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DaddyJP

Soil test analysis and piling

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Hi Guys,

Am rebuilding my home, just received approval from URA now proceeding to the next step of submission to BCA.

Just received good news from PE that piling is not required. Piling is replaced with "big footing".

At first, I was presently surprised and happy that piling is not required, as this would mean a huge saving on $$ and also time. 

But my happiness proves to be shortlived as soon after I received call from the contractor that he needs to add cost, $60k, for the "big footing".

Need some advise here:

1. what is the different between piling and footing? 

2. Should be worry about the structural integrity of the house as the soil test report clearing stated piling is recommended?

3. Is $60k reasonable? Should I even agree to the cost increase as the footing is considered as part of the contraction cost that is covered by the agreement/quotation with the contractor.

Thanks!

 

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Did you hire an architect or yours is a design and build contractor?

check your contact with the builder and see the details on whether piling cost has already been covered in the contract you signed. If nothing has been signed then of cos the builder can adjust his cost for the contract. 

footings are big blocks of reinforced concrete with rebars inside sitting on the soil and these rebars will later on be joined to the underground beams to provide the foundation for the house. Piling is using piles driven into the soil until the piles reach the hard rock/soil layer and later on pile caps(similar to footings) are cast on top of the piles.

there’s nothing wrong with using footings as foundation. The PE would have done all his calculations based on the soil investigation report and determined that footings will work well. My own house is built on footings as well. 
normally the PE should request for a plate bearing test once the house is demolished to verify and confirm that the house can be supported by the soil using footings. This test results need to be submitted to BCA and if the test passes, then there’s nothing to worry about using footings. 
 

as mentioned, check your contract/quotation with the builder. Normally foundation( footings, underground beams) would be classified under substructure. If cost had already been allocated for this in the original quotation, then the builder shouldn’t add on the 60k. But if nothing had been confirmed for this part, then 60k seems to be a fair amount in current context
 

 

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Hi Snoozee, 

Was hoping to hear from you. Thanks for the quick response as always.

I did not hire architect but engaged a design-n-build contractor to build my house with land size 1800sqft.

The contract specifically stated piling work is excluded. What has been included in the structural works in the contract for the 1st level is column stumps, column & stittiners, RC ground slab, RC column and RC structure for footing which also include formworks and raft foundation. Sounds right?

For a land size of 1800sqft land, is $60k for the construction of the footing reasonable?

Thanks 

 

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48 minutes ago, DaddyJP said:

Hi Snoozee, 

Was hoping to hear from you. Thanks for the quick response as always.

I did not hire architect but engaged a design-n-build contractor to build my house with land size 1800sqft.

The contract specifically stated piling work is excluded. What has been included in the structural works in the contract for the 1st level is column stumps, column & stittiners, RC ground slab, RC column and RC structure for footing which also include formworks and raft foundation. Sounds right?

For a land size of 1800sqft land, is $60k for the construction of the footing reasonable?

Thanks 

Your contract already catered for these items “RC structure for footing which also include formworks and raft foundation” which should form the footings and foundation already. So best is that you clarify with the builder on what these items are and the difference between these and the new footings they are charging you. Even if the new footings are larger than intended, it shouldn’t cost an additional 60k. 
 

I guess this is the risk you take when engaging a design and build contractor rather than going the architect route. With an architect, everything including structural design would have been confirmed before hand and the awarded contract would have no variations unless something unexpected happened or owner requested for changes. 

 

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The contractor explained that the new footing is 3x bigger than originally quoated. 

Too late to back to the archi route now. 😅

 

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1 hour ago, DaddyJP said:

The contractor explained that the new footing is 3x bigger than originally quoated. 

Too late to back to the archi route now. 😅

Unfortunately you are at the mercy of your contractor now. So if you are unwilling to pay for the additional cost, you are just stuck with no way to move forward unless you want to terminate his contract and find someone else to take over and such. 
 

I don’t know how many footings you have for your house has but assuming there are 10, each footing will cost an additional 6k.

For my house, I had to enlarge 2 of my footings and corresponding underground beams and I had to pay about 8k for this.

 

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I did not go to the archi route because I found that the architects I talked to mostly recommended contractors that they know or familiar to come for the bidding, thus did not also provide the confident I needed. Coincidentally I found this contractor of mine who is an honest man, visited quite a few of his building sites and I liked what I saw.

Yes, you are right without the architect, there is no one to check and balance in situation like this.

Back to this case, he explained the $240k quoted for structural works for the 3 levels + attic inter-t with total buildup of 4000sqft did not include the footings (as shown in the drawing attached) as he assumed piling would likely be needed.

He estimated that those footing as indicated by the arrows would required 3x more cement and rebars as compared to what he has quoted for the structural works. He said that the actual cost increased would likely be more than $60k in today's Covid context.

Sounds reasonable?

 

 

Screenshot_20210529-152928_WhatsApp.jpg

 

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Hi may I check how long did you have to wait for soil test appointment? Anyone knows if we can  arrange for our own soil test ? Or needs to be via QP 

 

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14 minutes ago, Alkft said:

Hi may I check how long did you have to wait for soil test appointment? Anyone knows if we can  arrange for our own soil test ? Or needs to be via QP 

You need to have at least a PE who will determine the scope of the soil investigation. I sourced for my own SI company based on requirements specified by my PE. Also where to drill and when to stop drilling is also based on the PE’s instructions 

 

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24 minutes ago, DaddyJP said:

I did not go to the archi route because I found that the architects I talked to mostly recommended contractors that they know or familiar to come for the bidding, thus did not also provide the confident I needed. Coincidentally I found this contractor of mine who is an honest man, visited quite a few of his building sites and I liked what I saw.

