A serious budget is not a number. It is a list of items with quantities, unit prices and a defined scope — and the difference between that and a one-page quote is most of the risk you carry.
Preliminaries and setting out; excavation and foundations; structure; masonry and slabs; plumbing, electrical, gas and air conditioning; waterproofing; renders, floors and paint; joinery and metalwork; glazing; bathroom and kitchen fittings; cistern, pump and tank; final cleaning and testing. Each with a unit, a quantity, a unit price and a total. Plus overheads, supervision, profit and tax shown separately. If those last three are not separated, the document cannot be compared with anything.
Approximate shares for a mid-range house on this coast. They vary with design, but they are enough to spot an unbalanced budget at a glance — a finishes line at 12% or a foundation line at 4% is telling you something before you read the detail.
Compare line by line, never by total. Confirm both include the same items with the same quantities — the cheaper one has usually omitted three. Compare unit prices rather than totals. Ask what happens if steel or cement moves during the works. Confirm who pays permits, testing and final cleaning. And treat a lump-sum quote as what it is: a number that cannot be verified, from someone who would rather it were not.
| Section | Share of construction cost | Note |
|---|---|---|
| Preliminaries and foundations | 12% – 18% | Higher where limestone complicates excavation |
| Structure and masonry | 25% – 32% | Concrete, steel, walls, slabs |
| Services: plumbing, electrical, AC | 14% – 18% | Includes cistern and pumping |
| Finishes | 22% – 30% | The section that varies most by level |
| Joinery, metalwork, glazing | 8% – 12% | Kitchen, closets, doors, windows |
| External works and cleaning | 4% – 8% | Paths, garden, handover |
Quantities given "as a lot" for work that is measured per square metre. Finishes described as "high quality" with no brand or model. Services with no gauge, diameter or capacity specified. Pool, landscaping or boundary wall mentioned in the description but absent from the totals. And the big one: a budget produced without an executive project, which is not a budget at all — nobody can quantify what has not been drawn.
Fixed price against a line-item budget puts the performance risk on the builder and gives you a number you can hold them to; it requires a complete design. Cost-plus only works if you are on site, supervising, and willing to absorb variation — which describes very few foreign owners. We work fixed-price by line item, and change orders are priced and signed before they are executed.
Related pages: The construction contract · Cost to build a house in Mexico · Versión en español · Managing a build from abroad
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