I get asked this more than almost anything by catamaran owners planning a French adventure: can I take her through the canals? The short answer is usually no, and the reason is a single number you cannot argue with. But the full answer is more interesting, because it depends entirely on which canals, which boat, and what you are trying to achieve.
The number that decides it: 5.05 metres
France standardised its waterways under the Freycinet gauge in 1879. The locks built to that gauge are 39 metres long and 5.2 metres wide, and a vessel built for them cannot exceed 38.5 metres in length, 5.05 metres in breadth, 1.8 metres in draught, and roughly 3.5 metres of air draught.
That 5.05 metre beam limit is what stops most catamarans dead. A typical 12 metre cruising cat carries a beam of around 6 metres or more, which simply will not enter a Freycinet lock. The famous example sailors trade is the 12 metre catamaran with a 5.95 metre beam hoping to run from Arles to Paris, who discovers the smaller locks the hard way. Prout, one of the few builders who designed around this, deliberately kept some models inside the 5.2 metre chamber, which tells you how unusual it is for a multihull to fit at all.
A monohull, by contrast, is narrow by nature. A 12 metre cruising yacht with a 3.8 to 4 metre beam slides into a Freycinet lock with room to spare. That is why the canals are, overwhelmingly, monohull country.
Where catamarans can and cannot go
It is not quite all or nothing. The big freight-gauge waterways are wider. The Rhone, the lower Seine, the Saone in places and parts of the Rhone from Lyon to the Mediterranean take commercial barges far bigger than any yacht, so a wide cat can navigate those sections. The problem is connecting them. To cross France you almost always have to drop onto a Freycinet-gauge link at some point, and that is where a 6 metre beam runs out of road.
So a catamaran might enjoy a stretch of the lower Rhone or a wide river, but the classic cross-France canal trip, Channel to Med via the small canals, is effectively closed to it. If a cross-country passage is the goal, read the cross France by canal from the Channel to the Med route first, then measure your boat against every section, not just the famous ones.
Beam is not the only obstacle
Even a narrow-enough monohull has to clear three more hurdles, and a catamaran that squeaks under the beam limit still faces them.
Air draught is the quiet killer. Many old canal bridges give around 3.5 metres of clearance, and the Canal du Midi's standard is roughly 3.7 metres with some bridges tighter. A sailing yacht has to unstep its mast and carry it on deck on a gantry, which adds length fore and aft and raises the centre of effort for wind. A catamaran's bridgedeck and cabin top can themselves be too tall before you even think about a mast. I go into the clearances in detail in the piece on air draught on the French canals, because it sinks more plans than beam does on the canals people assume are easy.
Draught matters too. The Freycinet limit is 1.8 metres but many canals silt and you want to keep under about 1.5 metres in practice. A shoal-draught monohull or a lifting-keel boat is ideal. Most cruising catamarans draw little, around a metre, so draught is the one canal limit they easily beat, which is cruelly ironic given the beam problem.
Length is rarely the issue for a yacht, since few private boats approach 38 metres, but the full Freycinet gauge canal dimensions are worth memorising so you can check any boat against any waterway in one glance.
The honest comparison
If you are choosing a boat with the French canals in mind, the monohull wins comfortably. It fits the locks, it unsteps a mast and carries it without drama, and the whole hire and ownership ecosystem is built around it. A monohull also handles a lock more predictably: it sits against one wall, takes a bow and stern line, and rises or falls on a single fender line. Two of you can work it.
A catamaran's advantages, the space, the stability, the shallow draught, the twin engines for manoeuvring, are real on the open coast and largely wasted on the canals. The extra beam that gives you that lovely saloon is the exact thing the lock will not accept. And the twin hulls that feel so secure at anchor make rafting and lock-side handling awkward in a narrow chamber.
There is one situation where a multihull earns its keep on inland water: a narrow trailerable cat or a purpose-built canal boat. But a normal cruising catamaran bought for blue-water comfort is the wrong tool for the towpath.
Handling a lock: why hull shape matters
Spend a day in a canal lock and the difference between the two hull types stops being theoretical. A monohull comes alongside the lock wall, you pass a bow and a stern line up to a bollard or around a fixed riser, and the boat rides up or down on those two points against fenders. One person on the helm, one on the lines, and you can work a chamber calmly. The single hull sits naturally against the wall and the fendering does its job.
A catamaran in a chamber, on the rare occasions one fits, is a different problem. The twin hulls do not sit cleanly against a vertical wall, so you fender one hull and fight the tendency to skew. In a downhill lock with the water falling fast and the chamber turbulent, that awkwardness becomes work. Add the bridgedeck overhang and you have a boat that simply was not shaped for a 5.2 metre stone box. None of this is fatal, but it is one more reason the canals reward the narrow boat. If you want to understand what you are signing up for, read how a French lock works before you commit, whatever your hull count.
Cost and licence are the same either way
People sometimes hope a catamaran sidesteps the canal admin. It does not. A private boat using the French waterways needs the VNF vignette regardless of hull type, and the skipper of a boat under 20 metres needs an ICC with the CEVNI endorsement whether they are on one hull or two. The full picture is in the French canals beginners guide, and it applies identically to a slim monohull and a wide cat. The vignette is priced by boat dimensions and time on the water, so a beamy catamaran does not even save money on the toll; if anything its size counts against it.
So there is no paperwork advantage to offset the physical disadvantage. The catamaran pays the same to use a network it largely cannot enter.
What most catamaran owners actually do
They take the coast. Rather than force a boat that does not fit through locks that will not take it, they sail round, and France gives them a superb route to do exactly that. The catamaran's strengths come alive on the south Brittany cruising guide anchorages and across the Med, where space and shoal draught let you nose into bays a deep monohull cannot reach. The catamaran cruising in France coastal picture is genuinely good; it is only the canals that say no.
If you have your heart set on the canals and own a wide cat, the realistic options are to hire a canal boat for that part of the trip and leave your own boat on the coast, or to plan the canals into a future boat that fits. Plenty of cruisers do the first: a fortnight on a hired cruiser through the Midi or Burgundy, then back to the cat for the sea. The hire versus own boat on the French canals decision is worth reading if that is your plan, because hiring sidesteps the licence, the vignette and every dimension headache in one move.
The bottom line
The French canals were dug for narrow barges in the nineteenth century, and the locks have not grown. A monohull was, in effect, designed for them by accident; a catamaran was not. Measure your beam against 5.05 metres before you measure anything else. If you clear it, welcome to one of the great slow journeys in Europe. If you do not, the coast is waiting, and your cat will love it more than a lock ever would.
