Why 70% of construction projects in Portugal go over budget

Study after study on the Portuguese construction sector points to the same pattern: the majority of residential and commercial projects finish over the original agreed budget. Sometimes by 10%. Often by 30%. In some cases, by more than double.

The question worth asking is not whether this happens. It is why it keeps happening, and whether it is actually avoidable.

The budget problem starts before the first wall goes up

Most construction budgets fail not because materials get more expensive or labour costs rise unexpectedly. They fail because the original budget was never real to begin with.

In Portugal, the most common pricing model in construction is the open estimate: a document that lists approximate costs per category, with the implicit understanding that the final number will be confirmed once work is underway. This model transfers all financial risk to the client. The contractor quotes low to win the project, then adjusts once the client is committed.

The client, by then, has few options. Stopping the project mid-construction costs more than continuing. So they pay.

Three structural reasons behind cost overruns

The first is scope definition. A budget without a fully defined technical scope is not a budget. It is a placeholder. When the client and contractor have not agreed on the exact specification of materials, finishes, installations and technical solutions before signing, every ambiguity becomes a variation order during execution, and every variation order costs money.

The second is planning sequence. In many Portuguese projects, work begins before all the technical decisions are made. Structural elements go up before mechanical and electrical routes are defined. Finishes are chosen mid-construction rather than before it. Each late decision forces rework, which extends the timeline and inflates cost.

The third is oversight. Without permanent technical supervision on site, deviations from the agreed plan accumulate silently. By the time they are visible to the client, correcting them is expensive. Often, they are not corrected at all, and the client accepts a result that does not match what was quoted.

What a fixed budget actually requires

A construction budget can only be fixed if the scope it is based on is fixed first. This means full technical specification before any proposal is issued, a defined material and finish schedule agreed by all parties, a construction sequence that accounts for all trades and their dependencies, and a supervision structure that catches deviations early enough to correct them without major cost impact.

None of this is complicated. It is simply not the standard model in Portugal, because the standard model does not require it. Clients who do not know to ask for it do not get it.

The cost of the cheaper quote

The lowest quote in a construction tender is almost never the cheapest option by the end of the project. It is the quote with the most undefined scope, the most assumptions built in, and the most room for variation orders once work begins.

A fixed budget, delivered by a contractor willing to commit to it contractually, typically costs more on paper at the start. It costs significantly less by the end. More importantly, it allows the client to make a real financial decision before committing capital, rather than discovering the true cost halfway through a build they cannot stop.

That is the difference between construction as a controlled investment and construction as an open liability.