By necessity, the Old World originals had steep roofs clad in thatch and designed to shed rain and snow. Clay or mud was used to fill the walls between the timber framing members, creating the familiar "half-timbered" appearance. Prominent chimneys are evidence of the fireplaces used to heat the home and cook food. Additional rooms may have been added as resources allowed, leading to an irregular floor plan full of cozy nooks and niches. At the height of their popularity in America during the 1920s and 1930s, English Cottage house plans replaced the thatch with slate or cedar shake, though the roofs were no less steep. False half-timbering alluded to the original construction style. Casement windows with small panes separated by lead or wood muntins illuminated cozy irregularly-shaped rooms with whimsical nooks and niches on the first floor, while dormers typically provided light to the sloped-ceiling rooms on the second. Modern English Country Cottage house plans offer more carefully-planned and functional layouts without sacrificing one whit of storybook charm.