Good afternoon, dear guests and subscribers of my channel!
A foundation is a building structure designed to evenly distribute (transfer) the load from the superior structure to the base. The base refers to the bearing continental soil.
As we know, the calculation of the foundation is, among other things, the calculation of the area of its supporting part on the base, which depends on the weight of the walls, floor, roof, snow and wind loads and etc. So, if the weight of the house is large, and the bearing capacity of the soil is small, then the designer increases the support area, which is exactly what is expressed by an increase in the width of the lower part (sole) ribbons.
That is why, if the project has already calculated the area of support of the foundation on the ground, it is forbidden to arbitrarily reduce or increase the width of the base of the tape. Otherwise, we will receive uneven ground pressure, which entails uneven settlement of the building, followed by deformation of the entire structure.
But how do you implement an inverted T-shaped foundation on a construction site? It's very simple - in two steps:
First stage:
- excavation of the trench is carried out to the width of the supporting part of the foundation;
- the frame is reinforced and the formwork is installed;
- the lower part of the foundation is concreted;
- time is given to harden the mixture.
Second phase:
- The rest of the foundation (walls) is reinforced;
- formwork is installed;
- the structure is concreted;
- backfilling is performed.
The foundation of my house was calculated in a similar way. Cut from the project:
As you can see, each wall of the house has its own tape width (photo below). Why is that? Because despite the seemingly solid construction of the house, the weight of each wall is different, and it depends on the number of openings in the walls, from the distribution of the load from the floor slabs to the walls, from the roof load and etc.:
As soon as I got my hands on a working project, I asked for advice from a builder friend, whether it is possible to do so that not construct the foundation in two stages, and immediately, tie one reinforcing cage and pour in one step concrete?
It turns out you can. There are small risks, but you can still!
I tell
The excavation of the trench is carried out with trimming the walls at the base of the foundation. It looks like this:
The shape of the trench can be different and it all depends on the type of soil. If it is clay or loam, then such an excavated form will stand for a very long time without collapse. With sandy loam, they make a trapezoid (option B of the figure below), on sands - of course this is impossible, therefore sand is the only soil when such foundations need to be poured in two stages. But, the sands have a very good bearing capacity, so there is a possibility that the foundation of a private house will be, according to the calculation, an ordinary rectangle in cross section.
From the author + photo
If you objectively look at both designs and compare, then option 2 is definitely more profitable:
- unnecessary excavation work is not needed;
- no need for full-height formwork;
- no time is required to wait for the mixture to harden.
Minus one - concrete in the ground! But, the walls of the trench can be easily covered with a film material and then - I see nothing wrong if the formwork is the soil itself.
As for my house, I first dug a flat trench and then tied the reinforcement cages on the ground:
The armature was bent so that the frame had an expansion in the lower part and strictly repeated the shape of the trench.
Before lowering the frames, I made an oblique trimming of the trench walls to the estimated design width. He pulled the film along the walls of the trench, lowered the frames, set the formwork from the level of the site to the height of the foundation from the ground. The next day, the concrete was laid:
This is how the "foundation in the ground" turned out, and most importantly - everything was observed and executed strictly according to the project.
I hope you liked the article and moreover, it became useful to you! I think the method is worth taking note!
Thanks for attention!
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