Jack on Jack
Fig. A: Level the sand subfloor. Fig. B: Choose a pattern
that fits your style. Fig. C: Lay each brick, fitting it
tightly against the others and leveling in all directions.
Fig. D: Continue your pattern throughout the room,
and the walls — with concrete. This doesn’t use
much concrete, and can be done in half an hour. Mix
your concrete with screened sand, and then trowel it
smooth and level with the tops of the bricks. Do this
along the entire perimeter of your floor, and then let
the concrete dry completely (Figure D).
7. Fill the cracks with sand.
After your concrete perimeter is dry, sweep fine sand
into all the cracks between your bricks (Figure E).
Allow the floor to settle for a couple of days, and
then sweep more sand into the cracks. Repeat this
several times until the sand no longer settles.
8. Seal the floor.
To seal the bricks so that you can sweep and mop
them, use an acrylic or oil-based concrete sealer
or varnish. Until you’ve sealed them, the bricks will
be coated in a fine dust as you gradually wear them
down; this is OK for a patio or outdoor floor, but it’s
not as acceptable indoors.
Use a roller to spread the sealer, and a brush to
coat any cracks that the roller can’t penetrate. Give
it at least 2 coats. The difficulty in sealing arises
from the sand in the cracks where the bricks join. As
you roll the varnish on, the roller picks up sand and
lay edge bricks, and fill the perimeter with concrete.
Fig. E: Sweep fine sand into gaps between the bricks
to provide a tight fit. Fig. F: Finish the floor with a nice,
spreads it over the bricks. To avoid this problem, wet
the sand down beforehand and use a sealer that’s
not compromised by moisture (many concrete
sealers are designed to help cure concrete, meaning
that they trap the moisture inside and allow the
concrete to dry more slowly).
NOTE: The sealer will darken the natural color
of the bricks (Figure F).
Most concrete sealers and varnishes have a strong
smell. Always provide adequate ventilation, and plan
to keep those windows open for a few days.
Adobe: Build It Yourself » by Paul Graham
More on CEB floors: »
Open source CEB-making machine: »
Abe Connally and Josie Moores are a young, adventurous
couple living in a secluded off-grid hideaway with their
2-year-old. Their experiments with energy, architecture, and
sustainable systems are documented at