Designing a Foundation

 

Foundation

Foundation is the part of structure below plinth level up to the soil. It is in direct contact of soil and transmits load of super structure to soil. Generally it is below the ground level. If some part of foundation is above ground level, it is also covered with earth filling. This portion of structure is not in contact of air, light etc, or to say that it is the hidden part of the structure.

Depth of Foundation

Depth of foundation depends on following factors.
1. Availability of adequate bearing capacity
2. Depth of shrinkage and swelling in case of clayey soils, due to seasonal changes which may cause appreciable movements.
3. Depth of frost penetration in case of fine sand and silt.
4. Possibility of  excavation close by
5. Depth of ground water table
6. Practical minimum depth of foundation should not be less than 50 cm. to allow removal of top soil and variations in ground level.
7. Hence the best recommended depth of foundation is from 1.00 meter to 1.5 meter from original ground level.  

Footing

Footing is a structure constructed in brick work, masonry or concrete under the base of a wall or column for distributing the load over a large area.

Width of Foundation/Footings

The width of footings should be laid according to structural design. For light loaded buildings such as houses, flats, school buildings etc having not more than two storeys, the width of foundation is given below.
1. The width of footing should not be less than 75 cm for one brick thick wall.
2. The width of footing should not be less than 1 meter for one and half brick wall.

Different Processes in Foundation Work

The processes executed in the foundation works are given below. 
1. Excavation of earth work in trenches for foundation.
2. Laying out cement concrete.
3. Laying the footing in case of raft or column construction.
4. Laying Anti termite treatment.
5. Laying Brick work up to plinth level.
6. Laying Damp proof course on the walls.
7. Refilling of earth around the walls
8.  Refilling of earth in the building portion up to the required height according to plinth level.

 

Foundation of building

 

Foundation work for construction

 

Foundation of building-brick work

 

Foundation of building-filling of foundation



Precautions while designing 'Foundation'

  1.  A foundation should be designed to transmit combined dead load, imposed load and wind load to the ground. 
  2. Net loading intensity of pressure coming on the soil should not exceed the safe bearing capacity.
  3.  Foundation should be designed in such a way that settlement to the ground is limited and uniform under whole of the building to avoid damage to the structure. 
  4.  Whole design of the foundation, super structure and characteristics of the ground should be studied to obtain economy in construction work.

Ratio of Cement Concrete and Mortar for Foundation

  1.  The cement concrete 1:8:16 is generally used in the foundation of walls in construction work. 
  2.  In case of column raft cement concrete 1:4:8 is the best recommended ratio for it in the foundation.  
  3.  For brick masonry cement mortar 1:4 to 1:6 is used as loading condition.  

 In case of column and raft footings up to plinth level cement concrete 1:2:4 or 1:1.5:3 are used. 
Soil having Safe Bearing Capacity

Dry coarse and well graded dense sand have maximum shear resistance and maximum bearing capacity. In general submerged soil and clay have less bearing capacity.  

Precautions during Excavation of Foundation Work

The depth and width of foundation should be according to structural design.

  1.  The depth of the foundation should not be less than 1 meter in case the design is not available. 
  2.  The length, width and depth of excavation should be checked with the help of center line and level marked on the burjis.
  3.  The excavated material/ earth should be dumped at a distance of 1 meter from the edges. 
  4.  Work should be done on dry soil.  
  5.  Arrangement of water pump should be made for pumping out rain water.
  6.  The bottom layer of the foundation should be compacted.  
  7.  There should be no soft places in foundation due to roots etc.  
  8. Any soft/ defective spots should be dug out and be filled with concrete/ hard material

BR>

Foundation of building-roots in soil

Foundation of building- remove roots from soil

Foundation of building-fill pit with hard soil

Foundation of building-soft soil

Foundation of building- remove soft soil

Foundation of building-fill soft soil pit


 
117  Comment(s)
123Next  >>
Narendra
By Narendra -  On  3/30/2014 4:19:22 PM
Is size stone masonary must bellow plinth beam?
 
Anonymous
By Anonymous - On 3/22/2014 10:22:09 AM
Please help me with giving me the information to construct a 4 stories new building. I don't know what would be the foundation design. The building is G+3
 
Anonymous
By Anonymous - On 3/13/2014 8:40:52 PM
good
 
Vijay K Vairagade
By Vijay K Vairagade -  On  3/8/2014 9:37:50 PM
Very Informative and useful to the builders and contractors and specifically for me as a Individual Home Builder. THANKS a LOT.
 
Anonymous
By Anonymous - On 2/26/2014 5:26:36 PM
Hi, I have a question. Should the plinth beam be below the ground level or above?
For a 3 storeyed building, how much depth should be given in foundation excavation with red soil type?
 
Anonymous
By Anonymous - On 1/8/2014 3:41:37 PM
design like bildg. foundation for making minimum 02 storey bldg.ang roof slab design details etc. also to be display. k.ezhil vanan,civil engineer.
 
Anonymous
By Anonymous - On 12/30/2013 2:06:43 PM
very nice and very useful to civil supervisors
 
Anonymous
By Anonymous - On 12/13/2013 2:00:55 PM
VERY NICE & VERY USEFUL TO ALL CONSTRUCTION PEOPLE
 
Anonymous
By Anonymous - On 11/28/2013 12:17:05 PM
A nice 1, but to level for the lay of concrete before the bricks
 
Anonymous
By Anonymous - On 10/18/2013 12:49:46 PM
Nice ! it is so helpful to me . the figures and explanations make me more understand
 
Anonymous
By Anonymous - On 8/2/2013 11:59:00 AM
very nice to understand .can u give us more information on foundation by figures
 
Anonymous
By Anonymous - On 7/6/2013 4:32:28 PM
simply superb..can u pls tel me how to find t xact dimension of a footing for various heights of a building?..
 
