Roof systems come in many varieties. There are many common design defects and installation deficiencies with roofing systems. Some of the more common design defects and installation deficiencies are:
1. Design Defects
Ice damming-- A failure to design adequate ventilation in the attic of the roof system. Heat build up in the attic can cause the temperature of the roof cladding closest to the ridge (ie, the top ) of the roof to become elevated to a point where snow or ice melts. As the snow and ice melt, they roll down the roof as water and re-freeze as the temperature of the roof cladding materials closest to the eve (ie, the bottom) is below 32 degrees Fahrenheit. That freezing water tends to get up underneath the roofing materials or the siding and causes mold and damage to sheathing, framing and other building components.
Inadequate storm water flow- This allows storm water to flow off of the roof at a rate of speed and in a volume that can be handled by the roof system.
Failure to Detail Roof Flashings- Ice and water shield ("IWS") and various flashings is a necessary element of a proper functioning roof system. Design drawings often fail to detail the required flashings and IWS so that subcontractors know exactly what needs to be installed and the locations in which it needs to be installed. Common failures include lack of detailing of chimney and chimney cricket flashings, flashings for roof-wall interfaces, flashings around the perimeter of flat roofing systems, failure to detail tie-ins between different kinds of roofing systems that adjoin each other and failure to design proper drainage on flat and other roofing systems, among many others.
2. Construction Deficiencies
Contractors often may not read the manufacturer's installation specifications for the roof materials being installed. Deficiencies commonly seen include: lapping the felt paper underlayment backwards; failing to install--or failing to install sufficient quantities of-- IWS; failing to install battens or fabricating battens from non-conforming materials or in a manner at variance with manufacturer's installation specifications; missing flashings or failing to install flashings correctly; improper nailing or lapping of shingles; failing to properly seal pitch pockets through which HVAC , electrical or plumbing conduit/pipes were run or other penetrations through the roof; failing to properly detail the junction of one roof system to another or a roof system to a rake wall; and failing to install gutters of adequate size or in a manner consistent with the applicable building codes, among many others.