How to Build a Roof

Building an ordinary roof for a house, garage, or an extension is simple. Follow this procedure on how to add a roof to your building.

Materials Needed

These are the materials you will need.  The quantity of each item will depend upon the size of the roof you are building.

  • Wooden roof girts or beams (2X8 or 2X6)
  • Wooden roof rafters (2X4)
  • Roof purlins (2X3)
  • GI (galvanized iron) corrugated roofing sheets
  • Nails (1-inch, 2-inch, and 4-inch)
  • Umbrella nails
  • Roof ridge (plain GI gauge 24)
  • GI roof gutters
  • PVC downspouts
  • Anchor bolts
  • Ceiling rafters
  • Ceiling plywood panels


1. Place roof girts on the concrete or wooden posts of the house. Affix them there with embedded anchor bolts. Anchor bolts help on how to build roof girts that support the whole weight of the entire roof. Hence, roof girts should be 2 inches by 6 or 8 inches in thickness and width. This is a basic in simple roof construction. Roof girts often should come in two sets; one supporting the roof header and another the roof tail end.

2. On top of the girts, place the roof rafters. These rafters, with 2 inches thickness and 4 inches width, should be affixed to girts with machine bolt anchors. Rafters are always perpendicular to girts or beams, and parallel to the GI roof corrugation. To determine the number of rafters needed to support a roof, the space between two rafters should not exceed 1.5 or 2 meters. Hence, for a sturdy technique on how to build roof rafters, place 3 wood rafters for a roof 5 meters in width, for instance. Or 5 rafters for a width of 6 meters. This makes the simple roof construction dependable.

3. Place the wooden purlins on the rafters. Affix them by nailing with 4-inch nails. Purlins are always perpendicular to rafters and the GI roofing sheet corrugation. The space between purlins should always be .70 meters. Place them from the top of the roof to the gutter area. Purlins are necessary to ensure roof sheet permanence and how to build roof GI sheets into place.

4. On top of the purlins, arrange the GI roofing sheets, with a 6-inch overlap at the ends. Nail them on the purlins using umbrella nails. On the roof apex place the roof ridge. Affix it with umbrella nails. Install the gutters on each lower ends of the roof. Gutters should be secured by inserting the top part between a purlin and a part of the roof sheet. Affix with 2-inch nails. Remember, when building roof gutters, there should always be provisions for downspout drains and strainers.

5. Install the ceiling by affixing plywood panels on the ceiling rafters using 1-inch nails.

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