Good afternoon, dear guests and subscribers of the "Build for myself" channel!
Why is the topic of a porch or an extension to a house so exciting? The fact is that 50% of all extensions to houses are performed after the construction of the main structure and half of them are performed incorrectly, therefore, often you have to see how between two different structures located on different foundations a crack appears, which over time - increases.
Why is the crack opening?
The whole reason lies in the foundation. The structures are "dispersed" for the following two reasons:
- due to the difference in the depths of the foundations - the load falls on different soil layers;
- inconsistency of loads on the base (on the ground) between the two structures. The shrinkage of the first structure is stronger than the second.
I constantly hear from builders "AND! Porch? We will do this quickly. We'll dig out half a meter and fill it with a tape or a slab - that's what they've always done! "
Friends, why not build a house as well ...
I would like to immediately refer to the primary source - to the basis of the foundations of construction - to building codes and regulations in which there is no document, which would separate the foundations into the foundations of houses, foundations of outbuildings, foundations of porches, foundations of sheds, foundations of toilets and other. There is one single standard: "Foundations and foundations". Everything! All foundations must comply with one single requirement - to transfer the load from the house to the ground so as to keep the erected structure intact and safe for many years.
As in the case of my article with fences: there are no separate foundations for heavy fences and separately for light fences - there is one single standard and requirements are the same for the whole variety of designs (If you are interested, the article is available at link: Foundations for fences made of mesh-netting, profiled sheet, wood and other light materials)
Now on the topic: is there a need to tie the porch foundation to the main foundation of the house? Yes! Only the anchoring of the two foundations must be performed correctly, otherwise a year, two, five years (depending on the type of soil) - and they will disperse among themselves!
You can of course argue that the load on the house and the load on the porch are radically different! It is true, but the load acting on the structure and the load transmitted to the ground are TWO ABSOLUTELY DIFFERENT THINGS, which are regulated by the foundation.
The load from the house on the foundation can be 100 kg. per 1 sq.m., and the load from the porch can be 10 kg. per 1 sq.m., but in these two cases we can transfer the load to the base (to the ground) - the same!!! Those. soil is loaded the same, therefore shrinkage will be is the same. This is the whole point of building a foundation based on the foundation underneath! Therefore, the standard is named so "Foundations and Foundations"! And in this case, two adjacent structures will never part, and even more so the porch will not sink or rise from the frost! The calculation of the pressure on the ground is made by calculating the support area of the foundation, which depends on the bearing capacity of the soil.
In other words, the higher the load, the larger the bearing area, and the lower, the smaller the bearing area of the lower part of the foundation on the ground.
And it doesn't matter at all whether the foundations are different or not, the house can stand on a tape, and the porch on a stove, or vice versa, or maybe an extension to stand both on poles and on piles - the rule remains the same: keep the same pressure on the base, i.e. to our priming.
The only caveat is that the porch is never made on a shallow foundation, as there is a very large the probability of freezing of the base under it due to the impossibility of ensuring the preservation of heat, in contrast to the heated houses.
How is an add-on structure anchored?
In all cases of anchoring, the reinforcement is the reinforcement. All methods require an expansion joint.
The simplest way: a part of the existing foundation is knocked out with a puncher to the first longitudinal reinforcement. Further, the reinforcement of the foundation of the extension is bent with a hook and starts behind the reinforcement of the foundation of the main structure, the frame of the porch is knitted and everything is concreted at once (illustration below).
The second option: We drill holes in the foundation with a size of 3 reinforcement diameters and wedge the reinforcement in them using a mortar on self-expanding cement. I described this method in great detail in the article "Concrete porch without foundation ". For better adhesion, you can use oblique borers under 20-30 degrees.
That's all. I really hope that the article was useful to you.
Thanks for attention!
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