When a contractor says a project will take six to eight weeks, they're typically counting the time when their trade is on site. They're not counting the time between trades — when the plumber has finished and the electrician isn't available for another two weeks. They're not counting the permit wait. They're not counting the week when the floor tiles are delayed at the distributor.
This isn't deceptive; it's how tradespeople think about time. Their frame is their own schedule. Your frame is the calendar: the date when you want to be back in your kitchen, or the month you've arranged to have guests, or the school term you're trying to finish before.
The gap between trades
In a single-trade project — painting, say, or a boiler replacement — the calendar timing and the work timing are roughly the same. In a multi-trade project, they diverge considerably.
A standard bathroom renovation involves at least three trades in sequence: demolition and any structural work, plumbing rough-in, waterproofing and tiling, then fixture installation. Each trade has its own schedule. The availability of the first trade has no bearing on when the second will be free.
A realistic project timeline needs to account for these gaps explicitly. Not "plumbing: 3 days" but "plumbing rough-in: 3 days, then 5–7 working days before tiler is available." Across a full project, the gaps between trades often add more time than the work itself.
Permit timelines
In France, a declaration préalable de travaux for a project that falls below the permit threshold typically takes two months from submission to decision — sometimes longer if the municipality requests additional information. A permis de construire can take three months or more.
These waits sit outside the contractor timeline entirely. A contractor who quotes "8 weeks" for a project that requires a permit is either not aware that a permit is needed, or is giving you a timeline for the work phase only, with the permit phase assumed to have already happened.
Finding out at the contractor stage that your project needs a permit you haven't applied for typically adds several months to the total calendar. This is one of the things the initial consultation exists to identify.
Material lead times and what they do to a schedule
Some materials ship in days. Others have lead times measured in weeks or months — certain tile ranges, made-to-measure kitchen units, specific sanitary ware, custom joinery. If any of these are on the specification, they need to be ordered before work starts, not when they're needed on site.
The problem is that material selection often happens late in the process — after quotes are received, after decisions are made about cost — and by then, there's pressure to get started. A material that takes ten weeks to deliver is incompatible with a site that's ready to receive it in three weeks. Something has to change: either the start date moves, or the material changes, or the project pauses mid-construction while waiting.
None of these outcomes is catastrophic, but all of them are avoidable with earlier planning. The scope document stage is the right time to identify any long-lead items and build their delivery dates into the project schedule.
What a usable timeline looks like
A timeline that's actually useful for planning distinguishes between work phases, inter-trade gaps, and external waits. It gives calendar dates rather than durations. It identifies the critical path — the sequence of dependencies where a delay in one element delays everything that follows.
Most contractor quotes don't do this, and it's unreasonable to expect them to — it's not what contractors are in the business of producing. But if you're planning your life around a project completion date, it's worth building that timeline yourself from the elements the contractors have given you, adding the gaps you know about, and then applying a buffer for the ones you don't.