Key requirements for windows installed without the nailing flange:

FLASHING

When installing windows ‘without’ the Nailing Flange, Snohomish PUD requires Flashing along the top of each window that is not protected by a porch, soffit or an eave overhang extending at least 12-inches and that is within 25-inches above the window.

BACKER ROD OR NON-EXPANDING FOAM

Snohomish County PUD requires backer rod or non-expanding foam ONLY when there is a gap of 1/4″ or more between the rough opening and window frame. Anything under 1/4″ does not need it and would actually be difficult to install in such a narrow space.

NOTE: The standard for measuring and ordering windows is to shrink the current window size by nearly 1/8″ of an inch on all 4 sides. This means when measured correctly, there should never be a need for either backer rod or non-expanding foam.

Key requirements for windows installed with the nailing flange:

1) CAULKING

Snohomish PUD requires caulking to be installed between the nailing flange and the rough opening. An exterior quality caulk shall be used to seal the exterior trim to its contact point with the window frame and the exterior trim to siding to prevent water leakage.

2) WATERPROOFING AND SEALANTS

Snohomish PUD requires that all waterproofing materials be chemically compatible with the glazing seal. Glazing compounds sealants shall be installed with a slope to ensure water run-off.

WHAT TYPE OF CAULKING SHOULD BE USED?

Snohomish PUD requires that only an exterior quality caulk with a minimum 15 year product life is to be used in order to seal the exterior trim to its contact point with the window frame to prevent water leakage. The caulking shall also be paintable. The caulking that we use is one of the most popular brands amongst contractors & can be found at Home Depot, Lowes & Dunn Lumber. Here is a link to the caulking we use: – OSI QUAD CAULKING –