Short answer: there is no cheapest contract type. There is only who carries which risk, and every risk you hand to the contractor comes back to you as a contingency in the price. The real decision is not lump sum versus cost-plus. It is how complete your drawings are — because a fixed price is only fixed if the scope is.
Article 1724, Civil Code. A contractor who undertakes to build for a stipulated price, in conformity with plans and specifications agreed with the landowner, can neither withdraw from the contract nor demand an increase in price on account of the higher cost of labor or materials — unless there has been a change in the plans and specifications, and that change was authorised by the owner in writing, and the additional price was likewise fixed in writing by both parties. Cement getting more expensive is not a change in the plans.
| Lump sum | Cost-plus | Labor-only | |
|---|---|---|---|
| You pay | One fixed price | Actual cost + a fee | Materials yourself + labour price |
| Who buys materials | Contractor | Contractor, billed to you | You |
| Price escalation risk | Contractor | You | You |
| Wastage & pilferage risk | Contractor | Mostly you | You |
| Scope-change risk | You, at their rates | You, at cost | You |
| Needs complete drawings | Yes, absolutely | No | Yes, for the labour scope |
| Your time commitment | Low | Medium — you audit invoices | High — you run procurement |
| Cost certainty | High | Low without a GMP | Medium |
| Best when | Drawings are final | Scope is genuinely unknown | You have time and a good BOQ |
Same job, three structures. The differences come from the contingency a contractor prices into a fixed sum, the markup on materials, and how much your scope is going to move.
One price for a defined scope. The contractor absorbs material escalation, labour productivity and their own mistakes — and prices a contingency for all of it. That contingency is not greed; it is the cost of the certainty you asked for.
Lump sum works when the drawings are finished. It fails, expensively, when they are not — because every change becomes a variation priced without competition. You had three bidders when the contract was let. You have one when you decide to move the kitchen.
Article 1724 Cuts Both Ways
The written-authority rule protects owners from casual escalation: higher cement prices are not a change in the plans, so they are not grounds for an increase on a stipulated-price contract.
But it protects owners only if the paperwork discipline is real, and it exposes contractors who work on trust. A contractor who builds the extra room on a verbal instruction carries the risk of never being paid for it. The habit that protects both parties is identical: no change starts until the scope change and its price are both written down and signed — however small it seems at the time, and however awkward it feels to ask.
You reimburse actual cost and pay a fee, either a percentage or a fixed amount. Nobody prices a contingency for unknowns, because nobody is carrying them — you are.
It is the right structure when scope genuinely cannot be defined: renovation and retrofit where nothing is known until the wall is opened, or emergency works that must start before design finishes. It is the wrong structure when it is chosen simply because nobody wanted to finish the drawings.
You buy the materials; the contractor supplies labour, supervision and tools, usually priced pakyaw per unit or as a lump sum for the labour package. On a materials-heavy job you remove the contractor's markup on more than half the cost, which is genuine money.
What you take on is the entire procurement function: ordering to a bill of quantities, scheduling deliveries so the crew is never idle, receiving and counting, storing and protecting, and absorbing every over-order and breakage. Without a proper BOQ this arrangement fails, because you have no basis for knowing what to buy or whether what arrived matches what was needed. It also fails if you have a full-time job and expect to manage it by text message.
Two Different Things Called "Labor-Only"
In construction trade usage, a labor-only contract means the owner supplies materials and the contractor supplies labour. That is a pricing structure.
In labour law, labor-only contracting is a prohibited arrangement under the Labor Code, where a contractor merely supplies workers without substantial capital or investment and those workers perform activities directly related to the principal's business. Same words, different question.
Worth knowing: DOLE Department Order 174, series of 2017, expressly does not govern contracting in the construction industry under PCAB licensing coverage. Construction is covered instead by D.O. 19 s.1993 on employment of workers in construction, D.O. 13 s.1998 on construction safety and health, and the 2011 joint administrative order. Whether a specific arrangement is lawful turns on its facts, not its label — so take advice on the engagement rather than on the name.
