Advantages and Disadvantages of On-site and Off-site Construction

The needs and restrictions at your construction project may make you choose between one of the two main methods of construction: on-site and off-site. Both are widely used in today’s construction industry, depending upon the requirements at the site and according to design.

What is On-Site Construction?
On-site construction is the more traditional method. Here, structures are assembled from raw materials at the site itself, hence the name. The method has to be carried out sequentially and materials needs to be stored and used at the site.

What is Off-Site Construction?
With modern technologies, off-site method of construction has become possible. In this, parts or blocks of the structure are constructed in a designated factory or yard in standardized process. Then, these pre-built blocks are carried to the project site where they are assembled together to form the structure.

Both of the above methods have their own advantages and disadvantages, which make them suitable to different scenarios. Let’s discuss them below.

On-Site Construction

Advantages:

1. Customized Design: Since there is no restriction on what shape of objects are available of construction, there are limitless customization options in this manner. In fact most non-standard designs have to rely upon the on-site method just for this.
2. Alteration: After the construction you can easily modify the structure with this method. It doesn’t require you to depend upon third-party construction factories to add or change a room in your house that has been constructed in the traditional method.
3. Space-friendly: Transporting precast blocks in tight urban areas can get simply impossible. More often, it’s prohibitively expensive. In these scenarios you have no choice but to construct everything on-site.

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Published By

Rajib Dey

www.constructioncost.co

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Minimum Foundation Depth for Houses

The foundation of a house is what holds the structure up, carries its entire weight. When you try to design a new building, you must consider how deep the foundation should be in order to properly support the building. This is called the foundation depth. It is measured by the vertical distance between the footing and the natural ground surface.

Expansive Soil: One thing to be kept in mind here that light soil has expansive properties. Due to wet and dry weathers, the soil can inflate and condense accordingly. This changes the effective natural ground surface level.

As a rule of thumb, foundations are placed under this level of soil, where such changes do not occur. That is about a meter in depth, in most cases.

However, this can be significantly higher if you have expansive soil or black cotton soil on site. This type of soil can take a load of 200-300 kpa only. Any more and the building will settle.

Groundwater Under Soil: Also, another thing to be kept in mind when deciding the minimum foundation depth is the presence of water under the ground. If the groundwater table is close to the foundation, then the soil under the foundation can flow around.

Water seeps up into the soil and makes it weak. To resist this, the bottom of the footing should be placed at a deep enough place where groundwater does not seep into the soil any more.

Cold Regions: Frost changes the nature of soil. It heaves the soil upward and that may create cavities underground. For this reason, in cold regions where snowing and/or ground frosts are normal, the foundations for outside columns or walls should be placed below the level down to which frost can affect the soil.

In the northern US, this can be as deep as 1.5 meters. Further, if the internal walls are heated, then the outer walls would require a deeper foundation so that the heat does not alter the soil properties.

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Published By
Rajib Dey
www.constructioncost.co
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The four types of Shallow Foundation

Shallow foundation is applied in cases where we can find good load-bearing soil at a rather low depth. The foundation depth must meet the safety requirements of the breakdown. That is, after the application of load, the complete structure settlement will be within acceptable limits.

We can use the following four types of shallow foundations: Spread Footing, Combined Footing, Raft Foundation and Ring Foundation.

1. Spread Foundation: You need to spread the load from the column or wall to a larger area, you should use Spread Foundation. The width of the footing area is much wider than the wall or column.

The spread footing that is used to support a wall is called a wall footing or continuous footing. The top of the footing may be stepped or tapered, increasing the width gradually from wall or column to the base. They are of the following types:

a) Strip Footing: This primitive type of footing has been conventionally used in most constructions historically, before more modern inventions. They are mostly made of stones, masonry or concrete. The strip footing that is constructed of stone blocks generally has a stepped top. In modern days, however, the use of strip footing has become next to obsolete. Only in some light loading residential construction is strip footing still used.

b) Isolated Footing: When you provide footings under columns separately in a framed structure, it is called Isolated footing, pad footing or column footing.

In most cases, square footings are used under columns. However, space restrictions may force you to use rectangular footings. In case of circular columns, circular footings may be used, though it is not common. It may be used in special circumstances where construction work is difficult, or the load has to be dispersed very equally.

2. Combined Footing: When two columns are too close to make separate footings for each, then their footings are combined. These may be of the following three types:

a) Rectangular footing: These are the most common types of combined footing. It’s basically two square footings constructed together. This is used when each column is bearing the same load and of the same size.

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Published By
Rajib Dey
www.constructioncost.co
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Construct Earthquake Resistant Buildings by Simple Means

The engineering science is continuing to advance in response to seismic threats. There have been significant breakthroughs in the field. However, most of them are very complex and require exceptional machinery. Not to mention, expensive as well. However, there are some simple ways to build a structure that will be resistant to earthquake damages up to a certain level.

In areas where seismic activity is not too harsh, we can utilize these techniques to same money and complexity but make the building resistant to seismic activities.

Structure Stiffness: The most traditional way to fight quakes is to use stronger materials to construct the building. Stiffer or heavier members can be used to fight the lateral forces generated during seismic activities. For special quake-proof structures, ACI codes prescribe at least 10” thick members.

Geometrical Absorption: The building can be planned in such a regular and special geometrical shape that it disperses the seismic forces evenly so that no particular member experiences excessive force. This naturally fares much better than a poorly-planned unsymmetrical building.

