Please I need assistance from engineers in the house. A friend want to build a story building -5 bedroom duplex front and 3 bedroom flats at d back. The dilemma now is he contacted two engineers for quotes, one said he will use PILE Foundation while other said he will do RAFT Foundation.

The dilemma now is, who should he contract given that he want d best required foundation as this is key to a solid building. He also has no fund to waste repeating/correcting mistakes.

Pls he need ur candid advice and suggestions on this issue.

The land is in ogudu-ori oke area of Lagos a swampy area.

Bros with due respect you must be educated. So why this unnecessary confusion. The issue is as simple as ABC. Consult a geologists for soil test ! It takes less than 150k.although an experience engineer supposed to give advice on foundation to adopt but as confusion has set in.DO SOIL TEST

If its a swampy area I sugest pile foundation or better still seek d help of a professional quantity surveyor, it will save u future cost.

segcy.moor:
Bros with due respect you must be educated. So why this unnecessary confusion. The issue is as simple as ABC. Consult a geologists for soil test ! It takes less than 150k.although an experience engineer supposed to give advice on foundation to adopt but as confusion has set in.DO SOIL TEST

Learning is a continues thing as long as we live. The post is also intended to lead to further learning. So we are making progress. Thx for ur input sha.

hadbak: If its a swampy area I sugest pile foundation or better still seek d help of a professional quantity surveyor, it will save u future cost.

what has qty surveyor got to do with foundation type. Ogudu, mary land and anthony are the worst area of lagos
sate even pile that is not properly done fails. Pls contact a seasoned and reliable structural engineer who will in turn engage and supervise a geophysical engineer who will conduct a good soil test. The structural engineer will then determine the suitable foundation type and designed it fully.

Aventures: what has qty surveyor got to do with foundation type. Ogudu, mary land and anthony are the worst area of lagos
sate even pile that is not properly done fails. Pls contact a seasoned and reliable structural engineer who will in turn engage and supervise a geophysical engineer who will conduct a good soil test. The structural engineer will then determine the suitable foundation type and designed it fully.

Absolutely!

More input abeg

Ok

Op,
Segcymore and aventures have said it all.

Abt to commission a soil test, will come back with the result when out.

Wht do one look out for when doing soil test.
Everybody claims professional atimes is difficult to differentiate quack from pro.

ensure u re there when d test is to be done and equally insist that the report is certified by a registered geotech professional or coren registered structural engr. also ensure that the d certifier licence is up to date. this same process is what d telecom industry engage during desgn stage

Aventures: ensure u re there when d test is to be done and equally insist that the report is certified by a registered geotech professional or coren registered structural engr. also ensure that the d certifier licence is up to date. this same process is what d telecom industry engage during desgn stage

Thanks
I understand the soil will be taken to the Lab for analysis. Being there wht do one check out for exactly?

Most people do not know who a Structural Engineer is. As a COREN registered Civil/structural Engineer who by His grace rounding-up his Doctorate (@Unilorin), I have sworn †̥☺ uphold and enlighten the society abt d profession wherever I find myself.

I"d be brief and simple fø̲̣̣я̅ now. Civil Engineering has many areas of specialization like: Geotechnics, Structural, Airport, Railway, Highway and Water (put 'Engineering at their fronts fø̲̣̣я̅ me).
As a Structural Engineer, you basically determine the load/forces/stresses via structural analysis and proceed †̥☺ carry out the structural design: whereby the Engineer selects the sizes, types, positions etc of the members †̥☺ use †̥☺ withstand the anticipated ultimate loads with respect †̥☺ relevant Codes taking account of necessary factors of safety and assumptions.

@ OP, when a Qualified and Experienced Structural Engineer takes the DRAWING of the Architect and evaluates the loads, the loads reaching the soil thru the foundation at various points may be 'heavier' than what the soil can bear (Soil Bearing Capacity). So he may advice †̥☺ use Pile foundation that use 'pillar'-like concrete members in the soil. These piles transfer the loads †̥☺ good bearing strata down inside d ground. I've done 1,500 piles of 24m average at Gbagada and even 33 m deep piles at Ikorodu (Agbowa). That was like height of 11 storey buildings inside d ground.
Now if the Structural Guy discovers that Ūя̲̅ site is not entirely bad, he can suggest solid raft or beam and slab raft like so many estates we have done at Lekki axis. What a raft does is †̥☺ spread over the good and bad portions of the land so that the effects of the weak portions of the soil are neutralized by those of the strong areas. Acts monolithically sort of.

In High-rise buildings, U̶̲̥̅̊ either use both piles and raft combined or U̶̲̥̅̊ go fø̲̣̣я̅ vibrofloatation as was used in many at Marina.

Let me explain briefly why a structural Engr shld be d one †̥☺ select a Geologist †̥☺ do soil test.
The report a Geologist produces is best understood by d Civil Engineer. Fø̲̣̣я̅ same reason a Doctor understands and uses the results from Lab technologist.

If U̶̲̥̅̊ meet someone by yourself, by the way U̶̲̥̅̊ talk, they know U̶̲̥̅̊ are a layman †̥☺ d field so they may send an unschooled but skilled guy †̥☺ do the test on site then copy and paste report of previous test carried out and submit †̥☺ you. But with a Civil Engineer with them, the actual situation of your site is known. (However, there are so many Geologists with impeccable integrity who will never copy and paste results).

