Soil conditions and how they can affect your budget!

Hello everyone from beautiful Costa Rica! Here we are on our second week of work, full with advances. This post in particular might interest you, since we are going to talk about the particular situation with foundations we encountered this week.

Clay like soil type over hummus layer (darker one)

As you can see in the picture there are 2 types of soil at our construction location. Why does this happens? Well, my client decided 2 years ago to fill his lot with more earth to increase the lot’s level. That I was not informed.This is a very common practice, not one I recommend . This lot has a great view to the Central Valley, so he thought that by filling the land he would get more advantage of those views. What this caused is a variation on our foundations and luckily a small redesign for the foundation board. We will also need some additional retention walls on sides west and south of the lot, since the weight of the house was not contemplated from the beginning, when this earth movement was generated. I suggested to have a tire retention wall, to reduce that cost that was not included.
When you plan to do any big earth movement in your lot, is better to get some professional advice.


Actual level of foundation boards.
With the help of the soil tests, our structural engineer and my commonsensical thoughts, we decided to bring our foundations to a more superficial level. They were designed as deeper foundations: up to 1 meter. But this hummus layer will make us go deeper than that, ( maybe 2 meters or more) ending up in a costly unnecesary foundation.Our decision was to go only 60 centimeters deep from soil level, with a wider trail of 75 ctms.( it used to be 40 ctms). This is necessary to give the house the right structural conditions for the present soil conditions, and more stability.
Excavation work.
Now it is time to excavate at the correct level, trying not to move our nylon lines. After a proper compaction, in this case done by hand, not with a machine because of  budget limitations, we will have a 35 centimeters ballast base ( commonly is less than this), then we will pour  a 10 centimeter  quality concrete ( usually you use poor concrete), then we will locate our armors, and then fill with concrete again up to 20 centimeters, as shown in the picture.
Foundation detail written down in the Construction Book.
I wrote down all these details at our “bitacora” which is our very important notebook that keeps track of every construction phases going on. Without this book filled by a licensed architect in Costa Rica, you’re not able to build. Municipality and CFIA always check that  it has professional annotations, meaning it is been supervised by an approved professional.

Common “canasta” for foundations, resisting a 2 story metal structure.
With our foundations’ level defined, this is how armors look like, we call it here ” canastas”. All the steel needed has been approved. The place where we bought it is a trustful source, given us the desired quality. We buy materials at a close ” Lagar  Store” .They have sold quality materials over years. These ” canastas” has also been prepared in advance by one man following distances and quantities indicated by our structural engineer. All hoops are rods #3 ( according to Costa Rica Seismic Code) and rods in corners are #4’s.
Foundation material presentation.
With our foundation poured, the next step is to locate one line of block, and the metal plates that will serve as a basement for metal columns. They have #5’s welded to it. These are curved rods that get into the ” canasta”, before pouring the concrete.
Decore block presentation.
We also need to get ready the bathroom’s module, that goes all in  decor block up to the second floor. Here we are calculating the correct block distances and locations,in order to work with a module and don’t have any waste. It has been designed like this, now it is been tested. I designed this bathroom module all made out of block for 2 reasons: one for structural stability give to the rest of the house structure, and second to have a thick protected wall resistive to rain, moisture and wind. It is located in the northeast section of the house, meaning that this wall will receive the biggest amounts of rain. Northeast is an important facade in the Central Valley, that needs to have special attention.
With our foundations poured this week, then we can move on to  the most interesting part of the project:metal work.
It is a pleasure to be sharing this information, any questions please submit the form below..
Until next time!
Gloriana







 

 

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