Anonymous
By Anonymous - On 7/6/2013 4:28:23 PM
simply superb..can u pls tel me how to find t xact dimension of a footing for various heights of a building?..
 
Anonymous
By Anonymous - On 6/26/2013 8:46:55 PM
much needed information
 
Anonymous
By Anonymous - On 6/18/2013 10:58:12 AM
the article is very helpful...and is greatly explained about each and every corner of the work....thnx...
pls tell me the length and width of the foundation for a four floor buliding...like hospitals extra...in uttar pradesh side type of soil...
 
Anonymous
By Anonymous - On 6/12/2013 9:45:19 PM
its amezing for me its is ful of knowlege
 
Parvez
By Parvez -  On  5/26/2013 1:37:22 PM
i want to construct a new building with ground plus 4 floor , what will be the construction cost of whole building measuring G+4 - 3800 sq/feet
 
Anonymous
By Anonymous - On 4/22/2013 10:09:26 PM
I feel that Mr. S L Gupta (Civil Engg)is right and in case the level of the floor is to be raised than additional beam i.e. strap beam shall be used.
 
Anonymous
By Anonymous - On 4/5/2013 5:12:19 PM
Very interesting and helpful information provided.

KEEP IT UP
 
cosntruction novice
By cosntruction novice -  On  4/1/2013 4:11:25 PM
For foundation and columns, I have been advised to use "dust" rather than "ghagger sand" -- which my contractor is using. ANy thoughts? How do I differentiate dust from what is being used right now..
 
sam (Civil Engg)
By sam (Civil Engg) -  On  4/1/2013 4:11:25 PM
Hi 
I am designer, i am offering if any one want to design their home (Structural design, architectural design, vaastu, , plans, 3d views) call me +919810636565
 
trsvijith
By trsvijith -  On  4/1/2013 3:41:15 PM
this part is very critical stage of a dream home, so the article is vey helpful
 
S L Gupta (Civil Engg)
By S L Gupta (Civil Engg) -  On  4/1/2013 11:33:29 AM

Dear Murthy


          Lay or construct plinth beam at plinth level i.e. at floor level.

 
GVS Murthy
By GVS Murthy -  On  4/1/2013 10:46:47 AM

I would like to construct my new house one and half feet above the road level. Should the plinth beam be at ground level and raise a brick wall up to required level then go for filling or raise the level of the ground by filling up to required level then go for plinth beam, which one you suggest for the good strength of my house with four levels. Thanks & Regards

 
Anonymous
By Anonymous - On 2/14/2013 10:44:20 AM
Sir,

Can i get full design of single storeyed house(structurel)
 
Anonymous
By Anonymous - On 2/7/2013 8:35:30 PM
The information given is very important for civil engineer.realy good details
 
Anonymous
By Anonymous - On 1/5/2013 8:51:36 PM
SIR
Can u guide me How to design corner rcc foundation for long span 6m and show me the diagram
CHRISTOPHER
 
Anonymous
By Anonymous - On 1/2/2013 1:48:16 PM
it include the best and good information. it is very helpfull .
 
samarendra nath das
By samarendra nath das -  On  12/1/2012 12:42:26 PM
I have a plot north facing 60mt distance from railwaytrac.the plot is about 6ft down from road level.I have made a self design of house plan of G(Parking)+3floor of 1000sqft area for each floor.But do not know how to make the design of foundation ,pillar, beam etc.Please help me for giving the design and advice.Than Q
 
Prabhat Kumar
By Prabhat Kumar -  On  11/3/2012 1:40:18 PM
plzzz explain the exact mean of plinth & plinth level...??? n give with a suitable diagram.. plzz..???
 
Anonymous
By Anonymous - On 10/8/2012 10:36:16 PM
Thank you.I find your article very helpful.
However, concrete mix of 1:8:16
in foundation as depicted in the figure above is too weak.I would suggest 1:2:4.

Thank you
 
Anonymous
By Anonymous - On 9/29/2012 2:12:55 PM
This informaation is very helpfull . But i have one quetion "what points should kept in mind while designing foundation on black cotton soil"
 
Dipankar Gharami
By Dipankar Gharami -  On  8/17/2012 12:23:50 PM
I like it and i am interest about foundation
 
DEBASISH SARKAR
By DEBASISH SARKAR -  On  7/21/2012 5:43:32 PM
hi every body,this is debasish here.i am going to construct my o3 story house.i want to make all wall load bearing 230mm thick.The site is at nadia,West Bengal(delta of Ganga).
please guide me for foundation.what should be the depth,what should be width of first layer of brick?i want to use fly ash bricks.
 
lovysta
By lovysta -  On  6/13/2012 11:32:10 AM
hello! in short i lack words to say, becuz everything i xpected, i found it here. please keep up, you're doing perfect. Good day
 
rajneesh
By rajneesh -  On  5/27/2012 7:27:57 PM
construct in nagpur
 
Anonymous
By Anonymous - On 5/5/2012 6:48:44 PM
Wow! It is very very interesting and helpful to me. I am B-tech (Hons) in Architecture from Nigeria. Thanks
 
Anonymous
By Anonymous - On 4/30/2012 4:43:58 PM
Gharexpert is very use full for civil professional

Thanks for this
 
Anonymous
By Anonymous - On 4/16/2012 3:48:05 PM
Is ther any criteria of depth below existing ground in order to decide for anti termite treatment? Does it have any co-relation with roots of plants?
 
Anonymous
By Anonymous - On 3/18/2012 9:07:45 PM
Lovly,By engr Saliu Asuku yahaya
 
 
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