For existing buildings that are structurally asymmetrical, you can use seismic joints and expansion points in places where the forces are dispersed unevenly. Providing extra columns, shear walls, and framing can make the weaker section withstand the extra forces to a good level. Parking levels should have extra reinforced columns in order to negate the soft story effect.

Lateral Force Resistance: Using three types of lateral force resisting systems, we can try to negate much of the seismic forces. These are:

1. Moment Resisting Frame System: it is designed to resist all types of earthquake generated forces acting on the structure. They can be customized to fit the seismic activity scale of the region.

2. Building Frame System: these are designed to resist gravitational loads only, but they function excellently in that. A shear wall is added to resist the lateral forces acting on structure.

3. Dual Frame System: this is a combination of the above two systems. Shear walls along with moment resisting frames work excellently to fight off the vibrations and displacements from an earthquake. But, of course, they are more complex and costlier to build.

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Published By
Rajib Dey
www.constructioncost.co
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How to Control Reinforcement Activities On-site

It is imperative to control reinforcement activities in a building construction site. Otherwise the building may get damaged due to any shift in loads, or may simply break down at the slightest seismic activity.

First of all, you need to hire one or more qualified engineers to oversee different parts of the construction process. Aslo, you need to assign as many assistants as necessary to them.

A. Planning Phase: You need to study the documents concerning the project carefully as to divine the exact requirements. You also have to make sure the planning goes according to technical specifications. Then locate the provisions regarding mode of measurement in item fee agreement.

Check the objects payable which includes reinforcement, and whether or not laps, spacers and chairs are payable or inclusive. Arrange the required applicable codes,requirements and different related documents at the website for reference and study.

Study the tender drawings without fail. Calculate quantity as in keeping with the preliminary drawings, Dia clever and grade sensible. Mastermind the necessary pertinent codes, standards and other related archives at site for reference and study.

Study the delicate drawings without fail.Calculate amount according to the starter drawings, Dia savvy and grade insightful. Set up the monthly shrewd obtainment plan according to the development plan. Get ready to obtain a calendar of authoritative alongside support plan.

Plan for spread squares and joins (whenever required) ahead of time to get the required quality of spread squares thrown at site. Get Dia shrewd and grade savvy amounts from creator for singular amount contract if drawings were not accessible at starting phases of undertaking for arranging acquisition.

Permit a stock of 45 days while arranging obtainment or relying on the accessibility. Indent just 90% of amounts of absolute necessity till you have every endorsed attracting to keep away from varieties because of configuration/drawing corrections.

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Published By
Rajib Dey
www.constructioncost.co
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Safety Plan for Concrete Formwork

Safety first! The age-old construction motto has never wavered even in modern days. Accordingly, it is in effect also when planning for formwork systems. A proper plan that observes safety protocols strictly will let you avoid undesirable circumstances arising in work. Also, it will reduce the chance of accidental happenings.

Work supervision, equipment utilization and construction procedures all must ensure the safety of the workers. Not only that, the plans need to be laid out in such a manner that the people using the building will not come under any foreseeable accident. Designers, planners, and engineers all must conform to well-established safety standards such as OSHA in order to ensure proper safety and security.

Let us see now the various facets of Concrete Formwork.

1. Supervision and Inspection: Proper supervision of work is of paramount importance while work is going on in order to ensure that all safety protocols are being obeyed. This comes active in times of formwork placement, concrete pouring, and formwork stripping.

Not only this, modifications in field on the falsework, erection procedure and forms should always be properly inspected first. Always, these should be done only after the principal designer has given the green signal to them. The load on the formwork needs to be sharply observed at all times lest it breaks down under excessive loads it was not designed to uphold.

2. Platforms and Access for Workers: For work required at elevated positions, worker-accessible platforms need to be raised. These platforms and the pathways to access them should be very carefully erected. Ladders need to have proper rest on solid structures at the top, or need to fastened in case they are very long.

Some of the particularly tricky structures such as bridges may require special scaffolding or safety nets in order to ensure proper access and prevention of accidents. These scaffolds, platforms, or other access means must conform with OSHA standards.

Unauthorized individuals, onlookers and loiters are not only a distraction to work, but they can actually bring or become trouble to everyone involved. To prevent this, barriers and safety signs need to be placed around the construction site from the very beginning of work.

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Published By
Rajib Dey
www.constructioncost.co
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About Precast Concrete Piles - the Pros and Cons

The most common type of them, a precast concrete pile is a deep foundation used to transfer loads from a upper, soft layer of soil to a hardar, capable lower layer. They can be rectangular, square, round or polygonal in shape. Extra reinforcements are provided in the concrete so as to provide support for the forces received before the instalent.

The precast concrete piles are constructed in a casting yard. Then they are transported to the required location and installed as necessary. They are constructed by pouring the concrete in a conventional reinforcement cage. This has several steel bars in horizontal and vertical positions, held together by individual or spiral ties.

Types of Precast Concrete Piles - There are two main categories into which we can divide:

1. Driven Precast Concrete Piles: It is precast in a construction yard and then hammered into the soft ground at the target location. At most they can go up to 40 feet deep.

2. Bored Precast Concrete Piles: After they are made in the construction yard, they are transferred to the target location. The location already has boreholes for the piles; they are just lowered into these holes. Any space remaining between the bore hole and the pile is grouted.

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Published By
Rajib Dey
www.constructioncost.co
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