Penthouse floor

A penthouse floor is the usable storey at the very top of a building. It can sit under a pitched roof, with ceilings following the slope, or it can be set back on a flat roof with generous terraces in front. Turkish practice uses one term, çatı katı, for both. The second version is what most people picture when they hear the word penthouse.

Why the top floor is special

The top floor usually gets the best views and the most daylight in the building. With nobody living above, it is quiet, and roof windows or terraces connect it directly to the outdoors. In residential projects it is often the most valuable unit and the one marketing material puts front and centre.

Design considerations

• No other floor is as exposed to the weather; without careful insulation and waterproofing it overheats in summer and loses heat in winter.
• Terrace waterproofing, falls and drain details directly affect the comfort of the flat below.
• The permitted area, height and setback of the top floor are set by Turkish zoning plans and plan notes, and they vary from one area to another.

In visualisation a penthouse is usually told through two images: an exterior view from the terrace across the city, and an interior frame that captures the view through the glazing. Sunset light shows off these units better than any other time of day.