**3.4 Assembly of a prefabricated house with elements of reinforced concrete**

The assembly process, perform the following process (**Figure 8**).

*Low-Cost Single-Family House through The Use of Precast Reinforced Concrete Elements DOI: http://dx.doi.org/10.5772/intechopen.98430*

**Figure 7.**

*(a) Isometric view of VUF 01. (b) Isometric view of VUF 02. (c) VUF 03 isometric view. (d) VUF 04 isometric view. (e) VUF 05 isometric view. (f) VUF 06 isometric view.*

#### **3.5 Structure of prefabricated elements of reinforced concrete**

The structural system of precast concrete elements comprises foundation beams, floor slabs, walls and ceiling, under an approach of articulated structural panels with anchors that support stress requests. The elements must reach a sufficient resistance for their handling and transport to the assembly place. They must withstand the weather and inclement places.

Each element is made of reinforced concrete of 210 Kg/cm<sup>2</sup> with mesh every 0.20 m in both directions of iron with a diameter of 3/8 in diameter and in the perimeter near the edge there is an iron with diameters of 1/2″ in diameter, reinforcements are also applied in corners and critical places. Lifting and transport devices are installed. It is possible to use various anchoring systems, as long as it responds to the stress requests required by the prefabricated parts.

Two pieces are shown with exposed structures, the others show a similar constitution (**Figure 9**).

#### **3.6 Production time and assembly of a prefabricated house**

For this analysis, we worked with the value of the unit time, which is the direct relationship between the metering and the unit yield of the item, in relation to the

#### **Figure 8.**

*(a) Foundation installation. (b) Foundation slab. (c) Front wall installation. (d) Installation of sidewalls. (e) Installation perimeter wall. (f) Installation of interior walls. (g) Ceiling installation. (h) Completion of work finishes.*

value of the direct cost. The individual values per item and the total per dwelling, were obtained according to the S10 program, which gives us a gross unit time of the need in days and that is required for the execution of the work.

*Low-Cost Single-Family House through The Use of Precast Reinforced Concrete Elements DOI: http://dx.doi.org/10.5772/intechopen.98430*

The value obtained is an indicative and orientate parameter that allows us to adjust the necessary times, according to an adjusted time analysis of unit times and the Gantt chart is made. The minimum and effective duration of production and assembly of the prefabricated houses has been determined, which are shown in the following (**Table 7**).

The unit time of VUF Prefabricated Single Family Housing has been determined from 32.07 days in VUF-01 to 65.70 days in VUF 06. Adjusted time with a Gantt diagram of VUF Prefabricated Single Family Housing has been determined from 4.00 days in VUF-01 to 6.00 days in VUF 06 (**Figure 10**).

El Unitary time of VUF houses is adapted to a quadratic polynomial trend of y x 0.005x<sup>2</sup> + 0.6022x + 12,706 (R2 x 0.9916, 95%). El Adjusted Unit Time in Gantt of

**Figure 9.** *(a) Structure of a side piece with window of the VUF 01. (b) Structure of a front part of the VUF 01.*

VUF houses is adapted to a quadratic polynomial trend of y – 0.0003x<sup>2</sup> + 0.0876x + 2,004, (R2 x0.9072, 95%).

The unit time on constructed housing area expressed in days/m<sup>2</sup> , has been determined, the lowest value in VUF-04 of 1.09 and the highest value found in VUF-01 of 1.24. Performing calculations at set times in the Gannt chart has achieved the lowest value in VUF-06 of 0.10 and the highest value in VUF-01 of 0.15.

These indices are achieved without increasing the efficiency of the machines and equipment, by carrying out a greater analysis with efficiency indices, the production level would increase and achieve cost reduction, which implies producing larger units of prefabricated elements per unit of time. There is a direct relationship between execution times and investment requirements, it is shown in the following (**Table 8**).

It presents a direct relationship between the execution days and the investment requirement, expressing that, the greater the number of execution days, the greater the investment. The largest investment is concentrated in the production of prefabricated parts.


#### **Table 7.**

*Unit time (TU) and adjusted (TA) in VUF Gantt.*

**Figure 10.** *Unit time and adjusted execution of the VUF.*

*Low-Cost Single-Family House through The Use of Precast Reinforced Concrete Elements DOI: http://dx.doi.org/10.5772/intechopen.98430*

The investment trend responds to a cubic polynomial function where the cusp is on the second day of execution, there is a decrease on the fourth day. However, it must be understood that the work can be executed within four to six days, therefore, before starting the execution of works all available investment must be available (**Table 9**).

Of the trends of the polynomial functions, there are three subtypes in the relationship of execution time and investment requirement, which is expressed in three values close to 1 of the coefficients of determination. Which tells us that according to the sub types of prefabricated houses, the cost of the work and the investment requirements can be adjusted (**Figure 11**).

#### **3.7 Costs and budgets of VUF prefabricated single-family houses**

#### *3.7.1 Direct costs VUF*

The direct cost are all those expenses that are directly related to the construction of a work, specifically it will be expressed in the amount of labor, materials and equipment involved in the execution of a work, which will be expressed in national currency and in US dollars at the change of budgeting.

