Cement truck poured slab or site mixed footings?

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The ideal foundation is footers, foundation walls and the slab of 3000 PSI poured concrete. Review the guidelines below and let me know if you have any questions or concerns. If you want the most durable concrete construction you can pay the additional money to have premixed concrete delivered to your building site in order to pour a greater PSI mix monolithic foundation. With the consistent seismic activity here, the only sensible solution is to construct a “floating slab”. If I were the owner of a dwelling in this area I would justify the additional expense to construct a suitable foundation to support my concrete slab as inexpensive insurance. Please review the following construction guidelines and try to understand how this “floating slab” provides the stability that is needed in a seismic area like Costa Rica.
GUIDELINES
Excavate 4′ deep trenches where footers are indicated on blueprints.
Provide 2″ x 6″‘s for forms per print.
Set forms for 8″ high and 20″ wide on top of excavated trenches.
Run 2 x #4 steel rods horizontally, equidistant, side by side 4″ from bottom of trench while pouring concrete footers.
Run stickers, using #4 steel rods every 4′ projecting 6″ vertically from top of footer.
Set 48″ poured wall frames block on top of concrete footers with vertical stickers inside of all blocks.
Attach 6′ long #4 steel rods to stickers projecting from wall every 4′, leaving 2′ protruding from top of wall to bend into poured slab.
Pour concrete in all forms or inside all blocks.
Fill inside of walls with fine sand and compress in layers to achieve a solid base and backfill around exterior of footer walls with same or clean topsoil
Compress sand inside of walls several times adding more sand as it is compressed, until top layer of sand is smooth and firm, 4″ from top of walls to accept 4″ of #57 stone following rough-in of plumbing, electric and HVAC tubing.
Dig all column pads and interior footers per blueprint and set forms as above
Run sanitary and water lines 15″ below floor, avoiding pads and interior footers.
Run water line from the tap into the area of the dwelling where the shut off valve will be installed, avoiding driveways and walkways.
Run metal conduit for floor plugs or HVAC pipes per plan.
Set forms around perimeter of footers and foundation walls and then spread #57 stone evenly where slab is to be poured.
Cover stone with minimum 6 mil polyethylene vapor barrier.
Bend #4 steel rods protruding from the top of the footer walls into the floor and connect the steel rod grid system made by attaching additional steel rods to the existing protruding from the footer walls.
Order 3000psi concrete and pump or pour a 4″ solid monolithic slab.

We have now poured concrete into and over a steel grid system that connects the perimeter footings through the foundation walls and into the slab. This floating slab is structurally sound from corner to corner and will not fail from seismic activity or settling.

You should be aware that there are areas where ready-mixed concrete is not available and site-mixed is your only option. That was the case with our main house which our builder, who is based in San Jose, wanted to use ready-mix for but no one would deliver to our site.

You can see our new article about Tom Rosenberger AKA ‘Tomasino’ a Costa Rica Homebuilder at

Scott Oliver – Founder
WeLoveCostaRica.com