Rear Box Dormers - A Rear Box Dormer is the most common type of Loft Conversion. As the name suggests it involves building a simple box on the back of the roof. This Box Dormer creates a lot of usable space inside the Loft and is relatively straightforward to build. Typically the roof of the Dormer is flat and covered either in Felt, GRP or Rubber Sheet. The walls are normally timber framed and clad in either hanging tiles or slates, or sometimes lead or wood effect boards. If needed the side wall is extended up to form a Gable End and the pitched roof is extended across to meet it, as shown on the house on the left below.