Six types of houses have been designed for a production system of prefabricated elements of single-family houses in order to optimize resources and adapt to a minimum production line at scale, be it on a production line in plant or at the foot of the play.

Architectural and structural plans have been developed for each type of house designed, from which the corresponding measurements have been made. These


#### **Table 8.**

*VUF daily investment requirement.*


#### **Table 9.**

*Inversion polynomial functions VUF.*

**Figure 11.**

*Polynomial lines trend reversal time in execution VUF.*

measurements were processed in the cost and budget program S10. A summary of direct costs is presented in the **Table 10** below.


#### **Table 10.**

*Direct cost of a VUF in US suns and dollars.*

The costs of the manufactured houses shown in the table are in Peruvian currency in soles, in US dollars and the cost per square meter, according to the type of VUF house. For each item, a unit cost analysis has been carried out indicating the amount of materials used and considers the equipment and machines necessary for its manufacture and assembly (**Figure 12**).

The direct costs in dollars of basic housing range from US \$ 7,786.61 to US \$ 16,350.91 and are accessible to the economies of populations in need of housing. These prices are competitive with the costs offered in the real estate industry.

The bond that the Peruvian government assigns to the victims of collapsed or uninhabitable houses due to disasters according to RM No. 012 2018 Housing [9] establishes a housing reconstruction bond for Ichupampa, Lari, Tuti and others in Arequipa, of S/43,497 y its value in US dollars is \$ 13,171.

*Low-Cost Single-Family House through The Use of Precast Reinforced Concrete Elements DOI: http://dx.doi.org/10.5772/intechopen.98430*

**Figure 12.**

*Direct cost of VUF and its relationship to emergency bonds.*

The value of the house VUF 01, VUF 02, VUF 03 and VUF 04 are below the bonus assigned by the Peruvian Government. The proposal to serve in situations of need for housing and post-emergency is framed for direct care, effectively and in a short period of time. The correlation analysis between the surface of the VUF and the cost in dollars of its building has a linear trend and the coefficient of determination is very high.

The direct cost per square meter of manufactured housing, in US dollars, ranges from \$ 273.23 to \$ 301.46, these amounts are one of the lowest compared to traditional construction costs.

According to Ministerial Resolution No. 086–2020-Housing [10] it provides a family housing bonus for families in need of S/. 37,625 soles, in US dollars it is equivalent to US \$ 10,722.43 and VUF 01 and VUF 02 houses are below this value.

#### *3.7.2 Total costs. VUF*

The total cost of a work is defined as the sum of direct cost-plus indirect costs. For our case, indirect expenses are covered by overheads of 10% of direct cost plus 10% profit; from which a subtotal is obtained and from this value is added 18% corresponding to the IGV, resulting in the total cost. For a production line it is common for indirect cost to be a fixed and non-alterable proportional value in costing processes.

The value of the total cost has been obtained in soles and then it has been converted to US dollars according to the exchange rate and the cost per square meter is established in US dollars (**Table 11**).

The total costs in dollars of basic housing range from US \$ 11,025.83 to US \$ 23,152.89 and are accessible values for the economies of populations in need of housing (**Figure 13**).

The bond that the Peruvian government assigns to the victims of collapsed or uninhabitable houses due to emergencies or disasters according to RM No. 012 2018 Housing The housing reconstruction bond of US \$ 13,171 would only allow VUF 01 and VUF 02 to be reached.


#### **Table 11.**

*Total cost of prefabricated single-family housing (VUF).*

**Figure 13.** *Total cost of VUF and its relationship to emergency bonds.*

The bonus that the Peruvian government assigns for its own roof according to Ministerial Resolution No. 086–2020-Housing of \$ 10,722.43 US dollars would only be enough for VUF 01.

It is necessary to highlight that the bonds assigned to the population in need with the amounts assigned are incorporating 100% of the amount in the construction of a house, and under these conditions the recipient population can have a house without any particular investment contribution from the beneficiary. At present, it is usual for the beneficiary who receives these bonds to make a larger contribution to the received bonus, in some cases it can exceed up to five times the amount, and in many cases the desired house is not completed.

The correlation analysis of the total cost and the construction area of the VUF has a parallel, increasing linear trend and the coefficient of determination is very high and is the same value as that obtained in the direct cost.

*Low-Cost Single-Family House through The Use of Precast Reinforced Concrete Elements DOI: http://dx.doi.org/10.5772/intechopen.98430*

The trend line of the direct cost, the coefficient of determination, is y = 257.70x + 860.99 R2 = 0.9906. The trend line of the Total cost and the coefficient of determination is y = 364.91x + 1219.2 R<sup>2</sup> = 0.9906.

It is usual to calculate the cost trend in a production line from the direct cost, and on this amount an additional percentage is assigned to the value of the production line, which does not alter the cost trend. In our case, the value added to the specific direct cost is proportional and unalterable during the production and building processes, which is reflected in the trend lines and in the determination coefficient.

The direct cost per square meter of prefabricated housing, in US dollars ranges from \$ 386.85 to \$ 426.86, these amounts are low in comparison and are competitive costs with the real estate industry that exists in the city of Arequipa – Peru.
