Understanding Pitched Roof Types

A pitched roof is a roof that slopes downwards in one or more directions from a central ridge. The slope helps water and snow drain off the roof easily. The question asks about a specific type of pitched roof where the rafters, which are the structural members supporting the roof covering, slope in one direction only.

Let's look at the options provided:

• lean to roof: A lean-to roof is a roof that has a single slope. It is typically attached to an existing wall or structure, with the rafters leaning against it. The rafters slope downwards away from the supporting wall, creating a single sloping surface. This fits the description of rafters sloping on one side only.
• collar roof: A collar roof is a type of pitched roof where a horizontal timber, called a collar beam, connects opposite rafters somewhere above the wall plate level but below the ridge. This type of roof usually has two sloping sides.
• scissors roof: A scissors roof truss is a type of truss where the bottom chords angle upwards to meet at a point below the ridge. This creates an open ceiling space resembling scissors blades. This design typically involves slopes on two sides.
• coupled roof: A coupled roof is a simple form of pitched roof consisting only of pairs of rafters meeting at the ridge and supported by the walls. There are no ties between the rafters at ceiling level, making it suitable for small spans. This roof type also involves slopes on two sides.

Based on the descriptions, the pitched roof consisting of rafters sloping on one side only matches the definition of a lean to roof.