You’ve picked a freestanding bath you love off a screen, and a mate has told you the fan will ‘need to be a certain size’. It’s the sort of detail that only bites once the plasterer’s gone home. A recent plain-English guide to the 2026 bathroom rules lays it out: five Approved Documents under the Building Regulations and one British Standard cover nearly everything that matters in a domestic bathroom.
Some of it is numbers you can use straight away. Approved Document F wants extract of 15 litres a second on an intermittent fan, or 8 L/s on a continuous system. Approved Document G sets water efficiency at 125 litres per person per day for new dwellings and caps bath-fill temperature at 48°C. Unvented cylinders over 15 litres have extra rules too. Document M covers access, which matters if you’re thinking about a level-access shower or a wet room for a relative.
Then the electrics. BS 7671 divides the room into Zones 0, 1 and 2, and each zone has a minimum IP rating, so that lovely mirror light over the basin might be fine by the sink and wrong over the bath. Every bathroom circuit needs 30mA RCD protection, and under Part P most new circuits in a bathroom are notifiable. Brassware has to be WRAS-approved as well. It’s not red tape for its own sake. Water and mains voltage in a room that size need respecting.
This is why seeing the suites in person helps. Stand next to a wall-hung toilet, check the clearances, ask how far the shower tray sits from the door. And ask who’s installing, because a good fitter signs the job off against all of the above.
Grosvenor Merchants have a showroom in Aldershot on the A331 near the Ash Road junction, and their own team can survey, design and fit your bathroom, including adaptations for disabled access. Browse the range at http://grosvenormerchants.co.uk/ or call 01252 320 987 to arrange a visit.
