13 Mar

NY Ice Damming | New York Residential Roofing Service

March 13, 2014

Bay Shore Roof Repair

Ice Damming is the result of multiple conditions and factors happening after a snow event in New York. Shingle roofs are designed to work with pitch and overlap. Shingles and flashings are layered from bottom to top and the angle of the roof uses gravity to “shed” water down and off the roof surface. If the “shedding” of water is obstructed from moving down and off the field of the roof, water will pool and begin to “seep” thru the overlapped shingles and leaks to the interior of the structure will occur.

What are the typical conditions and factors for Ice Damming?

1. Snow accumulation on shingle roof surface.
2. Moderate pitch of roof surface 2”- 6” /on 12 (see how to determine pitch)
3. North facing portion of roof.
4. Small of no soffit overhang.
5. Gutters
6. Lack of proper venting.
7. Poor insulation of heated space.
8. Penetrations: i.e.: plumbing pipes, skylights, chimneys.
9. Outside temperatures well below freezing in night time hours.
10. Excessive heat loss from bathroom fan, pull down stair, high hat lighting.
11. Rain or warm-up temperatures following snow and days of freezing.

Some or all of these conditions can cause the creation of an Ice Dam and water seepage.

To explain the process, after a fresh snowfall in Suffolk County and Nassau County, the snow that is siting on your roof should melt off uniformly when temperature rise above freezing and from sun exposure. The snow should also freeze uniformly when temperatures drop below freezing and sun exposure is gone. The biggest factor that causes ice damming in New York is “irregular thaw” of snow on the roof from thermal loss coming from the interior heated portion of the structure. The snow is not uniformly melting even though the exterior temperatures are below freezing. Portions of the roof experiencing thermal loss will thaw snow and some portions will not. When thawed liquid begins to move downward with the pitch of the roof and reaches a portion of lower roof not experiencing heat loss (usually the gutter edge) it refreezes. If you have ever seen an icicle form, it grows longer and longer as liquid water runs over it and refreezes.

This same effect happens on the roof except this ice growth goes up as liquid id fed from thawing roofs above, it moves over the frozen lower sections and creates a continuous “speed bump” of ice that continues to grow higher and higher as it is fed water. This is how an Ice dam on a shingle roof is formed. It usually takes 24 – 48 hours from the time of the snowfall to form. Once formed any water from additional thaw or rain is now obscured at the high side of the ice dam and will begin to seep under the shingle assembly.

Although Ice damming most typically occurs at the gutters edges and valleys, New York Residential Roofing Company has seen it occur in almost any portion of the roof under the right conditions.

Preventing or protecting your home and roof from Ice damming conditions can be done. Please review our NY roof maintenance Ice Dam Protection procedures in the New York Residential Roofing menu.

Serving the Suffolk County, Syosset, Dix Hills, Long Island, & Commack, New York area!