It is the most frequently declined line in a quote. It looks like spending on nothing: the design is done, the builder can read. Here is why it is not.

Waterproofing covered too early
On a house in Corbeanca, the foundation waterproofing had been laid incompletely at one corner. The visit caught it a day before backfilling. The fix: one hour of work. The cost of finding it two years later, through the basement: a few thousand euros and a rebuilt wall.

Displaced reinforcement
On a slab, the top reinforcement had been trodden down during pouring. It was visible in two minutes and was lifted back onto spacers. It would never have been visible after the pour.

A window 20 centimetres too low
An opening set out to the wrong level. Caught at masonry stage, redone in half a day. Caught after plaster and joinery, it would have stayed that way.

What you actually get
One visit a week, a written report with photographs after each, and the right to stop a stage that does not follow the design. That last point is the one that matters in the conversation with the builder.