Footers and Mud Slabs.

I have mentioned soil compaction before, in connection with foundations for general construction. I will touch on it again because it is important. There are a lot of rules about compaction; the idea is you don't want whatever you are building to fall down, droop, sag, crack or otherwise become unsafe or hazardous. You can build a great structure with all the best workmanship and materials but if the foundation isn't any good, you've wasted your time and money. I am an advocate of building codes but I don't believe general rules should be applied without understanding the principles involved. This is where I get in trouble with engineers and building officials - their applying of general rules without understanding the mechanics. There is no place on earth where that is more prevalent than Ecuador. They have no clue except to apply general rules - no ifs, ands, or buts about it. I am getting away from the point -- that being a good solid foundation for building.

The International Building Code for Earthquake Resistant Housing is the prevalent code here in the Sierra region of Ecuador and it calls for excavation of 3 feet and backfilling with suitable material to grade. Now this is for a one or two story single family dwelling. Folks around here have been building houses set right on top of the ground for hundreds of years. There is an old adobe house on my property in La Paz that has been there for at least 150 years and the walls are still standing even without a roof since the last generation lived there. The point is that sometimes it is better not to do anything rather than monkey with something you know nothing about. Nuclear and Proctor density tests for soil compaction are not practical for most home sites and will cause a lot more problems than just digging a footer (to below frost levels), drop some gravel, put in your steel and pour the footer. The general rule for width and depth of concrete are, twice the width of the foundation and 8 inches thick for blocks, 12 inches for a poured stem wall. Two #4 rebars with cross ties every 12 to 16 inches. I used to carry around a pocket penetrometer when I put in footers and have only found a few instances where compaction was less than a ton per square foot when you skin the trench. If you dig past the footer level and backfill, you have problems. I get a little nuts about foundations because I have seen some real disasters masked by soil tests and professional recommendations. I certainly won't build on an iffy foundation.

The soil in La Paz is very tight after you get past the first few inches of high levels of organic matter - which is why they can get away with pouring a slab right on top of the ground. By my estimation at this level the soil will bear an easy 2000lbs. per square foot. My footers will be 12 inches below this level, to a point where the soil changes to a higher clay content and about 2500lbs per square foot carrying capacity - 10 times the load I will be putting on it - I'll be able to sleep at night.

That was a long piece with no pictures. Did I ever mention I was old, hardheaded and opinionated ?