How to keep your build on time and on budget

It was supposed to be a six-month build. The money was set aside, the contractor had experience and the design was approved. A year and a half later, the house still was not finished, the money had run out at the plastering stage and nobody could say how much was left.

There was no great disaster. There were dozens of small decisions without planning, without a detailed budget and without anyone checking. Here you will see how engineering controls the time and cost of a build, from the budget to handover.

Budget: what it really costs

It all starts with a simple question: how much will it cost? And there are two ways to answer.

The first is the estimate per square metre. It serves for an initial decision, such as finding out whether the plot and the size of the house fit your pocket. As a reference, there is the CUB, the basic unit cost, published monthly by the construction industry unions. But the CUB is an average: it does not know your design, your finishes or your plot.

The second way is the detailed budget, and that is what controls a build. It starts from the designs: each service is measured (cubic metres of concrete, kilos of steel, square metres of masonry, plaster, flooring), and each quantity is multiplied by a cost breakdown that adds up material, labour and equipment. Reference databases such as SINAPI, from Caixa, help calibrate these values.

The result is a spreadsheet with hundreds of items, organized by stage: preliminary works, foundations, structure, masonry, roofing, installations and finishes. And always with a contingency reserve, because every build has some.

With a detailed budget, you stop asking "how much does the build cost" and start knowing how much each stage costs. And that changes everything when it comes to negotiating, buying and monitoring.

Planning and scheduling

With the cost of each stage defined, planning comes next. The question now is: in what order and in how much time?

The engineer divides the build into activities and defines the logical sequence between them. You do not plaster before running the pipes. You do not lay the floor before waterproofing. You do not pour the slab before checking the reinforcement. Some activities can run in parallel; others depend on one another. The sequence of activities that cannot slip without delaying the whole build is called the critical path, and that is where control has to be strictest.

From this comes the physical-financial schedule: for each month, it shows what should be executed and how much it will cost. Added up month by month, it forms an S-shaped curve, slow at the start, faster in the middle and slow again at the finishing stage.

This curve is the yardstick of the build. Every month, actual progress is compared with planned progress. If the actual line falls below, the build is behind, and you find out in time to correct it, not in the month it was due to be finished.

And the financial schedule becomes your cash flow: you know how much you need available each month, with no surprises.

Financing through Caixa

For those building with financing, the budget and the schedule stop being just good practice and become a requirement. In construction financing, such as that offered by Caixa, the bank analyses the design, the budget spreadsheet and the physical-financial schedule before approving the credit.

Then, the money is not released all at once. It is released in instalments as the build progresses. At each stage, a bank inspection checks the percentage executed, and only then is the next instalment paid.

That is why a badly made schedule holds up financing: if the work is carried out outside the planned order, the measurement does not close, and the instalment does not come through. BARRETO.eng prepares the technical documentation for the financing and monitors the build so that it proceeds in line with what was approved.

Lump-sum or administration?

One of the most important decisions in a build is how to hire whoever will carry it out, and there are two main models.

• Lump-sum contract: the builder receives a fixed amount to deliver the build, or a stage of it, according to the design and the specification report. The advantage is predictability. The caution is that the scope must be very well described, because anything not written down tends to become an extra.
• Construction administration: the owner pays the real cost of materials and labour, and the administrator receives a fee for the management. The advantage is transparency and the flexibility to adjust choices during the build. The caution is that the final cost depends on strict control of purchases, productivity and waste.

There is no model that is right for everyone. There is the right model for each build, each owner and the level of definition of the design. When the design is complete and coordinated, a lump-sum contract works better. When the owner wants to take part in the choices, administration usually makes more sense.

In construction administration, BARRETO.eng takes care of purchasing, hiring and coordinating the teams, and controlling costs and quality, with regular accountability.

Supervision and technical visits

Even with a good builder, there is a question every owner should ask: who checks the work for me while I am at my job?

That is the role of supervision. The supervising engineer represents the owner and verifies that what is being executed matches the design and the standards. Before each concrete pour, they check the formwork, the shoring and the reinforcement: the gauge, the spacing, the cover. During the pour, they monitor the receipt of the concrete and the casting of the test specimens that will prove its strength. They check plumb, level and square, the installations before the walls are closed and the waterproofing before the floor is laid.

In addition, supervision measures what has been executed so that payments can be released, records everything in reports with photos and points out problems in time to correct them. An error found in the reinforcement costs minutes. The same error found after the pour costs a lot.

And for those who do not need continuous monitoring, there is the technical visit: a one-off inspection, at a decisive moment of the build or in the face of a specific question, with an objective report of what was observed.

Audit and consulting

There are also two services for specific situations.

A construction audit is suited to when the build has already happened, or is under way, and a doubt arises: does what was paid match what was executed? Is the quality in line with the contract? The audit compares designs, contracts, measurements and payments with what actually exists on site, and points out the differences.

Development consulting comes before everything else, in the decision to invest. Is it worth buying that plot to build houses for sale? How many units fit under the legislation? How much does it cost to build, how long does it take and what is the risk? Consulting answers these questions with numbers, so that the investment is a technical decision and not a gamble.

Common mistakes

• Starting with only the estimate per square metre.
• Having no schedule, and discovering the delay at the end.
• Signing a lump-sum contract with a vague scope.
• Paying in advance for work not yet executed.
• Leaving the build with no one checking quality before each stage is closed.

Frequently asked questions

How do I produce a reliable construction budget?

From the designs: take off the quantities of each service and apply cost breakdowns (material, labour and equipment), organized by stage, with a contingency reserve.

What is a physical-financial schedule?

It is the plan showing, month by month, what will be executed and how much it will cost. The cumulative total forms the S-curve, used to compare planned and actual progress.

Lump-sum or administration: which is better?

It depends on the design and on the owner's profile. A lump-sum contract offers predictability if the scope is complete; administration offers transparency and flexibility, but demands strict control.

What does a construction supervising engineer do?

They represent the owner, check the work against the design and the standards, monitor concrete pours, measure services for payment and record everything in reports.

How are instalments released in construction financing?

Instalments are released as the build progresses, proven by inspections from the financial institution based on the approved schedule.

What is a construction audit?

It is the check, by an independent engineer, that what was contracted, paid for and actually executed correspond, including quality.

What is the difference between supervision and administration?

In supervision, the engineer checks work executed by another company; in administration, they also manage purchasing, teams and costs.

Who pays for the bank's inspection in financing?

The rules and fees are set by the financial institution in each contract.