Foundation shoes are very common construction elements that are of great help when cementing different types of structures, in this article we are going to tell you what a footing is, what it’s construction process is like and the different types of footings. that exists.
What Are Shoes?
Footings are characterized by being shallow foundations that are frequently used in soils that have a high or medium resistance to compression, in most cases in homogeneous soils. Its function is to anchor and transmit the tensions produced by a structure to the ground where it is built. Footings are located at the base of the construction and in many cases can be found as a concrete prism at the bottom of the columns or pillars of the construction.
How are the shoes made?
Footings are used when the structure requires a shallow foundation , generally in soils with clay, conglomerate or rocky characteristics, in places where the slopes of vertical excavations are maintained or that have an adequate slope to provide stability. that it needs, then we are going to tell you about the construction process for the footings.
What should you do before building a footing?
Before starting with the construction of your surface foundation with footings, it is very important that you take into account the previous tasks that must be carried out for the construction of these, then we will tell you what these tasks are so that you can perform them in your projects that use this type of foundation.
Perform a geotechnical study or soil study
One of the first steps for the construction of the footings is to carry out the geotechnical study or also known as a soil study, for this reason it is very important that you consider the following aspects of this process.
- The stratigraphic cut and the level of the water table
- Know the degree of aggressiveness that the soil has
- Know all the mechanical characteristics of the terrain
- Be clear about the estimate of the depth that the foundation you are going to build should have.
Prepare the surface
It is of great importance, once you have made the clearing or emptying, that you prepare the surface of your terrain with a flatness sufficient enough to make it possible to carry out the layout of the footings.
Analyze and know the land where you are going to build
The analysis and previous knowledge of the terrain, where you plan to build a direct foundation by footings, is very important so that you can identify possible caverns or soft areas, these are causing different types of problems when executing a project, keep in mind Knowing about this or any other type of problem in advance is always going to be a great advantage to avoid wasting time or increasing the cost of the project, other aspects that you should keep in mind are the following.
Identify the presence of water on the ground
Another important aspect, prior to the construction of a foundation with footings, is the identification of the presence of water or groundwater level of the land, identifying this aspect will allow you to carry out the necessary drainage.
Look around you for factors that could harm the task
It is also of great importance that you consider and examine the existence of other foundations that are nearby and those services that are affected, these factors can surely alter the execution of the task.
Be careful with the concrete you are going to use
Before using concrete to make the footings, it is of great importance that you analyze and approve the plant that will manufacture it, the proposed work formulas along with the materials and components that the concrete will have ; Take care of verifying the result of breakage against compression, the equipment that is responsible for transporting it, the vibrating and the placement that will be used in the work.
Be very careful with shoring and falsework
Another important aspect is the verification of the technical documentation and the dimensions that will resist the weight of the concrete, the weight of the formwork, its own weight and the accidental overloads that may occur on them. Keep in mind that the falsework must be responsible for supporting a horizontal action of 2% percent of the order of the vertical load that is acting on them.
In the case of formwork
Check that both the elements that make up the formwork and their respective joints have the necessary strength to avoid possible deformations , an important aspect is to verify at all times the pressures that the concrete has and the effects that may occur with the compaction method .
Stake out the footings
In order to obtain data with great precision, stake out is carried out, this procedure is in charge of a surveyor who must have the help of a total station.
How is the layout of the footings carried out?
Staking out is a task that is carried out by placing stretchers or stakes that are made of wood in the corners of the excavation, this is responsible for indicating which is the level that will have to be lowered from the head of the stake, for In general, the marking of the dimensions of the footing is done with paint or plaster.
How to make a concrete footing?
The construction process of the footings fulfills several steps, among which are the excavation and cleaning concrete, the realization of the reinforcements, the provision of the joints and the curing of the concrete. Each of the steps to make a shoe we will tell you in more detail below.
After the staking of the footings is carried out, the ground must be excavated, this work is usually carried out with a backhoe with a spoon, this for the case where the ground is transit, for the case where the ground it is characterized by being conglomerate or rocky, it is best to use a hammer for this operation. The collected material can be reserved for later use as filling or in other cases transported to different landfills. Taking into account the depth that the excavation must have and the type of terrain that the project has, the slopes that are needed are used in order to provide stability.
Once the bottom of the excavation is reached, it must be leveled and checked, taking into account the conditions of admissible stress in the project, if the land is planned to make this type of foundation. It is very important that the measurements that the footings will have follow the project plans to the letter, with a tolerance of (+ or – 5 centimeters).
Use of cleaning concrete
Before the cleaning concrete is poured, it is important to clean the bottom of the excavation by removing any type of material in order to obtain a horizontal platform. It is important that the cleaning concrete elevation is properly marked and that it coincides with the lower elevation of the footing. If necessary, the lateral formwork must be placed immediately to check the dimensions and slopes; After carrying out this process, the cleaning concrete must be placed in order to level the bottom of the excavation and so that everything is ready to place the reinforcement.
