Box, mobile home or building: what an extra room really costs

To add a rentable room to a plot in 2026, three families of solutions exist. A new two-bedroom mobile home costs between €28,900 and €59,400, plus €2,500 to €6,500 for transport, levelling and utility connections, bringing the turnkey first-year budget to €40,000 or €55,000 according to 2026 trade sources. A fitted container-type module starts around €30,000. Building in masonry is the only option that durably adds property value, but it is also the slowest, the most expensive and the least reversible.

Purchase price is not the right decision criterion though. Here is why.

The mobile home: cheap to buy, restricted in use

2026 pricing is well documented. Budget €28,900 to €59,400 for a new two-bedroom model of 28 to 32 m². Add transport and placement at €1,000 to €3,000, levelling on pads at €500 to €1,500, and water, power and drainage connections at €1,000 to €2,000. Service life runs around twenty to thirty years with proper maintenance.

The real cost sits elsewhere. A mobile home may only be installed on a campsite, a leisure residential park or a classified holiday village. If your land falls outside those categories, the question is settled before budget even comes up. And for those renting a pitch, the annual fee commonly runs between €2,000 and €12,000 depending on the site, which changes the ten-year equation entirely.

One more overlooked point: beyond three metres wide, transport requires an abnormal load convoy. A placed mobile home rarely moves again.

Building in masonry: durable, slow, final

Costing new construction in an article would be meaningless, given the gap between regions, between a flat serviced plot and a sloping one with no utilities. What compares is the constraints: planning permission beyond twenty square metres, foundations, lead times counted in months rather than weeks, and a decision you do not undo. In exchange, the value stays on the balance sheet and operation can run thirty or fifty years.

For an operator wanting to test an activity before committing, it is the wrong tool. For one who has validated demand over several seasons, it is often the logical next step.

The placed module: the middle road

A fitted module, container or light frame, starts around €30,000 and rises with finish level. It sits on pads in half a day, with no foundations or heavy groundwork. It can be resold, it can be moved, it does not lock the land.

This is the format we chose at Hotel Inbox, with a design decision that weighs on running costs: 13 m² built as a room, not as a dwelling. No kitchen to equip or maintain, no living area to heat. A double bed, a shower room, serious insulation, and cleaning calibrated to fit in thirty minutes between stays. The Connected Box plugs into the site's utilities. The Off-Grid Box runs 48 hours for two adults with no connections at all, opening up plots the other two solutions rule out immediately. Our pricing is set on quote, according to configuration and unit count.

The criterion nobody weighs enough: reversibility

A masonry room that does not rent stays a building to maintain. A module that does not rent gets resold or moved. On a project whose demand is not yet proven, that difference is worth more than a few thousand euros of purchase price gap.

Ask the questions in this order: what does my land allow, how long do I want to commit, and what do I do if it does not work. Budget comes afterwards.