UK Timber Sizes
Understanding timber sizes in the UK can be confusing, especially when you discover that a 50 x 100 mm joist doesn’t actually measure 50 x 100 mm. The mix of nominal, finished, and planed dimensions, along with a few lingering imperial habits, can make ordering timber feel more complicated than it really is. Whether you’re a DIYer planning a deck, an architect specifying cladding, or a builder buying carcassing timber, knowing how timber sizes work helps you get the right material first time and avoid costly mistakes.