BT01, TP09, BT50, housing permits, housing starts: the guide to French construction indicators nobody explains to you

The construction sector has a reputation for being opaque, populated with technical acronyms and indices only pros master. That's a pity, because these indicators actually concern far more people than one would think: every buyer of work, every real-estate investor, every local authority, every company that rents or buys premises is directly exposed to their movements. Here are the five key indicators of French construction, three on costs, two on volume, explained simply and placed in context.

Why construction doesn't read like the other sectors

Construction is a long sector. Between the decision to build and the delivery of a building, 18 to 36 months typically elapse. Which means two things for any executive or decision-maker who cares:

• Leading indicators exist, and they are particularly reliable, because each stage of the process (permits, site, delivery) is counted and published by the administration.
• The cycles are lagged relative to the general economy. Construction anticipates or follows, depending on the segment, but it never reacts at the same time.

To read this sector, two dimensions must be separated:

• Costs, measured by the indices (BT01, TP09, BT50, and others more specialised).
• Volumes, measured by permits and housing starts.

A good construction dashboard must always cross these two dimensions. A cost index climbing while volumes collapse doesn't tell the same story as a stable cost index with rising volumes.

BT01: the king index of building costs

What it is

BT01 is the reference index of building costs in France, published monthly by INSEE. It measures the evolution of construction costs across all trades: materials, labour, energy, equipment, overheads.

It's the index found in most construction contracts, because it serves as the legal basis for price indexation. An 18-month construction contract with a BT01 indexation clause sees its final price adjusted according to the index's evolution between signature and delivery.

Why it matters

The BT01 doesn't just measure cost inflation, it officialises it. When BT01 rises 2% year-on-year, it's the entire chain of indexed contracts that moves. A public client, a private developer, a homeowner who commissions a build, all are concerned.

Note: BT01 increases don't reflect a single cause. It can be materials (steel, concrete, wood), energy (fuel, electricity, heating), labour (construction wages, contributions) or equipment. Following only the overall BT01 misses the internal trade-offs that have their own importance.

What to watch

• The monthly published level by INSEE (with a 2 to 3-month lag).
• The 6 to 12-month trend, which gives a better reading than the isolated figure.
• The breakdown by component: materials, labour, energy, available from INSEE and the FFB (French Building Federation).
• The specialised sub-indices (BT09 for masonry, BT38 for painting, BT50 for renovation), useful depending on the trade.

For a non-construction decision-maker: if you commission work on your premises, always check the indexation clause. A BT01-indexed contract in an upcycle can cost 4 to 6% more at delivery than the price stated at signature.

TP09: the pulse of public works

What it is

TP09 is an index specific to public works, focused on asphalt (bituminous road surfacing). Published monthly by INSEE, it closely tracks bitumen prices, a material directly indexed on oil.

TP09 is to public works what BT01 is to building: a contractual reference. It features in most public road contracts, roadway contracts and framework agreements between local authorities and public-works companies.

Why it matters

TP09 is one of the most volatile construction indices because it directly reflects oil prices. A durable drop in TP09 (like the one observed in 2025 at -8.6% year-on-year) translates into easing bitumen costs, hence renegotiation opportunities for public and private buyers.

Conversely, a surging TP09 signals stress on road budgets. Municipalities postpone work, public-works companies see margins melt, road-equipment suppliers feel the shockwave.

What to watch

• The link with oil prices: TP09 tracks Brent and diesel with a 1 to 2-month lag.
• The monthly INSEE publications.
• The related TP indices: TP01 (general public works), TP10 (concrete), TP02 (earthworks), which complement the reading.
• The budget choices of major local authorities and the State: when TP09 falls, deferred projects may restart within 3 to 6 months.

For a non-construction decision-maker: if your business depends on road quality (transport, logistics, local commerce), TP09 concerns you indirectly. A durably declining TP09 usually heralds a wave of roadworks within 6 to 12 months, meaning temporary disruption but also medium-term infrastructure improvement.

BT50: the renovation-maintenance index

What it is

BT50 is the reference index for maintenance and renovation work in buildings. It differs from BT01 in its composition: it gives more weight to skilled labour and small materials, and less to structural works and heavy equipment.

It's the index used for maintenance contracts, building upkeep framework agreements, and indexation clauses on renovation quotes.

Why it matters

The renovation market has become the main driver of French construction. New builds are shrinking under the effect of falling permits, while energy renovation takes over, driven by DPE obligations and public aids (MaPrimeRénov', CEE, éco-PTZ).