When we say Soil Test, what is it self??
Answer:
The soil underground has different layers (strata) frm the vegetable topsoil down down down. If it is a CPT test or 'borehole' test, they reveal the different types, colour etc above all strengths (bearing capacities) of each layer as you go down. And at what depth is water found. A borehole (SPT) test goes deeper than a CPT. After a borehole test, it can be used as source of water fø̲̣̣я̅ d project.
Random positions are selected on site (spread out well) †̥☺ get a correct representative reality under the ground.
I did one in Ibadan and so that though the site was water logged (we found water at 1 m), the soil was as strong at 1m as 12m in a place in Kogi state.

One funny thing abt soil is that you next door naighbour may use Pad foundation or even Strip foundation dat is cheap, and crossing over †̥☺ your land, it is peat (decayed waste) without good soil till 20m depth. I've seen this many times.

I'd end by saying most times, people who buy already built buildings pay so high fø̲̣̣я̅ the foundations. A guy can build a N80m house in Bayelsa but another can build the same house for N40m. Foundation and management happeneth †̥☺ them all.

As several people have posted before me, "get a soil test done". Its the result of the test that would inform what kind of foundation can be built on the land.

Am here again! Good aftnun ma people!

Reserved

Anyone

I don't know.

Ask google. It'll give u d best answer

dats y i lov my fellow engineers dey can repp

Cypost: More input abeg

What else do you need? @segcymore and aventures have already answered you.

It is the soil test that will tell you the load-bearing capacity of the soil and the depth you should go for foundation.

Don't be like someone who, after hearing the truth, continues to hunt for untruth.

Aventures and opalu have said it all. Once fell into such error and the loss was colossal.
Most likely from experience on that area, pile will be used.

Answer


Don't confuse about raft and mat foundation. Raft foundation is mat foundation. Now what is raft foundation?


Raft foundation is a thick concrete slab reinforced with steel which covers the entire contact area of the structure like a thick floor. Sometimes area covered by raft may be greater than the contact area depending on the bearing capacity of the soil underneath. The reinforcing bars runs normal to each other in both top and bottom layers of steel reinforcement. Sometimes inverted main beams and secondary beams are used to carry column loads that require thicker foundation slab considering economy of the structure. Both beams cast monolithically with raft slab.
Now I shall discuss where raft foundations are required. Raft foundation is required where soils have low bearing capacity and have to support heavy structural loads. Normally structures on marshy land, soft clay and land that are made up of sanitary land fill or other materials (like debris, unconsolidated soil and solid waste etc. where differential settlement is suspected)-require raft foundation. Raft foundations are preferred in the soil that are suspected to subsidence. Subsidence may occur from different sources like change in ground water level due to climatic change specially in case expansive soil or foundation in mining area.
In one words, where deep foundation like pile foundation are not economical and feasible and isolated column footing is impracticable due to large footing size or over-lapping of neighbor footing , raft foundation is the economical solution.



http://civil-engg-world..fr/2012/06/what-is-raft-foundation-difference.html


Speaking as a Geological Engr.

The simplest answer is that raft foundations are advisable for use in areas like; Swamp land, areas susceptible to earth movement and areas with low bearing capacity.

The whole Idea behind the raft foundation is to distribute the weight evenly across the foundation as against pile foundations where you have main pillars|beams and smaller supports.

This is from my small understanding of Soil|rock mechanics & Foundation Engineering!


God bless Geologists!

@cypost I must say with authority that your search is over with this guy come in (oparu) I do advice you engage has he spoke but from wealth of experience. As a matter of fact what he said about copy and paste practice is quite right bco a geologist friend of mine has done similar thing for me. Engage him and I believe you won't regret

Is simple: get a good structural engineer that will design the foundation detail base on existing site analysis that can be gotten from public record or you conduct one yourself, it include soil test. This is done to be sure of the peculiarity of the local site.
Note: the idea of what foundation to use is a responsibility of the engineer: the contractor do their bid base on the design provided by the design team:

the engineer that quoted for pile foundation for a storey building is definitely a quack.... unless you are building an island in a river, Pile foundations are long, slender, columnar elements in a foundation that are installed into the ground.
They aretypically made from steel or reinforced concrete and possibly timber . A foundation is described as piled when its depth is more than three times its breadth.
Pile foundations are principally used to transfer the loads
from a superstructure, through weak, compressible strata
or water onto stronger, more compact, less compressible
and stiffer soil or rock at depth, increasing the effective size of a foundation and resisting horizontal loads

raft foundation is suitable for d design

Fadelex: the engineer that quoted for pile foundation for a storey building is definitely a quack.... unless you are building an island in a river, Pile foundations are long, slender, columnar elements in a foundation that are installed into the ground.
They aretypically made from steel or reinforced concrete and possibly timber . A foundation is described as piled when its depth is more than three times its breadth.
Pile foundations are principally used to transfer the loads
from a superstructure, through weak, compressible strata
or water onto stronger, more compact, less compressible
and stiffer soil or rock at depth, increasing the effective size of a foundation and resisting horizontal loads

raft foundation is suitable for d design

You sir have spoken like a true engineer...

Which engineering field do you rep sir?

Good post @Opalu. Just as Opalu has said if you cannot afford Pile foundation as suggested then go for Solid Raft which is cheaper.

.

D'Govnor:
Is simple: get a good structural engineer that will design the foundation detail base on existing site analysis that can be gotten from public record or you conduct one yourself, it include soil test. This is done to be sure of the peculiarity of the local site.
Note: the idea of what foundation to use is a responsibility of the engineer: the contractor do their bid base on the design provided by the design team:

For the purpose of being proper, a Structural Engineer should not be the one to design a foundation plan. Foundation analysis should ideally be done by a Foundation engineer. Its based on the findings of the foundation Engineer that the Structural guys would base their design.