opalu:
There is a vital aspect of using inadequate foundation. The determination of the type of foundation a building requires is done by the Structural designs matched with the Soil Investigation/tests. The Structural Engineer through his Analysis estimates the entire loads that is coming on the foundation at various points. Where the foundation required is raft, he determines the depth that will be both SAFE and COST EFFECTIVE. But in a conflict between safety and Cost, the safety takes precedence or else the architect is called in to redesign the building to make it smaller/lighter.
Last year, I did an entire structural designs for an estate at Elegushi in lekki. And the Owner insisted I reduce the raft to 750mm depth. But based on my designs, 750 depth will fail. So I didn't. By the time they the foundations were done to my standard, as soon as the ground floor slabs were completed, heavy rain fell and the ground floor of many estates around the site were submerged, all the ground floor of all his own estate were not flooded.
That was when he knew I did a good job for him.
Apart from flooding, the ability of the foundation to carry the dead and imposed loads for at least 100 years is what is critical.

This should be done before laying of reinforcement. Reason being that when casting is done, the wet concrete usually slip through those holes thereby weakening the lower part of the slab which is subjected to tensile stress. But due to the leakage of the concrete at that bottom, what plasterers usually do is to fill it with mortar before plastering suffix of slab. But don't forget that the reinforcement were exposed before. So structurally, the bottom reinforcement is nonexistent. So when there are tensile forces, the slab cannot withstand them and what do you get? CRACKS!!! Then your fine POP starts cracking, blocks starts detaching at first floor and even crack etc.

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ghettodreamz:


What a question

BTW, Aso Rock was built by Mr WHO.

Goahead:
How much is a bag of cement sef?

Eragablessen:
Bless you op for a demanding thread like this. I've bought a land but plans to start my building by Feb. 2016.
The structures i hope should include 3 bedrooms, 2bathrooms and toilet each, 1 living room/kitchen, 1 dining room, small utility room and a gym room. I also want a "p.o.p" bent on the living room. Please do you have any idea on how i should go with the plans so as not to avoid architectural errors Thanks.
Modified, its going to be a flat pls...

You didn't state your own design depth and the no of storeys of the building or type of building. This would have helped more in forming a discussion.

Why didn't you reduce to 750mm as the client wanted? Is it because the building cannot be designed with such depth? Or because you need the building to be above the flood level as you say?

What parameters did you use to design the foundation to take care of the flood? Can you take us through the process?

ghettodreamz:


T for Thread

manwonder:
more

pure2012soul:

Can I get an answer to my question?

ghettodreamz:


What a question

BTW, Aso Rock was built by Mr WHO.

400billionman:


Use a good builder nah..

You cannot build yourself without requisite experience.. Location ?

opalu:
I have been involved in the structural corrections of more than 1,250 buildings that were wrongly built in the past 10 years.
In all, I have discovered the major reasons why buildings fail structurally are
1. Lack of professionals on the project. The some sub reasons that owners give are that they don't have money to pay them since their charges are avoidable. And also that they themselves have ideas about buildings etc. When there are no professionals on the project, such project will not have the necessary CORRECT designs/drawings. Such projects won't have the right professionals Supervising the Construction Process.
2. Another major reason for Structural failure and foundation issues is the use of substandard materials. These include reinforcements, Sharp sands, Granites, Cement even Water etc. So many Rebars being used can easily cut or rust. Water that contains impurities is not safe for concrete a since those impurities attack the concrete. (Chemistry 101). A Man wanted quote one day and I gave him. But he went for one desperate Contractor who used filling sand to cast concrete! After 6 months, the suspended slab (decking) started vibrating like water bed. I was also called upon and i corrected it at a cost 3 times the cost to build a solid slab. In addition, using the same size of granite (coarse aggregate ) can weaken the concrete.
3. Another reason for failure in buildings is the use of wrong methodology in construction. For instance there is a method whereby wet concrete is vibrated in order to expel voids and holes inside. If you are using pole vibrator, it has to be poked into it left in there for brief interval and removed and poked somewhere else. Some quack roadside casters just use stick to shook here and there or hit here and there. Even if the vibrating machine is used wrongly, it will trap voids. Every construction work has best practice that if not followed, the result will be bad. Another example is that when a carpenter lays the 1x12 for first floor slab, every hole between the planks must be covered with well sliced cement bags nailed with tiny nails. This should be done before laying of reinforcement. Reason being that when casting is done, the wet concrete usually slip through those holes thereby weakening the lower part of the slab which is subjected to tensile stress. But due to the leakage of the concrete at that bottom, what plasterers usually do is to fill it with mortar before plastering suffix of slab. But don't forget that the reinforcement were exposed before. So structurally, the bottom reinforcement is nonexistent. So when there are tensile forces, the slab cannot withstand them and what do you get? CRACKS!!! Then your fine POP starts cracking, blocks starts detaching at first floor and even crack etc.

Let me stop and await your questions.

TYTAN:
@ Opalu: good work. i have just plastered my 3bedroom twin duplex and after a while i stated noticing tiny cracks here and there on the walls. i inquired from the structural engineer what could have caused the cracks, he said the house have just began to settle. can you please give a candid opinion on this. Thank you

Goahead:
How much is a bag of cement sef?

Goahead:
How much is a bag of cement sef?

eminemkayc:


I cannot precisely hold brief for the original poster, however, raft foundations (beam-raft in the poster's instance, i presume) are generally used where poor cohesive/organic soils are encountered, loads from superstructure are not too heavy and settlement (consolidation and creep) are to be controlled. The 750mm firstly, i guess, should be the depth of the raft's ground beam. Secondly, the increase in depth away from 750mm, definitely, is not as a result of the in-ability of a 750mm deep beam to resist bending and shear stresses as a result of loads from the raft but should be as a result of the ground water conditions, which the engineer (op) anticipates would rise above its present condition.

pure2012soul:
I intend putting up a 4 bedroom bungalow on a plot that measures 100x100. It's on a rocky but flat land. The design includes a laundry room, a pantry attached ti the kitchen and all rooms ensuite. Also, there's provision for a walk-in closet in the master bedroom. What sort of foundation should I go for and the likely cost implication?