YES YES YES, we have a winner, this is the correct way.

First I talked only about footing, not column. First thing first, are you disputing the suggested footing?

2nd, whether it is footing or specification for columns what you suggest TS to do? Hire engineer? Yes, that is the right way to do but that is a bomb to pay. There are shortcuts and alternatives and am suggesting if you cannot go by air go by sea, something like that. Shortcut sometime is even better and more effective, save time and effort and money.

There are many ways of solving a problem when we think out of box especially when the cost of doing it "correctly" is beyond reasonable as far as price/cost is concerned in this case.

One other think out of box or shortcuts is go to the developer and look for the architecture or structural drawing and follow. Another place to get such information is from the land office or local council (am not sure which one). The authority should have such information or request such information when approving housing projects.

So, hiring an engineer is also not a definite answer compare to what has been done by the developer more thoroughly done, than one personally hired engineer, in a big or bigger project of many houses.

It is healthy to dispute and everyone learn from each other. I was not thinking of column but only footing which is only a part of the whole reno consideration.

Cheers

sydneguy, i respect ur view. tq for ur view. part of knowledge sharing i learn.

This post has been edited by aquaria87: Nov 15 2013, 11:56 PM

For small reno job, i dont think ppl willing to pay profesional engineer to design such simple footing. maybe for deep pocket ppl can la..but for ppl like me... it is based on contractor experience and also neighbour reno works cud help for contractor to design the footing. A lot of reno works has been carried out this way and to b surprise those indon workers are sometime much brilliant and creative to solve design problem as they are more practical guy....

I accord ur view bro... even engineer design are sometime has flaw bcoz they depend on what ever data they have. i cant imagine to do small reno job u hv to fork out so much money to engage profesional engineer...

Nice to read all of your ideas and opinions.i think get structural drawing from developer is a good idea.however,can we request from developer n will they give it to us?

New house? How long has it been. If too long time ago the developer dont give a damn to dig the files.

When your house is at hill cut area, the area has to be left 10 yrs to subside and pilling needed. Usually you can see your next neighbors are you next to one that is lower than yours and how high is yours? Or the back of your house is hill or the front of your house is higher? Then you can guess if pilling is required or not. Pile only for the column. Footing no need to pile.

Like I said dig the existing footing where you want to extend and follow accordingly.

One other way for column is to dig deep and wide till you hit hard ground, concrete cement, sand and stones are cheap, after all you need only 2 or 4 column max.

If the extension is not a big area, on top of the footing, reinforced concrete the whole extension area like a slab. As such when the extended structure were to sink or subside it has to sink the whole reinforced area.

Just visualise yourself. A table with 4 feet on a sandy area, at a beach. You sit on top and another man also go on top. All the 4 feet sink into the sand. When you put the table upside down you and one other man stand on the upside down table, what happen? The table will not sink into sand as it now has big big surface area on the sand. Another 2 men go stand together or even 6 men altogther, no problem!!!! Make the reinforced concrete normally 6 inches thick, make it 8 if you want to.

Most people think, to hire an engineer is a waste of money. In this case, it maybe right if u r lucky, if u r not lucky enough, you will end up spending much more. I've seen so many failed reno, from 2 inch crack till the owner need to redo d structure all over again including d existing structure. All this are due to foundation settlement. What can u do then if that is hapening? Replaster the crack? It will reappear in no time unles u do something to stop the setlement. But d qn is how? pray to god? Redo d foting?

If owner dont have money, why renovate ur house from d first place? In this case, sinbe its a double story, I strongly advice, if u want to do it, please do it properly, let the prof do their job fist. Dont solely trust d indon, they dont even learn physics. Even u go to court u have to hire a lawyer, if u sick u seek doctor. Yes u can straight go to court to defend ur self, n u can straight away go to pharmacy to buy medicine. But.. know what i mean.

You are right, want to do do it properly, but hiring an engineer is only partly correct and may be a waste of money as nobody is checking on the work of the engineer. There is no check and balance. The major part of it is construct it correctly.

