They are registered in England and Wales and they write about millimeters. I guess that they don't have 2x4 and 2x6 frames. Maybe houses there are built in a totally different way.
Yes, houses in England are not made from frames almost ever. They are made of solid brick. It was always so confusing to hear about Americans punching through walls. You can't do that here. There's no wood.
Yeah even interior walls here are mainly brick. Dry walls only exist in conversions where walls have been added that did not exist in the original construction. Even then, making thin walls like that is highly frowned upon and seen as a bit of a bodge job because the standard for the sturdiness of walls is high here.