BT50 is therefore the index that's gaining relevance. A surging BT50 (because skilled labour is scarce, because artisans saturate their order books) signals lasting tension on the renovation sector.

What to watch

• The BT50 / BT01 spread: when it widens, tensions on renovation exceed those on new builds.
• Tensions on specific trades (electricians, plumbers, roofers), which have their own specialised indices.
• Public budget choices: MaPrimeRénov' reforms, CEE caps, DPE obligation changes, all influence renovation demand.

For a non-construction decision-maker: if you're a landlord or manage corporate real estate, BT50 is your compass. It drives the real cost of the improvement work you'll need to undertake in coming years, especially to bring your properties to energy standards.

Housing permits: the number-one leading signal

What it is

Housing permits correspond to building permits issued each month in France, consolidated by SDES (the statistical service attached to the Ministry of Ecological Transition). It's the very first indicator of the construction cycle: the official decision to build, long before work begins.

In 2025, France authorises on average about 20,944 housing units per month, a level in moderate rebound after several years of decline.

Why it matters

Housing permits are a powerful leading indicator, for three reasons:

• A permit filed today will translate into a start of work within 6 to 12 months, then a delivery in 18 to 36 months. The full cycle is traceable.
• Permit decisions reflect the anticipations of developers and households. A slowdown in permits says something about confidence in the market at 2-3 years.
• Permits move before cost indices. A permit collapse often precedes an easing of BT01 and BT50 indices via reduced demand.

What to watch

• The monthly SDES publications (available with a 2-month lag).
• The breakdown by type: single-family, multi-unit, specialised residences, each segment has its own cycle.
• The geographic breakdown: Île-de-France, major metropolises, rural territories, regional dynamics diverge strongly.
• Non-residential permits (offices, shops, logistics), which follow their own logic. The 13.8% drop in office permits in 2025, for example, is a major signal on post-remote-work restructuring.

For a non-construction decision-maker: if you sell equipment, furniture, moving services, insurance, home energy, you're exposed to the construction cycle with an 18 to 30-month lag. Reading permits today means anticipating your own demand in 2 years.

Housing starts: the cycle confirmation

What it is

Housing starts correspond to the effective start of work, published monthly by SDES. They follow permits with an average 6 to 12-month lag.

Why it matters

Housing starts confirm (or invalidate) the intentions materialised by permits. Between a granted permit and a start, many projects can be postponed or cancelled: rate hikes, developer failure, legal appeals, profitability changes, etc.

When housing starts decouple from permits, it's a sign that projects granted on paper aren't translating into action. It's often a more precocious warning than a fall in permits itself, because it reflects concrete distrust.

What to watch

• The housing starts / permits ratio: when it deteriorates, it's an unfavourable signal.
• The breakdown by type: a drop in multi-unit doesn't mean the same as a drop in single-family.
• The average lag between permit and start: a lengthening signals financing or sales difficulties.

For a non-construction decision-maker: this ratio is one of the most useful indicators to see where the cycle really stands. Permits can paint a flattering picture (developers keep filing projects), but if sites don't start, the machine is jammed.

How to read the 5 indicators together

The bulk of the value from a rigorous construction reading comes from crossing costs and volumes. Here are the four most frequent configurations to know.

A cost index climbing while volumes collapse doesn't tell the same story as a stable cost index with rising volumes.

The signals to watch in 2026

Several developments deserve particular attention.

• The BT01 / BT50 spread, which says a lot about renovation-versus-new-build tension.
• The TP09 trajectory in a context of reinforced carbon taxation and oil volatility.
• Office permits (in marked decline), materialising the post-remote-work restructuring.
• The housing starts / permits ratio as an early indicator of developer distrust.
• MaPrimeRénov' budget choices and renovation aids, which drive activity across the entire maintenance-improvement segment.
• ZAN (Zero Net Soil Sealing) rules that progressively constrain single-family permits and redraw the geography of new builds.

In summary

French construction isn't an opaque bloc reserved for insiders. It follows clear logic, driven by five key indicators: three cost indices (BT01, TP09, BT50) and two volume indicators (housing permits, housing starts). Reading them together allows any decision-maker to anticipate costs, lead times and sector cycles.

For an executive commissioning work, an investor preparing an acquisition, a public buyer planning contracts, or simply an economic actor exposed to construction dynamics, understanding these five indicators and their interactions is worth more than any approximate forecast of the sector.

That's exactly what Nexelys produces every month, cross-referencing costs and volumes and delivering 3, 6 and 12-month forecasts across the entire French construction cycle.