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blanning 07-31-2012 07:06 PM

Hello and some pier foundation questions
Hello everyone. My name is Brian. I'm an american living on a farm in rural Uruguay.

I'm planning to construct a few small buildings to add to the ones already here. I'm handy and have done a lot of smaller projects like basements finishing, plumbing, and electrical. But concrete is something I haven't worked with before. I figured I'd start with a small square workshop building, and if that is a success, I'll try to build a larger house.

I did a few searches here and answered some of my questions. But I wanted to go over the procedure for putting in foundation and getting to a first floor deck. Please have a look and see if you can add anything or if I'm completely nuts.

Here's what I think is the right procedure:

Use a tractor with a post hole digger to drill holes for concrete piers. I'm not sure what diameter to use, but I'm thinking 8". (I think my auger is 12" though) I'd go down to the maximum depth that the post hole digger can go which looks to be maybe 32". There's never a hard freeze here so there's really no frost line. The soil is black dirt 12" down with clay below that.

I'll put maybe 4" of gravel in the bottom of the hole and wire up some rebar to set into the hole.

I probably can't find sonotubes here so I'll make some sort of round form out of whatever I can find and maybe have the piers extend 12" out of the ground, probably some kind of plastic pvc pipe or something. I won't use a form for the underground parts of the piers, just rely on the walls of the hole.

I'll set a j-bolt into the top of the wet concrete and later use that to bolt down some as-yet unknown metal bracket.

I'll use one of those small concrete mixers to mix concrete a bag at a time. Is it ok to pour half a pier and pour the rest the next day after the first half has started to set?

I'll try to find some sort of pressure treated beam or glue lam to act as a sort of rim joist around the perimiter, then use metal joist hangers (If i can find them) and run joists to make a sub floor. I'll insulate with something between the joists and probably use OSB as decking.

Is 6' apart too close to too far for the piers? Do I need just the perimiter or do I need piers in the middle also?

For a 1 story structure, what size beam should I use? Two 2x8s sistered together all the way around with 2x8 joists? Or should I use 2x10 or 2x12? How far apart for joists? 12" on center? This is going to be a wood shop so I'd probably like to over-do the floor a little.

Outside of the capital where I am, there are no building codes and no permits are needed. So I'm free to get it right or get it wrong and no one will care.

Maybe what I need is a website or something explaining the process.



Daniel Holzman 07-31-2012 07:40 PM

You have no building codes, no inspections, and no instructions. I would start by purchasing a book on home construction. There are many ways to build the foundation for a house, it might be a very good idea if you make a point of checking out local construction procedures to see how it is done down there. No point trying to force foreign construction practices onto Uruguay, yours is surely not the first house to be constructed, check out other successfully built houses, ask how they were built, who built them.

Foundation design depends a lot on locally available materials, local practices that have evolved, and local soil conditions. Best to do careful, thorough research first, and bear in mind that seismic issues may be important in your area.

blanning 07-31-2012 08:06 PM

Thanks for the response. Although I wasn't clear in the original post, I've sort of already done what you suggest. Houses here are not really built to what most would consider a safe building standard. There's also no set or customary building technique here that all of the house builders use, like we have in the US.

The house I'm currently living in for example, has a "chapas" roof, which is just galvanized corrugated steel. That's it. No insulation at all. There are wood ceilings in some of the rooms, and the air space acts as a sort of insulation. But it's entirely inadequate. I have plans to spray expanding foam polyeruethane insulation in about a month.

To give you more of an idea, it's not uncommon here for a builder to pour some sort of foundation, then a slab, then pour steel reinforced columns in the corners and every 6 feet apart, then put a masonry roof on the posts, then come back and fill in the walls with cinder blocks. In other words, cinder blocks here are for filling in voids, not for bearing loads. And a builder might use a mixture of cinder blocks and hand-formed red bricks depending on the situation.

In paraguay, it's worse. People intentionally leave rebar hanging out of posts because you don't have to pay taxes on a house thats "unfinished". So people try to not finish them in creative ways.

Insulation is rarely used here because it's expensive and hard to find. Power tools are rarely used because of their cost also. Small cement mixers are common. But something like a compressor and air hammer for demolition on existing concrete or cinderblock walls would rarely be used. They use a chisel and 2lb sledge. Most things are done by hand. Tools are expensive. Labor is cheap.

I belong to a group of expats here who have concluded that the building standards here are simply behind and unacceptable. So we're looking for ways to replicate here what we would consider standard building practices in the US. They're just now starting to get building materials that are common-place in the US.

Having a house built here using things like steel studs, drywall, OSB, hot water run to every faucet, insulation, central air, house wrap, wiring and plumbing entirely inside the walls... all normal stuff, are considered luxury items. They would call this an "american" home. You'll pay a premium for it. Finding a contractor who could execute it correctly would be highly problematic. It would take four times longer than we would expect. And it would cost several times more than we would expect.

So a lot of people here keep right on building the same old way and have all kinds of mold and condensation problems to show for it. Substandard foundations are everywhere, which you can see from the cracks in walls from settling problems. They also don't care about drafty windows and doors because they consider an air-tight house to be unhealthy. Really old houses are even designed to allow rain water to just flow through the house... goes in one door in a bedroom and runs out the front door. They put little channels in the concrete thresholds to allow water to escape. You have to step over the creek running through your livingroom. :laughing:

We replaced all the windows in our current (60yo) house with aluminum windows. They're single pane though. The old ones were original and look like they were welded up with steel angle iron and painted. No screens.

We also have a 100yo house on the property. We won't be renovating that one since it would be cheaper to build a new one. That has 4" thick mud walls that were plastered over and painted. The lath in the walls was made from woven tree branches. The entire wall is peeling away from the hand-formed-brick walls now.

Fun stuff. So in short, there ain't no good standard techniques here. :laughing: And anything resembling normal in the US would be a vast improvement.

Edit: oh, no earthquakes here ever. And no tornados or hurricanes either. And it never snows more than flurries, so no snow loads. If there are any problems here, it's probably that the environment is too wet, and maybe occasional insect problems.


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