Some useful guidelines to develop a building foundation

While building up a foundation for a building, adequate knowledge is required with some particular steps to make sure that the footings will retain the weight of the building through rest of time.

The purpose of building foundations is to bear the load of the structure as well as disperse the load to the soil in greater cross sectional area. The foundation should have the capacity to resist the load of the structure along with the live loads and environmental factors.

A safety factor is arranged for safety all through the foundation design. The foundation is built up on the basis of the design. Given below, some vital steps, which should be abided by, at the time of constructing & designing building foundation.

1: Survey and Stake Out Footprint - A professional surveyor should execute this step. The surveyor will settle on the exact distances from the property lines. It makes sure that the building will set out perfectly and abide by the code. The corners of the building will be marked with surveyor’s stakes.

Then the surveyor will arrange offset stakes about two feet out from the surveyor’s stakes. The digging for the foundation will start by applying the offset stakes as the guides. It accomodates extra room so the work can be performed on the exterior foundation walls.

2: Excavation - A structural engineer is required to define the depth of the excavation. All surface soils should be eliminated to uncover the soil that is properly compressed to carry the weight of the building.

The depth will differ for each building. The top of the footing should remain underneath the frost line since it resists the concrete from cracking when the freeze-thaw cycle happens in the soil that encircles the building.

3: Footings - A footing stands for a poured concrete pathway that is applied to expand the weight of the building from the foundation walls to the soil. They are larger as compared to the foundation walls that they are supporting and create the perimeter of the building. In some cases, there exist extra footings which are provided inside the perimeter to provide support to the load-bearing walls.

4: Sub Slab - Normally, plumbing lines are arranged from the street to the building’s basement by passing over or even below the footing. It occurs for the buildings which contain their own separate sewage facility or drain field. A poured concrete slab is used to cover these lines.

5: Foundation Drainage System - Subsurface water is preserved and pushed away from the foundation to get rid of pooling water or flooding. The foundation drainage tile is constructed with an incessant run of punched drainage pipes which are implanted in gravel along the foundation of the building. In some areas, a sump pump may also be needed to facilitate accumulating the subsurface water.

To gather knowledge on other steps, go through the following link civilengineersforum.com



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Published By
Rajib Dey
www.constructioncost.co
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How to start marking for foundation

This construction video provides detailed guidelines on foundation marking. In the video, the plan of building is given for living room and kitchen room. The center line marking is also provided with 6 numbers of columns. Initially, you have to set the base point as it is very crucial for marking. After that, a base line is arranged from that base point with a thread for fixing the second point.

The centre line of the wall perpendicular to the long wall, is marked by making a proper angle. Right angle is arranged by creating triangles with sides 3,4 and 5units long. If we set the two sides of the right angles triangle to be 3 m, and 4 m, then the third side i.e. the hypotenuse is assumed at 5 m. A steel tape should be used to fix all the dimensions.

The formula is used here as √(L2+B2).

The right angle can be fixed by applying a theodolite. This instrument is very useful in fixing acute or obtuse angles. Small right-angled Projections are generally laid out with mason’s square.

Proper marking of the foundations is specifically important for new walls to make sure that the foundations contain the exact size and are in the perfect position to bear the load of the wall. Good foundations are essential to make sure that no movement can occur because any movement can lead to cracks and problems in the building that is supported with the foundation.

To get the complete instructions, watch the following video.

Read more

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Published By
Rajib Dey
www.constructioncost.co
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How to make the design of a Foundation

Foundation is the portion of structure underneath plinth level up to the soil. It is directly connected with soil and it transfers the load of super structure to soil. Normally, it is located under the ground level.

If some portion of foundation is situated over ground level, it is also enveloped with earth filling. This part of structure is not in touch with air, light etc, It is considered as the concealed part of the structure.

Depth of Foundation: Depth of foundation is based on the following points-

1. Sufficient bearing capacity should exist
2. Depth of shrinkage and swelling for of clay soils, because of change in climate that may lead to appreciable movements.
3. Depth of frost penetration for fine sand and silt.
4. Chances of availability of excavation
5. Depth of ground water table
6. Practical lowest depth of foundation should not be under 50 cm. to facilitate subtraction of top soil and deviations in ground level.
7. So, the desired depth of foundation should vary from 1.00 meter to 1.5 meter from original ground level.

