The styles that resulted fall within several categories. In the mainstream of Georgian style were both Palladian architecture—and its whimsical alternatives, Gothic and Chinoiserie, which were the English-speaking world's equivalent of European Rococo. From the mid-1760s a range of Neoclassical modes were fashionable, associated with the British architects Robert Adam, James Gibbs, Sir William Chambers, James Wyatt, George Dance the Younger, Henry Holland and Sir John Soane. John Nash was one of the most prolific architects of the late Georgian era known as The Regency style, he was responsible for designing large areas of London. Greek Revival architecture was added to the repertory, beginning around 1750, but increasing in popularity after 1800. Leading exponents were William Wilkins and Robert Smirke. In Britain, brick or stone are almost invariably used; brick is often disguised with stucco. In America and other colonies wood remained very common, as its availability and cost-ratio with the other materials was more favourable. Raked roofs were mostly covered in earthenware tiles until Richard Pennant, 1st Baron Penrhyn led the development of the slate industry in Wales from the 1760s, which by the end of the century had become the usual material. Versions of revived Palladian architecture dominated English country house architecture. Houses were increasingly placed in grand landscaped settings, and large houses were generally made wide and relatively shallow, largely to look more impressive from a distance. The height was usually highest in the centre, and the Baroque emphasis on corner pavilions often found on the continent generally avoided. In grand houses, an entrance hall led to steps up to a "piano nobile" or mezzanine floor where the main reception rooms were. Typically the basement area or "rustic", with kitchens, offices and service areas, as well as male guests with muddy boots, came some way above ground, and was lit by windows that were high on the inside, but just above ground level outside. A single block was typical, with perhaps a small court for carriages at the front marked off by railings and a gate, but rarely a stone gatehouse, or side wings around the court. Windows in all types of buildings were large and regularly placed on a grid; this was partly to minimize window tax, which was in force throughout the period in the United Kingdom. Some windows were subsequently bricked-in. Their height increasingly varied between the floors, and they increasingly began below waist-height in the main rooms, making a small balcony desirable.