Advice 1: What a Foundation to do, if it is close ground waters

The groundwater creates a serious problem in the construction of buildings. The installation of the Foundation in their high standard has a number of limitations. Choosing the Foundation of a house under construction in such conditions, taking into account soil type, depth of visit, nature of fluids and the level of soil freezing.
What a Foundation to do, if it is close ground waters


If the water table is high in loam, sand, clay or mixed soils, the Foundation should be constructed at a depth that exceeds the level of soil freezing. This makes the withdrawal of groundwater, this event is considered mandatory in these conditions.

In the case where the depth of soil freezing is less than level with the water, you can not make allowance for soil type, Foundation plan, considering only the load of the building. While carrying out calculations, corrected for groundwater level (GWL) from half a meter to a meter in the direction of increasing the real level. For this reason, the strip foundations are excluded from the possible designs, as its price will be very high, and the erection of a bulky and costly.

In the calculation of foundations on soils with a high groundwater table make allowance for the subsidence of weak soil. If there is a risk of seasonal flooding, it is recommended to erect buildings using monolithic reinforced concrete structures. The pile should be below the level of potential soil erosion.

The technology of construction of the Foundation under high groundwater table

First dig a trench to the depth of the Foundation, then the ground leveled and dried. To do this, the perimeter of the site to dig a ditch with a space of 50 cm, its depth is 30 cm and a width of about 20 cm, the Ditch is designed to accumulate and drain moisture. The Foundation does not pitch in groundwater as high risk of leaching solution and attenuation of the constructed plate.

Then at the construction site, conduct soil compaction and concrete preparation. This layer is required for leveling pad and placement of waterproofing. After drying, it is covered with two layers of roofing material overlap each layer of 10-15 cm of Sand and gravel without using and fixing do, with ordinary bitumen is brought to a working condition.

The Foundation will be located below the groundwater level, therefore, concrete slabs, walls and ceilings must be isolated from moisture. Placing of the roofing material need to extend beyond the screed to protect the slab and make the overlap on the erected walls of the base of the Foundation.

Then mount design of wire mesh products and accessories, it will need to pour the solution. Recommend to create a slab thickness of 15, 20 or 30 see What the plate will be thicker, the better it will keep the Foundation and walls of the building. After standing plate, you can start constructing the Foundation. It is best to use concrete blocks, which form a monolithic structure. Once the work is finished, will only protect the Foundation from groundwater using mastic based on bitumen or film of waterproofing.

Advice 2: How to withdraw the Foundation

To bring the Foundation under "zero" means to make all points of its surface located in the same horizontal plane. Display the Foundation under "zero" should be at the time of casting. As it turns out is easier, faster, and stronger. However, there are cases when this is not done in a timely manner, and therefore it is necessary to align the already "set" the concrete.
How to withdraw the Foundation
You will need
  • - cement;
  • - sand;
  • - fittings;
  • boards for formwork;
  • - construction tools (trowel, shovel, axe, etc.);
  • cord;
  • - hydrolevel any or flexible hose.
The elimination of the basement under "zero" during his fill

Put a marker or chalk in one corner, pour the Foundation on the inside of the formwork, mark the planning surface (the zero point). Using hidrorema determine and mark the same zero point in other corners of the Foundation.
In the absence of hidrorema you can set the zero point at the corners using a regular hose. For this position the ends of the hose in two, we check for angles. Pour the water in, making sure that it was not formed air pockets. Select the edge of one end of the hose exactly at the level of the original zero point.
Raising or lowering the other end until you get to the water in the end established at the level of the edges of the hose (i.e. at the level of the original zero point). Lock the position in which he established the water in the second end of the hose. This position corresponds to the zero point. Mark it on the mold.
Make each corner of the base, two vertical cut in the mold so that they were located in the middle of the Foundation walls, and their low point was on the same level with zero points. If you now pull through the relevant cuts the cord, it will accurately mark the zero level surface of the Foundation.
Pour in the formwork concrete mix to the level of stretched cords. This way your Foundation will be displayed under "zero".
The removal of "under a zero" a ready Foundation

Check hydrorunner or hose the position of all corners of the basement, taking one of them for the original. Do all corners of a digital mark that reflects the position of this corner relative to the origin. (For example, "-50" or "+30" would mean that the angle 50 mm or below 30 mm above the original corner).
Install on top of the base formwork, consisting of two boards, the lower edges of which cover the Foundation of two sides and the top are connected via spacers with a length equal to the thickness of the Foundation.
Mark all angles on the inner side of the formwork of the zero point, to which to pour the Foundation on the basis of the actual position of the corners determined in the previous step. Carrying out this operation, keep in mind that the minimum thickness dosalieva fragment of the base should be at least 30-40 mm Too thin layer of concrete will be fragile. Make cuts in the mold to the lower edge were on level zero (similar to how it was done in step 3).
Install formwork rebar. Prepare a sand-cement mix with a ratio of 1:3 or 1:4. Moisten the surface of the Foundation water and place the mixture into the formwork. The under surface of the zero level check cord stretched out through the cuts.
Determining the zero point with a hose, consider the inertia of the movement of water in the hose. Before locking its position, wait for a while until its level will not be established definitively.
Useful advice
During solidification of the cast layer prevent it drying out, which can happen very quickly due to its small thickness.
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