Footing: Footing belongs to a structure that is built up in brick work, masonry or concrete under the base of a wall or column for dispersing the load over a extended area.

Width of Foundation/Footings

The width of footings is based on the structural design. For light loaded buildings like houses, flats, school buildings etc which do not contain over two stories, the width of foundation is provided below :-

1. The width of footing should not be under 75 cm for one brick thick wall.
2. The width of footing should not be under 1 meter for one and half brick wall.

Various methods in Foundation Work: The following methods are involved in the foundation works -

1. Excavation of earth work in trenches for foundation.
2. Work out cement concrete.
3. Set the footing for raft or column construction.
4. Arrange Anti termite treatment.

5. Set Brick work up to plinth level.
6. Set Damp proof course on the walls.
7. Refilling of earth around the walls
8. Refilling of earth in the building portion up to the desired height as per plinth level.

For more: http://constructioncost.co/how-to-make-the-design-of-a-foundation.html

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Published By

Rajib Dey

www.constructioncost.co

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How to resolve issues prior to foundation design

To make a perfect foundation design, the following vital points should be taken into consideration:-

Make sure that the foundations are maintained as extremely shallow, suitable with atmospheric impacts and strength of the surface soil; specifically in flooded ground. Excavation in fatally flooded ground seems to be costly and slow.

Get rid of costly and complicated shuttering details specifically in hardened rafts. Proper care must be taken to examine the build aptitude.

The economics of the design can be significantly impacted with various factors like drop in the piling costs, upgrading in ground treatment, progression in soil mechanics, etc and various standard solutions are now obsolete. So, it is necessary to evaluate construction costs and methods on a regular basis.

Designers should be well versed with the presumptions provided in design, the inconsistency of ground conditions, infrequent inapplicability of refined soil analyses and the utility of construction.

Make proper evaluation to check the consistency of the soil.

Impact of construction on ground properties, i.e. vibration from piling, degradation of ground disclosed with excavation in unfavorable weather conditions, deduction of overburden, seasonal difference in the water-table, compaction of the ground through construction plant.

Impact of deviating shape, length and inflexibility of the foundation, and the requirement for movement and settlement joints.

Consequences on finished foundations with sulfate attack on concrete, ground movements because of frost heave, reducible clays, and the impacts of trees; also alterations in local environment, e.g. new construction, re-routing of heavy traffic, foundation of plant in adjacent factories inducing impact and vibration.

Rapid but costly construction may be more cost-effective as compared to low-cost but slow construction to clients requiring quick return on capital investment.

Impact of new foundation loading on existing nearby structures.

To get more information, go through the following construction video Civilblog.Org

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Published By

Rajib Dey

www.constructioncost.co

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Variation among pad foundation, strip foundation and raft foundation

Shallow foundation is generally described as foundation that contains founding level below 3m from ground surface. Alternatively, when the breadth of the lower most part of the foundation is more than the depth of the lower most part of the foundation from the uppermost of the soil, i.e. Ground Level then it is defined as a Shallow Foundation. It transmits building loads to the earth adjacent to the surface. Shallow foundations comprise of spread footing foundations, mat-slab foundations, slab-on-grade foundations, pad foundations, rubble trench foundations and earthbag foundations.

Pad foundation stands for the foundation that is specifically developed for retaining concentrated loads out of a single point load like structural columns. Pad foundations are specifically designed to provide support to individual or multiple columns, scattering the load to the ground underneath. They are usually square or rectangular in plan, the plan area is defined by the allowable bearing pressure of the soil. The shape in plan will be determined by the arrangement of the columns and the load will be transmitted into the soil.

The thickness of the slab should be adequate to make sure that distribution of the load is perfect. The top of the pad should have been sloping (i.e. the pad is denser in the centre as compared to it is at the edge). It provides a cost-effective solution, though there are construction issues which are associated with casting the slope.

Strip foundation is utilized to provide support to a line of loads like load-bearing walls. As for example, closely-placed columns deliver the imperfect application of pad foundation and strip foundation may be a good choice.

Raft foundation comprises of a concrete slab which expands over the entire loaded area in order that loads from whole structure are expanded over a broader area that results in minimizing of the stress of foundation soils. Besides, raft foundation is useful for resisting differential settlement.

Ref.: www.engineeringcivil.com

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Published By

Rajib Dey

www.constructioncost.co

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