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Introduction

This section presents the most common roof and ceiling system problems and shows North American home builders how to avoid them. It does this by improving their understanding of design principles, material performance expectations and proper construction procedures.

Three main categories are presented:

These categories are discussed as they relate to structural deterioration and damage or to water leakage.

The roof constitutes the weather barrier for the attic and the remainder of the house, so it is important that it be durable. Recurring problems with such established roofing materials as asphalt shingles and wood shingles and shakes reflect the need for improved procedures. Tile and metal roofs, which are gaining in popularity, require extra care when they are designed, scheduled and installed.

Of course, good roofing structure is critical. Without a solid structure, sagging, shifting and water leakage are likely. Proper design and good workmanship provide a good base for the roofing materials, which in turn offer protection to the structural elements of the roof.

Problems with the interior ceiling finish, including sagging, wetting and the formation of mold, are also addressed. These problems can usually be traced to structural deficiencies or to problems with the roofing materials. Proper construction scheduling and control of the interior environment of the building during construction are also covered.

This section does not present all aspects of roof construction and some of the problems discussed here are more prevalent in certain parts of North America than in others, influenced either by regional construction techniques or local weather conditions. However, this section provides most of the information you will need to identify the causes of problems so that you may avoid creating imperfections during construction.

Area Primary Consideration Problem Cause

Roofing Materials

Structural Deterioration And Damage

Broken asphalt shingles.

Winds can lift shingle tabs, causing them to break.

Curled asphalt shingles

Water vapor penetration

Deterioration of asphalt shingle surface

Sunlight and high roof temperatures can cause differential hardening of the asphalt material through the shingle.

Shingle deformation and displacement

Improper or inadequate roof deck or improper fastening of shingles.

Rotting of wood roofing; rusting of metal roofing

Condensation on the underside of the roofing.

Cracked concrete or clay roof tiles

Damage by workers during construction.

Water Leakage

Flashing Failures

Inadequate size and improper installation of flashings.

Water penetration from ice damming

Inadequate eave protection

Water leakage through wood roofing

Excessive exposure length, no interlay between shake courses, and improper joint locations.

Water leakage of metal roofing

Thermal movement

Roof Structure

Structural Deterioration And Damage

Sagging Roof Sheathing

Inadequate support for the roof sheathing

Sheathing materials too thin to support concrete or clay tile roofing

Sagging roof support structure around openings

Inadequate framing around openings in roof trusses and rafters.

Roof structure sags around truss connections

Inadequate supports and poor fastening of connections,

Sheathing panels rise up at joints, causing ridging.

Roof panels installed too tightly

Water Leakage

Rotting of structural members and sheathing materials

Water leakage due to ice damming.

Excessive moisture in the attic space.

Water leakage around flashings

Interior Finish

Structural Deterioration And Damage

Wall-ceiling separation

Truss uplift

Wavy ceilings

High humidity and water absorption by ceiling drywall.

Excess humidity in the house during construction.

Wet ceilings due to attic condensation

Air leakage

Mold and mildew growth

Excessive humidity and cold spots.

Additional information on roofs and roofing