Hi all,

I need to extend 5" at the back of my DSL house for a wet kitchen and the soil at my area is soft. Neighbouring house extended but cracks is happening within a year or 2.

The contractor recommended to do a RC piling. Price quoted as follows:

Concrete piling with concrete bar 20ft, 30pcs - RM13.5k

i was surprised by such a high price. so would like to know if this is a reasonable market price?

also he informed that if i don't need to use so much piles, the remaining are not refundable not sure if this is the market practice?

the extension is only 5'x20', single storey.

thanks in advance

This post has been edited by @lowyat: Sep 19 2022, 06:25 PM

I remember someone quoting around RM200 per pile. Sarawak.

Assuming 3x 6m 150x150 piles per point, that's about 10 pile points. Need that many for a 100sf extension?

Also, how deep is the estimated point? if say 14m, then cheaper to get 6+6+3 vs 3x6m (more wastage).

Piling equipment is heavy and cumbersome. Mobilizing and demob costs money. Cheaper per pile if do more points/bigger projects.

150x150 pile per length 6m cost bout rm160-170
200x200 pile per length 6m cost bout rm200-210

but usually those price for full load lorry, which cost 2000-2500 per trip

so not sure if your price includes workmanship (mob & demob, handling & pitching, driving of piles) easily another 8-12k for such small area

u can try bakau pile option if your soil condition is not too bad

thanks for the info. yes i believe the price is including mob/demob, installation, etc. as it's the lump sum price from the contractor.

btw he also said that if there are remaining piles unused, normally they will not be returned and thus no reduction in price will be expected. not sure if this is normal or it's due to the transport cost is high and not worth it to return?

u r right, normally if not alot piles left, no return, even for our project left over 50+ piles, can’t be returned…

as mentioned i think whether is worth have to depend on your soil conditions…if your area is klang, better not risk it

if other non near river area, u can do a soin investigation test, cost another 2-3k. if soil is solid, raft foundation might be sufficient

ya it's at Klang, the soil is quite bad as claimed by the reno contractor, as my house is at the "fill" part and normally the compaction is not done properly by the developer.

we managed to see the SI report from the developer, it's something like this (they didn't provide the hardcopy though)

- backfill: 3m
- clay: 9m
- sand/silt: 5m
- below that is the sandstone

from your experience, do you think it's something that require RC piling? and does it means that most likely i need to pile down to about 17m (3+9+5) to set?

i read from google, some say can do raft foundation, but i think the contractor is not familiar with this. do you think if raft foundation can be a cheaper option?

thanks

This post has been edited by @lowyat: Sep 22 2022, 09:27 AM

raft foundation is definitely a cheaper option than piling

but i would not advise raft foundation seeing your area is klang, clay/sand/slit is usually very soft, to have a more accurate idea, your SI report shud mention N values at a column, anything <25, piling is preferred

Klang area..

Clay - 9m

Sand/slit - 5m

Looks like it's your house soil foundation is just so so only...

Don't cut cost on the RC piling... And use cheaper options...

1. Maybe your requirement of ‘No Crack’ scared the hell out of the contractor which they suggest the most expensive foundation method for your extension. Do note most of the extensions would probably crack in time to come due to differential settlement from different foundations at a different timeline.

2. It would be a great laughing stock at the fraternity of the construction industry for a single storey building to have piling foundation for its base. Why ? Cost is expensive and does not justify the return of value.

3. The most economical advice I can give is for you to forgo the piling foundation but to use the raft foundation and connect to your existing structure using post-installed rebar (google HILTI post-installed rebar)for your single storey extension. Surely will not avoid cracks entirely but an economical solution.

4. If you are still paranoid, then you can add bakau pile to your raft foundation (which you can use a backhoe to drive in the bakau pile – cheaper than concrete piling) which most of the 2 storey houses in klang uses (see picture).

Many years back when I extended my first house in Setia Alam for an area of 18 feet X 11 feet using paya bakau. The extended area sunk and cracks as big as 2 fist. Demolished it and redo it the 2nd time and this time still with paya bakau with double the length. Still cracked at the end and gave up and sold back the unit to developer. I would recommend to spend some money on investigating the soil and maybe get a few contractors to give their quotes and approach to the implementation. For me, it's better to overdo rather than regret later as you would have spend more money in the interior later on.

thanks for the info.

actually i'm fine with minor hairline cracks like 1 or 2mm. but the neighbouring houses, some got cracks like 1 inch gap

about the option of using "HILTI post-installed rebar", may i know if need to see the structure design of the existing house first?

lucky you, the developer is willing to buy back