Two obligations sit outside your choice of pricing model:
Articles 1723 and 1724 are provisions of the Civil Code of the Philippines; the D.O. 174 s.2017 scope point and the construction-industry issuances are DOLE department orders. The percentages in the calculator — contingency, fee, variation markup, wastage — are planning assumptions, not published figures, and vary widely with contractor, project and market. This article is general information for owners deciding how to structure a build. It is not legal advice, and whether a particular arrangement is lawful or enforceable depends on facts a general article cannot know. For a contract of any real value, have a lawyer read it before you sign.
Can a contractor raise the price of a lump sum contract in the Philippines?
Generally no. Article 1724 of the Civil Code provides that a contractor who undertakes to build a structure for a stipulated price, in conformity with plans and specifications agreed upon with the landowner, can neither withdraw from the contract nor demand an increase in price on account of the higher cost of labor or materials. There is one route to a valid increase, and it has two conditions that must both be met: there has been a change in the plans and specifications, that change was authorized by the owner in writing, and the additional price was likewise fixed in writing by both parties. Cement going up in price is not a change in the plans, so it is not a ground for an increase.
Is a verbal variation order enforceable in Philippine construction?
Article 1724 sets writing as the condition for recovering an increased price on a stipulated-price contract, both for the owner's authorization of the change and for the additional amount. In practice this cuts in both directions, which is why it matters to both parties. An owner who verbally asks for a bigger kitchen and then refuses the bill has a statutory argument. A contractor who does the work on a handshake carries the risk of never being paid for it. The professional habit that protects everyone is the same one either way: no change starts until the scope change and its price are both written down and signed, however small the item seems at the time.
What is the difference between a labor-only construction contract and illegal labor-only contracting?
They are different things that share a name, and confusing them causes real trouble. In construction trade usage, a labor-only contract means the owner buys the materials and the contractor supplies labour, supervision and tools, usually priced pakyaw per unit or as a lump sum for the labour. In labour law, labor-only contracting is a prohibited arrangement under the Labor Code in which a contractor merely supplies workers without substantial capital or investment and those workers perform activities directly related to the principal's business. The two are not the same question. Note also that DOLE Department Order 174, series of 2017, expressly does not govern contracting in the construction industry under PCAB licensing coverage; that is covered instead by D.O. 19, series of 1993, D.O. 13, series of 1998, and the 2011 joint administrative order. Whether any particular arrangement is lawful depends on its facts, so take advice on the specific engagement rather than on the label.
Which contract type is cheapest for a homeowner?
There is no cheapest type, only different placements of risk, and the placement is priced. A lump sum looks dearest on paper because the contractor includes a contingency for the risk they are absorbing, and it becomes the cheapest option when the drawings are complete and nothing changes. Cost-plus removes that contingency and gives you the contractor's actual costs plus a fee, which is genuinely cheaper when scope is uncertain, but it has no ceiling and requires you to audit invoices. Labor-only removes the contractor's markup on materials, which is real money on a materials-heavy job, but transfers procurement, delivery, storage, wastage and pilferage to you. The honest question is not which is cheapest but which risk you are best placed to carry.
When should an owner use a cost-plus contract?
When the scope genuinely cannot be defined in advance and a fixed price would therefore be a guess with a large contingency attached. Renovation and retrofit work on an existing building is the clearest case, because nobody knows what is behind the wall until it is opened. Cost-plus is also appropriate for emergency or remedial works that must start before design is complete. It should come with three protections that are often left out: a guaranteed maximum price so the arrangement has a ceiling, an agreed and audited definition of reimbursable cost, and open-book access to supplier invoices. Without those, a cost-plus contract is an open account with a percentage attached.
How long is a contractor liable for a building in the Philippines?
Article 1723 of the Civil Code sets a fifteen-year period from completion of the structure, and it divides the responsibility rather than pooling it. The engineer or architect who drew up the plans and specifications is liable for damages if the building collapses within that period by reason of a defect in those plans and specifications, or due to defects in the ground. The contractor is liable if it falls within the same period on account of defects in the construction, the use of materials of inferior quality furnished by him, or any violation of the terms of the contract. If the engineer or architect also supervises the construction, he is solidarily liable with the contractor, which is worth knowing on a design and build arrangement where one party does both. Acceptance of the building after completion does not waive these causes of action, and the action must be brought within ten years following the collapse.
Every argument in this article resolves the same way: a complete drawing set and an itemised bill of quantities. With those, any of the three structures works. Without them, none of them do.