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Competency: Draw roof plans

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Presentation on theme: "Competency: Draw roof plans"— Presentation transcript:

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

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