The choice of the type of foundation of any structure is determined by local conditions. To say that this construction is the most common, it is impossible. The columnar foundation with the grillage is slightly behind the most commonly used tape belt, but sometimes it is more appropriate to erect it.
Experts from the Finns give priority to the invention of this "mixed" design. A mixed it is called because such a pile foundation also has elements of a tape base. He has his own merits, which also determine the specifics of the application. Suffice it to say that the cost of its construction is about 4 times lower in comparison with the monolith. By the way, there are other names of this design - columnar-tape and columnar-rostvierkovaya.
Features
- Relatively low cost, as the consumption of materials is small.
- Ability to choose them. Such a base is mounted not only from reinforced concrete. Posts are erected from brick, stone, in some cases - even from wood( for example, larch, cedar, oak).
- No basement room. Therefore, the columnar foundation is more suitable for industrial, warehouse or household buildings( for example, sheds, baths).Under residential buildings, he settles down, if another type of foundation is not suitable. For example, water subterranean strata are located close to the surface of the earth. It is clear that in this case, to mount the tape base does not make sense. Although for small cottages this foundation is an excellent option for any soil.
- Simplicity of construction and low labor input.
- Convenience of construction. Do not dig a foundation pit( as for a slab) or a large trench( for a monolithic or prefabricated tape).
- The foundation column, unlike the belt or plate foundation, can be built on terrain with a difficult terrain, even on slopes.
Consider the most durable option - on reinforced concrete poles. But first you need to clarify what a grill is.
These foundations, depending on the location of the pillars relative to each other, are divided into single and bush, and from their installation - on the hanging and "racks", buried or not deepened. They, like tape, are monolithic or prefabricated. This depends on the conditions of further operation, which determines the method of the device grillage.
Let's consider one of the construction options in general terms, since the nuances are determined by local conditions, therefore, for each particular structure, certain structural features of such a basis will be selected.
Before proceeding with the installation, it is necessary to carry out a number of preparatory measures, and first of all, to make calculations. But this is a separate big topic, so let's move directly to the production of works. And we will consider the simplest method of installation.
technology Site preparation
A marking is made around the perimeter of the future structure( read about it here), and then the top layer of the soil is removed( "tape").After that, in the places defined by the project for the installation of poles, pit digs. The depth should exceed the freezing level of the soil in the area, plus 25 - 30 cm in order to make a backfill( the so-called "pillow").
When determining the size of pits, it should be taken into account that the column of estimated dimensions will be mounted in the formwork, and its walls also have their dimensions( board thickness, 1 on each side of the square).In addition, the supporting frame still needs to be installed and then reinforced with spacers.
The last step at this stage is waterproofing the bottom. This must be done for 2 reasons. First, during the pouring of the solution, moisture will not escape into the ground, which can disrupt the process of natural hardening and reduce the strength of the structure. Secondly, the laid material during the operation of the structure will play the role of shut-off insulation, preventing the penetration of moisture from the ground into concrete poles.
Usually use ruberoid, but its service life does not exceed 4 - 5 years. Therefore it is better to work with polyethylene or something like that.
Formwork
As a rule, it is made removable. The cheapest option is to use the "twenty" boards. Of them, they knock down the boxes and install them in pits. Then - the spacers.
Sometimes formwork is not done if the ground in the pit is dry, hard, and it is excavated exactly to the size of the pole. It is enough only its walls and the bottom to lay out with a liquid-impermeable material, and it is possible to fill the solution.
The formwork is removed in 4 to 5 days, when concrete "grabs".
Reinforcement
It is necessary to reinforce the concrete fill. Such skeletons are harvested outside the pit and then lowered into it. Since they are collected from a metal rod, it must be protected from corrosion. In order to avoid direct contact with the liquid, the size of the reinforcing structure is chosen in such a way that, after pouring the concrete, its layer between the walls of the casing( s) and the rods was not less than 5 cm from each side. Even if then somehow the pillar is partially crumbled, the rods are not "bared".
Their connection is made only "viscous".Welding leads to overheating of the metal, which "points" changes its structure and reduces the strength in these places.
It should be noted that vertical bars should be higher than the fill level, since they will be connected to the grillage.
Solution filling
The peculiarity is that it needs to be done "portioned".Each layer must be carefully sealed. To do this, use the same rod, bayonet shovel, if possible - a vibrator. The task is to remove all air that gets into the solution, which forms cavities, which will reduce the strength of the column. The fill was considered in more detail here.
There is such a nuance. You can not fill the formwork piece by piece. For example, half today, and the rest - the next day. The fact is that during the night the loaded concrete partially "grab", and between it and the second half of the filling a seam is formed. In this case, it is not necessary to speak of the strength of a monolith of a structure.
External processing of poles
After dismantling of the formwork, the upper sections of concrete structures are protected by a layer of waterproofing( hydroglass, bitumen and the like), thermal insulation, after which the pits are filled. If the soil is of a puffy type, then it is better not to use this land, but to take, for example, sand of large fractions.
Installation of grillage
It is made either on the ground or above it. Proponents of the second option argue that such a method excludes any impact of soil( as well as moisture) on the grillage.
Further everything, as well as at erection of a tape base: a formwork between columns - "pillow" - waterproofing - reinforcing cage - pouring of concrete.
To raise the grillage, you need to increase the thickness of the sand fill( although there are other options).And if it is mounted on the ground, then it is necessary to excavate shallow trenches, so that the upper edge of the "cushion" is on the ground level. Nothing complicated.
All measures are identical to those described above - sealing the cushion and mortar, the dimensions of the reinforcement assembly. After "grasping" of concrete with a "hanging" grillage, the "pillow" is removed.
Do not forget that the reinforcing frame must be securely connected to the ends of the vertical bars left behind when mounting each pole.
Some rules
- Posts( supports) are mandatory installed in all "nodal" points( intersection or abutment of walls, corners of the structure).
- The optimal distance from the post to the post is from 2.5 to 3.5 m. Its increase can lead to the destruction of the grillage, and the reduction will increase the consumption of building materials( and labor costs).
Practical tips for
- Such foundations are well suited for areas with irregularities that can not be "smoothed out" or it is not practical to do so for some reason. They also settle in areas with a large depth of freezing or high groundwater.
- The prefabricated structure is much easier to erect, and it will take much less time. But if you expect a large load, then mount the foundation-monolith.
- If to equip a fixed formwork made of slabs of penoplex, this design will increase the service life of poles. The material will simultaneously protect both from freezing, and from moisture, and from loads due to systematic soil movements.
- The form variant for the "suspended" grillage is the following. On the perimeter bricks are laid, on which the formwork is installed, but with the bottom( of the boards).Then it is easy to dismantle it.
- Before setting the encapsulated formwork in place( in the pit), it should be well moistened with water. First, then it can easily be removed, since it will not stick to the concrete. Secondly, the boards will not "draw" water from it.