Cracks. When we talk about crack, where the crack is? Crack is not always due to subsidence. The most common problem with crack is Cold Joint and shrinkage of new concrete. What appear of a crack between the existing main building and the new extension usually is due to poor joint. As concrete cure (especially the first year) is shrink alot. As it shrink it is pulling themselves together, as such it is pulling away from the existing new building and so cracks appear there. This is only one of the reason concrete crack there due to poor cold joints. It has nothing to do with subsidence. The proper way to prevent such crack is to dig out the existing main building rebar from its beams and columns and hook join to the new concrete rebar then pour concrete. When concrete set or cure over the years as it shrink, due to the hooking of the rebar the existing building is holding the new extension from pulling away and therefore no crack at the cold joints.

There are other types of crack which also got nothing to do with subsidence or due to new extension foundation sinking/subsidence. The foundation, footing and column and beams are hook together in concrete as one piece but not the brick walls and if cracks appear between this one piece and the walls then it is due to, again, poor cold joint between them. such cracks usually appear at the top of the brick walls and beam due to wall concrete shrinkage and gravitational pull. Less obvious is the crack along the column and brick wall, and again this got nothing to do with sinking.

Why spend your money on a "suspicious" engineer (suspicious because no check and balance) when it is so much cheaper to build a slab (called slab foundation) reinforced with the footing as one single piece and yet much secure foundation

See pic of a slab foundation


This post has been edited by stevie8: Nov 17 2013, 02:32 PM

Did u mean raft foundation?. 2 inch crack will never caused by shrinkage. U ask any expert, he will agree wt me. I learn this from an structural expert.

Although u choose a raft foundation, u still need an egineer to calculate the slab thickness, rebar size n its location.

Any way, are u an engineer urself.

Wah. Which engineering code u r using bro? BS or ASME?

There is no need to be sarcastic. If you are so called expert give your valuable comments. When you are not a doctor do not talk like one as though you are, okie

Here we talk so that people can understand the logic. There is no need for an engineer trying to frighten others. Even with engineer calculation still many buildings (not extension,OK!) has more than 2 inches crack and some of it you can put your hand in. There is major problem with soil and the engineers failed to notice that. Do you also know that our twin towers is now not at its original site due to extended studies of the soil deep underneath that were not suitable?

This is extract from this website

http://civil-engg-world.blogspot.com/2013/...ONAS-Tower.html

"....The geotechnical survey discovered that the actual construction site was situated partially over decayed limestone deposition and rest over soft rock. After discovering this, the structure was relocated to avoid limestone deposition. The whole foundation was rested on 104 piles. To reach safe bed rock the piles were extended to depth ranging from (200-374) feet. To reach this depth, PETRONAS Tower became the structure having the deepest seated foundation of the world....."

So, having your house extension do you think you should do a extended study like our twin tower??? Small issue going beyond what is necessary. The answer my fren is you dont even for building a housing estate with landed houses and apartment blocks.

Do you see people extending thier house bring along load of concrete to test the foundation? You dont, ok! It costs you a bomb or the whole renovation cost by doing so!

I just wonder what the engineer will do and what test he will conduct and by the way you got a house? Your parents got. So you or your parents did any extension to the house and called an engineer to do it?

This post has been edited by stevie8: Nov 17 2013, 06:44 PM

When I said slab foundation so people know what it is. If I were to say raft foundation, many would not know what I was talking about. Understand this brother. Here extract from the same website and if you worry do this than to hiring a engineer. Money wisely spent on your extension than paying the engineer. See the last line, it is economy having this type of foundation and strong.

"...Raft foundation is a thick concrete slab reinforced with steel which covers the entire contact area of the structure like a thick floor....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...."

This post has been edited by stevie8: Nov 17 2013, 06:56 PM

Simple rule of physics pressure = force / area...the larger the area...the less pressure is asserted cos it is spread over a larger area.

Wah. So expert.. so much enginering knowledge, but ur reference is from blog spot?

Never mind, bro. Am not here to show off my knowledge. Am just wanting to help.

Here you go. For those who over worry too much and wanting to hire engineer and no such budget do a slab foundation. (I prefer to use the word slab) Your pilling or column no need to be big and deep hitting hard ground.

Again, if the sand is 10 feet deep and your table is 3 feet high, 2 men keep jumping on top of the table the 4 legs will go deep into the sand until it hit the top of the table. When you put the table upside down, 6 men keep jumping until the cow comes home, not an inch of the table face will sink into the sand! That is slap foundation.

Cheers