Yes, you are right without the architect, there is no one to check and balance in situation like this.

Back to this case, he explained the $240k quoted for structural works for the 3 levels + attic inter-t with total buildup of 4000sqft did not include the footings (as shown in the drawing attached) as he assumed piling would likely be needed.

He estimated that those footing as indicated by the arrows would required 3x more cement and rebars as compared to what he has quoted for the structural works. He said that the actual cost increased would likely be more than $60k in today's Covid context.

Sounds reasonable?

 

 

Screenshot_20210529-152928_WhatsApp.jpg

Architects would usually find 3 to 5 contractors to bid for the job. Of cos there will be contractors whom they had worked with before on previous jobs who are invited for the tender. Look at it this way. If the contractor isn’t up to par previously, would the architect invite him to bid for another job? The architect also won’t want problems with a problematic contractor as well right?
 

honestly speaking, if the contractor has not meant to include foundation work in the original quotation, then all the items related to foundation should not be in the quotation in the first place. It’s like you go to a showroom to buy a car, then you want to upgrade to bigger rims and tyres and the car dealer tells you that the original quotation for the car didn’t cater for rims and tyres. 
 

if the contractor says the new footings are 3 times larger then original then I would ask for the original drawings to see what was the original estimated footings size. It is easy to calculate the additional materials required when you have the original and new structural plans to compare with. 
 

as mentioned, you are at the mercy of your contractor now. Whether the additional cost is reasonable or not doesn’t make a difference since you have signed the contract and such and don’t really have any other options to move forward besides accepting this new extra cost. 

 

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It is so strange that the contractor can just quote for the structure above the foundation only.  Just like buying a brand new car without the wheels.  Very strange.

Edited by tayv
 

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If engage with D&B contractor, foundation work will likely not included in the quotation as at the time of signing the contract with the contractor, the type of foundation suitable for your land is not determined yet. 

Only after Soil test result is available and PE hired to do the structural design/calculations would you know the foundation type, I.e. piling or deep footing (like my case) to support the columns and cross beams or no need if the soil condition is solid like in the Bukit Timah area.

My place is just beside a river and sure enough the soil test result mentions piling is needed. However my contractor specifically requested the PE to check whether piling can be avoided, because the piling cost is very high (saw a quotation $130k to 150k for 36x piles by micro bore) and piling service is very difficult to secure because of Covid (want to pay also cannot get). In conclusion, the PE delivered good news to me which turned out to be bad news to him.

I hv no problem to share the cost with my contractor, just trying to find out what is the fair price from the good guys in this forum

 

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I am not sure why D&B contract excludes foundation works.  The potential builder can just hire a soil investigation firm to do the soil investigation and include the foundation cost in the contract.  Even the potential builder does not get the job in the end, he can always claim back the soil investigation cost from the owner.  Very strange.

If the soil Investigation report recommends piling (the report is endorsed by a PE), I am not sure why the builder’s PE would choose to adopt shallow foundation.  If the site is next to a river, chances are that there are soft soil with low SPT at the uppermost layers closer to existing ground level.  Hence, bearing soil will yield lower bearing resistance which gives rise to the need to have big shallow foundation.  

As for piles, bored micropiles are the more expensive piling system.  Precast concrete pIles or steel H-piles can be installed using jacked-in system which is much more affordable.  

Just my 2-cent worth of opinion

Edited by tayv
 

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2 hours ago, tayv said:

I am not sure why D&B contract excludes foundation works.  The potential builder can just hire a soil investigation firm to do the soil investigation and include the foundation cost in the contract.  Even the potential builder does not get the job in the end, he can always claim back the soil investigation cost from the owner.  Very strange.

If the soil Investigation report recommends piling (the report is endorsed by a PE), I am not sure why the builder’s PE would choose to adopt shallow foundation.  If the site is next to a river, chances are that there are soft soil with low SPT at the uppermost layers closer to existing ground level.  Hence, bearing soil will yield lower bearing resistance which gives rise to the need to have big shallow foundation.  

As for piles, bored micropiles are the more expensive piling system.  Precast concrete pIles or steel H-piles can be installed using jacked-in system which is much more affordable.  

Just my 2-cent worth of opinion

Soil investigation needs to be done based on instructions or requirements of a PE. So need to find a PE first and then find the SI firm. 
Yes you are correct that the potential builder can do the above first. But why would one want to spend time and effort to do something if he is not going to get the job in the end even though the builder could have quoted for just this scope of work?

In the usual architect route, the architect is appointed and the PE appointed as well. Then the SI company is appointed and takes directions from the PE. Once the SI report is out, the PE designs the structure and the architect will call for tender based on the confirmed architectural and structural plans. In this manner, cost is confirmed and controlled right from the start and there should be any additional costs incurred unless something unexpected happened or owner requested for changes. 
 

the location and surroundings of the site usually only provides an estimate and is not a confirmation on what type of foundation can be done. One member had gotten an estimate from a builder as his site is near low lying area. Builder said need piling but the house ended up doing raft foundation as the site is on a high point near the low lying area. My own house is located on high ground. But I had to do footings as the original site was excavated massively when the whole area was developed and the developer back then backfilled the area with clayey soil.

ultimately what type of foundation to be built is decided by the PE as he is the one who is putting his license on the line when the structural plans is submitted to BCA. We as layman can’t dispute the PE’s decision unless we get another PE to provide another opinion. 
 

 

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