Roofing refers to the materials places on the top of a building or structure to keep water (rain, snow and ice) from enter the building and damaging the interior of the building. Two common roof framing methods use trusses or rafters.  The most common roofing materials are shingles, tiles, shakes and metal panels.  Most roofing materials require underlayment which can be felt, paper, polypropylene, rubber, rubberized asphalt and synthetic.  When using shingles, there are two different strategies for nailing based on wind conditions.  Metal panels require either sheathing or purlins. 

Three panel shingles are relatively easy to use and available in most construction and DIY retailers (e.g., Home Depot and Lowe's).  Therefore shingles for a roof are the most commonly used roofing material.  Nonetheless, recent developments have lowered the cost of metal roofing and other materials. 

Roof Shapes

The most common shape of roofs are the basic gable roof (triangle ends), hip roofs (sloped on the ends), pyramid hip roofs (square up to a point), gambrel roofs (multiple slopes), and shed roof (single slopes).

Dormers are also a common item seen on a roof.  A dormer is departure from the normal roof structure to create more space (volume) and add a visual effect to the roof structure.