Structure Inspection Section#4 Roof Framing Quiz#3

You should have finished Study Session 2 and Quick Quiz 2 before starting this Study Session. This Study Session covers the common conditions encountered with rafters, roof joists and ceiling joists.

The estimated completion time is one hour.

Objectives
At the end of this study session, you should be able to:

• List eight common problems with rafters, roof joists and ceiling joists.
• List three causes of sagging rafters or ridges.
• List five causes of rafter spread.

Explain why a ridge beam helps prevent rafter spread.

Rafters are less likely to spread when there is a ridge beam because the rafters hang on this structural member. With a simple ridge board, the rafters are not prevented from dropping at the ridge. A ridge beam, if properly installed, helps prevent the rafters from dropping or spreading.

Give five causes of rafter spread.

1. Ceiling joists running parallel to rafters 
2. Ceiling joists not well connected to rafters 
3. Ceiling joist splices not secure 
4. Rafters not well secured to the structure 
5. Ceiling joists removed to create cathedral ceilings.

Give three causes of sagging rafters.

1. Rafters overspanned or undersized 
2. Too many layers of roofing materials 
3. Excessive loads

Give two examples of how you might differentiate between a roof leak and a condensation problem in an attic.

1. Condensation tends to be more uniform and widespread than leakage. Condensation is uniform laterally across the roof. 
2. Leaks tend to run down sloped roof surfaces following gravity.

How might you tell the difference between sheathing sag and rafter sag from the exterior of the house?

Sagging rafters cause a dishing in the entire roof surface and/or a sag at the ridge. Sheathing sag is a repetitive pattern across the roof between rafters, trusses or roof joists.

Where rafters have been cut to accommodate a skylight, for example, the roof loads must be transferred to adjacent rafters. How is this done?

Headers and trimmers (doubling of rafters) strengthen the roof around openings for dormers, skylights, etc. This is similar to the headers and trimmers created in floor systems at stairwell openings.

Proper endbearing is required for rafters and ceiling joists. Generally speaking, the minimum recommended endbearing is __ inches. (Insert a number.)

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