer is
the proper depth.
Then, they move the pole along the length of the
trench, checking for high or low spots.
This way, the bottoms of the footers are all level
with each other.
After all footers are dug and any loose dirt left from digging
is removed, steel reinforcing rods -- commonly called "rebar" -- are laid
in the trench. When concrete is poured into the trench, the rebar provides
a continuous ribbon of steel to hold the concrete together as one piece --
HOWEVER -- note that the rebar is lying on the ground.
After rebar is laid into the trenches, it must be set onto cradles and tied with
wire. The cradle is a formed piece of wire on which the rebar rods are
laid and then tied in place with a short piece of wire. The following
photo shows tied rebar up close.
In this photo, you can see the rebar elevated on cradles
and tied together with tie wire. Note that the rebar is tied to the
cradle, and, pieces of rebar are tied together where they join. Note also
the guide pin. This is a piece of rebar driven vertically into the
ground. Using the sight pole and laser level, these pins are aligned so
that their tops are all level with each other. Then, the concrete is
poured to the top of the guide pin, resulting in a level footer with even
thickness throughout the foundation.
GO TO THE NEXT PAGE FOR
MORE PHOTOS OF THE FOOTERS.