1. Competency: 205.00 Draw roof plans
Objective:
Apply concepts of roof construction.

2. Traditional Framed Roof (stick built)
Rafter size depends upon
The distance to be spanned
The spacing of the rafters (typically 24” O.C.)
The loads exerted on the roof from dead loads and live loads

3. Traditional Framed Roof (stick built)
Common rafters rest on the double top plate and extend to the ridge
Hip, valley, and jack rafters
Hip rafters extend from the ridge to a wall corner in a hip roof.
Valley rafters occur where two sloping roofs intersect forming a valley.
Jack rafters extend from the double top plate to either a hip or valley rafter.
Lengths vary as they occur higher on the roof
Shorter than common rafters

4. Traditional Framed Roof (stick built)
Collar beams
Typically placed ever 2nd or 3rd set of rafters
May serve as a ceiling joist for finished attics
Knee walls
Vertical studs that extend from the ceiling joists to the rafters.
Reduces rafter span
Adds rigidity
May form wall in finished attic

5. Roof Slope Rise Run Vertical distance
Measured from top of wall plate to underside of rafter
Run
Horizontal distance equal to half the clear building span

6. Roof Slope Span Roof pitch
Horizontal distance between load bearing walls
Roof pitch
Ratio of actual rise to actual span
Indicated by rise to run ratio
Run always expressed as 12

7. Cornice/Eave
Composed of all materials used to join roof to exterior sidewalls
Roof overhang
Protects walls and openings from weather
Controls natural light entering structure

8. Cornice/Eave Types Open Cornice Box Cornice Exposed beam construction
Rafter ends exposed
Sometimes tapered or curved for appearance
Box Cornice
Fascia
Forms eave line
Projects below soffit to form drip edge
Nailed to lookout

9. Cornice/Eave Types Box Cornice (cont’d) Soffit
Material that covers bottom side of rafter tail
Attached directly to bottom side of overhanging rafter
Bottom of rafter tail may be cut perpendicular to soffit
Nailing strip attached to sidewall serve as continuous nailing surface
Wide overhangs require lookout perpendicular to wall

10. Cornice/Eave Types Gable end (Rake)
Formed by extension of gable roof beyond end walls
Overhangs constructed similar to other walls
Lookouts attached to last rafters is less than 12”
Fascia attached to lookout

11. Roof Trusses
Prefabricated units include all members necessary to roof structure
Less expensive than conventional framing
Span long distances without interior load bearing walls or beams
Allows for open plans
Installed before interior wall construction

12. Roof Truss Assembly Top chord, bottom chord, and web members
Joined with plywood or sheet metal gussets for light construction
Available in many styles
Fink (W)
Howe (King post)
Scissors
Purlins (horizontal members)
Perpendicular to trusses provide stability & nailing surface

13. Roof Ventilation Cools attic area during summer
Removes moisture from attic
Bathing, cooking, cleaning
Condensation during winter

14. Roof Ventilation Prevents ice dams in winter conditions
Melting snow refreezes at colder edges of roof
Water behind ice dam soaks under shingles
Ventilation regulates attic temperature

15. Roof Ventilation Methods Gable end vents Cupola Louvered
Various shapes
Cupola
Small structure built above main roof level
Louvered sides allow air movement

16. Roof Ventilation Ridge vents Soffit vents
Projecting devices exhaust air from attic
Turbine vents have moving parts
Flat, non-mechanical vents allow airflow
Soffit vents
Allow air to enter attic
Continuous strips or individual units
Screen covers prevent insect and pest entrance