The short answer: which papers and where they come from
Gas work in a flat or house can only be done by an empresa instal·ladora de gas habilitada, a gas installation company listed in the Catalan RASIC register. You do not move pipes or appliances or issue paperwork yourself, but it is on you to make sure every document is received and kept.
The good news: an ordinary domestic installation that does not need a project requires no responsible declaration to the Generalitat and is not entered in any register. The procedure page for gas installations says so explicitly. Your file looks like this: the installation certificate (certificat d'instal·lació) from the installer, with the user instructions; the pre-supply test and commissioning certificate from the distributor if you have piped gas; a start-up certificate for each appliance; and, every 5 years, the periodic inspection certificate.
When you need new paperwork
A new installation, always. Beyond that, the regulation (Real Decreto 919/2006, ITC-ICG 07) treats as a modification any change of pipe material or route longer than 1 metre, any increase in consumption and any replacement of appliances with ones of different technical characteristics. Moving a gas hob to the new kitchen of an Eixample flat is a modification. Swapping an old water heater for a more powerful condensing boiler in a Castelldefels house is one too.
Reopening is another case. If supply has been cut for more than a year after a contract ended, the installation is handled like a new one, with the distributor's checks.
If you replace a boiler with one of identical characteristics and leave the pipework alone, that is not a modification, but the new appliance's start-up is still documented with its own certificate.
What to prepare and who does what
The installer. Check the company's RASIC number. They design the route, carry out the work, run the tightness test and issue the installation certificate. Along with it they must give you instructions for safe use and maintenance, including a sketch of the pipe route, materials and valves.
You. Provide access, sign a supply contract with a gas retailer and keep the documents. If the installation is bigger than a domestic one and needs a project (typical for commercial premises), a technician signs the project and the owner files a responsible declaration online; according to the procedure page on the Generalitat website in 2026, the fee is 11.65 €.
Flues. As a rule, combustion products must be discharged at roof level. The exceptions are room-sealed or fan-assisted appliances up to 70 kW useful output and natural-draught water heaters up to 24.4 kW, which may vent straight to the façade or to a ventilation shaft. In Barcelona a façade outlet also has to fit municipal rules, so agree on the outlet position before work starts.
Step by step: from the works to gas on
One: the installer does the work and the tests and issues the installation certificate. Two: for a new installation, once the contract is signed, you or the retailer on your behalf ask the distributor for commissioning (posada en servei). For a modification, the installer notifies the supplier, who then asks the distributor to reconnect.
Three: the distributor's visit. Their technician checks the paperwork is complete and inspects the visible parts of the installation, the rooms with appliances and their flues, and the valves. If all is well, they seal the meter, check tightness, turn the gas on and issue the pre-supply test and commissioning certificate, with a copy for you. For a modification, the regulation passes the reconnection charge on to the end user.
Four: appliance start-up. Whoever starts up the boiler or water heater gives you a start-up certificate. With bottled butane there is no distributor: the installer runs the checks and issues the installation certificate, and you keep a copy.
The 5-year inspection
Piped gas is inspected every 5 years. The distributor gives you 3 months' notice, and you may choose any registered gas installer to do it. If you do not reply, the distributor carries it out on a date and time it tells you in advance. It is charged only through your gas bill; you never pay anyone in cash. A pass gets you an inspection certificate valid for 5 years.
If defects turn up, you get a deadline to fix them, and the company that repairs them sends the distributor a new certificate of compliance. Butane works in a similar way: every 5 years the owner books a periodic check (revisió periòdica) with a registered installer.
A boiler maintenance contract is not mandatory. Read the terms before signing anything offered over the phone or at your door.
Common mistakes
Letting in an «inspector» who turns up unannounced. Check with your distributor whether an inspection is scheduled, and never pay in cash.
Asking a handyman to move the gas pipe. Without a registered company's certificate, the distributor will not turn the gas back on after a modification.
Not telling the supplier about a modification. The regulation puts this on the installer; make sure they do it.
Forgetting about the cooker hood. Open-flued appliances may only go in a kitchen if measures stop the mechanical extraction from interfering with the flue. Raise it with the installer when you plan the kitchen.
Losing the certificates. You will be asked for them when you sell or at the next inspection.
Rules change, so check the current procedure page before work starts. If you would rather not deal with it yourself, BCN YARD handles the paperwork together with the renovation.