What is the geology of the site for: two examples from an experienced engineer

Are geotechnical surveys required at the site? Is it worth overpaying for a bunch of unnecessary papers if a neighbor has a house and everything is fine? These are the questions that arise for everyone who starts building their own house. FORUMHOUSE participant Artyom Polorchyan answered these questions and provided photos from the objects when the geology was taken, but the customer did not take it seriously.

How much does the geology of the site cost and can you do without it?

The cost of geology sometimes reaches 15-30% of the cost of the foundation, and here a person thinks: “Why pay for geology, if you can play it safe and lay more reinforcement, make it thicker, wider, deeper foundation?". Unfortunately, this is not a panacea.

Of course, difficult geological conditions are not encountered so often, but they do occur, and for some reason every customer is sure that he has just the most common soils. When asked if there is geology, most of the customers answered: "Nothing special, fertile layer, and then loam with soils, everything is fine." However, loams, like all types of other soils, have very different characteristics from each other, which can be determined in the field "by taste and color" or by rolling and other techniques impossible. Any 1st year student of the Faculty of Civil Engineering will tell you this.

Example 1

Three years ago, a customer from Krasnodar Territory, Art. Novotitarovskaya. There is no geology, but according to the experience of neighbors, everyone makes an ordinary tape, with a depth of 0.8 m (freezing depth in the Krasnodar Territory) under the responsibility of the customer. So it was accepted in the project. In the process of developing the project, there were a lot of options for the layout of the wall and roof pie. The client liked my work and experience, so he asked me to organize the entire construction process of these objects, from the preparation of the site to the vertical layout of the site.

A strip foundation was laid with a depth of 0.8 m, floors on the ground, KBB walls with insulation and cladding brick (a three-layer wall, in my opinion, is not the most successful solution, but the customer insisted despite all minuses). Now they live in one house, finishing work is being completed in the second. The flight is normal!

Example 2

And literally now, a customer has appeared from the same village with geology, according to which there is a layer of bulk soil with a thickness of 2-2.5 m on the site, where foundations cannot be planted. That is, geology in this case will help you choose the right type of foundation. Yes, perhaps, if you make a slab foundation and the house itself is a small one-story frame, then everything will be fine. And perhaps, in 10-15 years, uneven precipitation will appear, which will not be critical for the frame. But problems may appear after the first winter, which can be eliminated (to strengthen the foundation), but the cost of such events, in my experience, will be several times higher than the cost of the house. And if the house, which the customer plans to build from aerated concrete, with a monolithic reinforced concrete floor and two full-fledged floors, plus a roof made of natural tiles, then I think in such soils on a tape with a depth of 0.8 m there will be Problems. This difference in characteristics of the site is associated with the distance from the existing river.

And in my experience there are a lot of such stories, when the customer is sure that everything is fine with the soil, and problems arise during the development of the pit.

Conclusion

With this story, I am not urging everyone to do geology without fail. I believe that if the house is simple, then you can use the experience of neighbors whose house is located a short distance from your site.

Before buying a site, you need to find out: what is the geological situation in this place; what about groundwater; what foundations are used for the type of house that you plan to build on the site. Perhaps the neighbors are making frame frames on screw piles, and you are planning a stone house with 3 floors. From my own experience, I can say that there are such geologies that, due to the complexity, the cost of the foundation is very high and it might be worth giving up buying such plots. But there are no unsolvable problems - a house can be built on any soil, it's only a matter of cost.

How do you inspect a site before construction? Suggest alternative methods.

Agree with Artyom - like it! If you think that you can do without geology - write in the comments.

Read also: subtleties of choice and secrets of facing brick laying; method of protecting a well from melt water. Watch the video: how to organize an efficient water supply at any depth.