Setting contingency and uncovering hidden costs for a 150 m² Jakarta renovation

L

LuckyCedar

Property investor
Keeping the full design risks squeezing the reserve, while cutting it now could remove things that prove affordable once the house is opened up. I am working with a preliminary IDR 5,950,000,000 budget for a 150 m² country home renovation in Jakarta.

The planned work includes kitchens and bathrooms, floors, decoration, electrical inspection and some energy improvements. There is no extension, although existing structural defects would still need attention. Before fixing the scope, what level of contingency would you hold for moisture, hidden services and remedial work? I would also like bidders to identify exclusions, sequencing assumptions and materials with long lead times.
 
I would initially reserve around 15% outside the working construction budget, rather than letting it become money available for upgrades. Before pricing, ask for investigation of moisture sources, plumbing routes, the electrical installation and any visible structural movement. Every contractor should also state assumptions and exclusions for demolition, disposal, access, temporary protection, testing and making good.
 
How old is the house, and will it be occupied during the work? Also, do you have reliable drawings showing plumbing and electrical routes? Those answers could change both sequencing and contingency. I would want the roof, external drainage and wet-area walls examined before approving new flooring or cabinets, otherwise a moisture problem could be covered rather than resolved.
 
I’m less convinced that choosing a contingency percentage first is the answer. If the scope is still described as “electrical checks” and “moderate energy upgrades,” quotations may include completely different work. Define what triggers replacement, which rooms are being rewired or replumbed, and exactly which energy measures are included. A vague scope can consume any contingency.
 
That is fair, but some items cannot be fully defined without opening walls or floors. I’d separate known work from provisional allowances for concealed plumbing, damaged substrates and electrical faults. Charlotte should also ask who handles permit timing, whether approvals are assumed in the programme, and which materials must be ordered before demolition starts.
 
Agreed on separating allowances. I would sequence it as investigation and selective opening first, then moisture and service repairs, followed by any structural remedial work, wet areas, energy measures, finishes and final testing. Ordering the kitchen early may help lead times, but final dimensions should wait until walls and floors have been opened and corrected.
 
The energy scope needs to follow the condition findings rather than run alongside them. Sealing or lining an area before understanding moisture movement could create expensive rework. Ask for each proposed measure to show the affected rooms, required preparatory work, interaction with ventilation or cooling, and how performance will be verified. That makes it easier to remove low-priority measures if the hidden-condition allowance is needed.
 
I’d lean closer to 20% until the invasive investigation is complete, then reduce it only when the unknowns have genuinely been priced. No extension does not mean no structural cost: existing movement, roof defects or rotten concealed material can still affect the renovation. The size of the overall budget is not protection against incomplete scope.
 
When tenders arrive, compare them line by line rather than by total. Require separate figures for demolition, electrical, plumbing, moisture repairs, kitchen, bathrooms, flooring, painting and energy work. Ask each contractor to list owner-supplied items, taxes, supervision, waste removal, protection, testing, permit responsibilities, payment stages and material substitutions. Unpriced blanks should not be treated as included.
 
The line-by-line tender comparison may expose another issue: should finishes be selected before the concealed risks are priced? I would pause those choices and use the same written scope for every bidder, backed by a condition survey and limited opening-up where moisture or services are most uncertain.

The programme can allow for permits and long-lead items—for example, ordering cabinets only after wet-area problems are understood—without fixing every installation date. If the resulting prices are too high, reduce finish specifications before removing necessary structural, moisture, electrical or plumbing repairs.
 
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