Once the placement of the rebar is verified, the concrete elevation is set out using steel bars or painting on the sides. Strings are then placed between the marks to level the surface of the concrete.
Before performing the concreting process, it is important to clean the seating surface of any dirt or loose materials. The surface must be washed and in the event that puddles remain, the remains of water must be removed to make it dry and clean.
The concreting process is carried out with a crane or cupola pump, the concrete is poured directly at a height equal to or less than 1.5 meters, taking great care not to segregate and considering all climatic factors, all this taking into account the EHE standard.
When concreting, care must be taken so that the displacement of the reinforcement or formwork does not occur and you must try not to form cavities, joints or weak planes inside these sections. The concrete must be placed continuously or in layers, having short pauses so that when placing the next layer, the previous one is in a plastic state, the formation of the cold joint is avoided.
Needle vibrators should be used to compact the concrete, considering that the needle is inserted very deep into the vertical mass and must be withdrawn slowly and with a constant speed. It is also important that it be compacted in layers that are not greater than 60 cm. When compacting by layers, the vibrator needle should be inserted in the lower layer between 10 and 15 cm.
It is important that your project includes all the concreting joints. In the event that an unforeseen meeting occurs, it will have to be carried out in a normal way following the direction of maximum efforts; In the event that this cannot be done, you must form the greatest angle you can with it.
What happens if concreting is interrupted?
When concreting is interrupted, after 4 or 6 hours, the joint must be cleaned with a jet of air and water pressure or using any other type of system that correctly cleans the surface grout, loose aggregates, among others. In order that the aggregate is seen.
Concrete curing process
The concrete curing process is carried out by means of water irrigation or using a special curing liquid also known as film-forming agent, this process must be carried out for 7 days continuously.
This task must be carried out on the entire surface that is exposed after the leveling and vibrating of the final surface is carried out, with the aim that no plastic shrinkage cracks appear due to the loss of moisture. If you use a film-forming film, you must be very careful that it spreads over the entire wetted and saturated surface, but prevents puddles from forming.
If you decide to cure with water, this process will have a minimum duration of 4 days; In the event that the temperature is very low, the process will last up to 7 days. In the event that there is a lot of heat or humidity in the environment or that the wind is stronger than normal, the concrete curing process must be intensified.
The footings are divided into different types depending on the function required, the different types of footings that can be used in the projects are those that we will list below.
- Insulated shoe
- Combined shoe
- The running shoe
- Rigid shoe
- The solid shoe
- Flexible shoe
This type of footing is used to create singular columns, they are generally incorporated in structures that have a moderate load, they are applied in buildings or projects that have expansion joints and that fall into a single column in order to transmit the loads on the ground. There are different types of isolated footings, including flexible footing, deformable or rigid footing, eccentric footing or dividing footing, centered footing, rectangular footing, circular footing and square footing.
The height (edge) of this type of footing is less than its length (flight), this can be evidenced in both directions that the footing has. This shoe is responsible for supporting the compression and traction forces of the structure.
Rigid or deformable shoes
In this type of shoe, it can be seen that its edge is equal to or less than its maximum flight, measuring it in both directions of the shoe.
To this is added that the shoes that the shoes are categorized taking into account their measurements. In the case of rigid footings they have a reinforcement that allows them to withstand a greater bending force, their reinforcement has a diameter of 12 mm which prevents the effects of corrosion, the rigid footings must have a concrete coating of 8 centimeters and between 50 to 25 kg / m3 of iron.
Parting or eccentric footings
These footings are characterized by the fact that the load is not centered on the foundation, it is a case where the wall or the load-bearing pillar (dividing wall) that rests on a footing, continuous or isolated, is touching the limit of the property, and therefore the load cannot be centered on the foundation, this can happen for reasons of property ownership.
This type of footing is characterized by being braced or tied using a concrete or concrete brace that is reinforced with a section below the footing.
Rectangular shoes are characterized by having uneven sides.
In this type of shoe it can be seen that it has all the same sides.
These shoes are characterized by having all their sides equal.
Adjoining or combined footings are generally used as the foundation for two or more columns that are close together. Its main objective is to avoid eccentric loads in the final footing, in the combined footings the columns are not located in their center, but are located eccentrically, this happens very frequently in the perimeter columns.
Running or continuous shoes
This type of footing is responsible for supporting load-bearing walls that are closely aligned on a high, medium or low resistance ground. They are often used in rows of walls and columns to support aligned columns or load-bearing walls when they are close together.
The solid footings are used in continuous foundations, these are responsible for transferring the forces in a pyramidal manner, which has a triangular shape, the bearing wall that it has can be centered or eccentric. Their effort is compression and they may or may not have armor inside.
This type of shoe is characterized by the fact that it can withstand compression and traction forces, the angle it has does not amount to 45 degrees in the stress distribution triangle, to make its frame between 50 and 100 kg / m3 is required of iron.
This is all you need to know about the types of footings that exist and that are used in different projects, you also already know the previous procedures that you must carry out so that you do not have problems when making your footing, so do not stop aside these tips.