Heavy Snow on the Roof: When Weight Becomes Water

A lake-effect event can put a great deal of snow on a roof in a short time, and the risk arrives in two stages: the structural load while it sits, and the water when it melts. Call Buffalo Water Damage Restoration at (716) 261-2543 if water has come through a roof assembly.

Load does not sit evenly

Snow drifts on a roof the way it drifts on the ground. Wind moves it against parapets, into valleys, and behind rooftop equipment, so the load concentrates in specific areas rather than spreading across the structure.

Weight also changes with condition. Fresh dry snow is comparatively light; the same depth after a rain event or a partial melt and refreeze can weigh several times as much. The dangerous combination in this region is a large snowfall followed by rain, which the roof was never carrying when the snow first landed.

Low-slope roofs are the exposure

Buffalo's commercial and industrial stock is largely flat or low-slope, and those roofs shed nothing. Snow stays until it melts, drains have to carry the meltwater, and a drain that is frozen or blocked leaves the water standing on the membrane.

Ponded water finds the weak points in a membrane, particularly at seams and around penetrations. A roof that performs perfectly during summer rain leaks under a week of standing meltwater.

Interior drains freeze in this climate more often than people expect, since the drain line runs through unheated space near the roof deck.

The warning signs from inside

Doors that suddenly stick, new cracks in ceiling finishes, or a visible sag in a ceiling grid all indicate deflection, and deflection under snow load is a structural warning rather than a cosmetic one.

Creaking or popping from the structure is worth taking seriously. So is any water appearing at a column or along a beam line rather than at an obvious roof penetration.

In a house, a ridge line that has visibly changed shape, or interior doors on an upper floor binding in their frames, deserve immediate attention.

Removing snow without causing damage

Getting on a snow-loaded roof is genuinely hazardous and it is not the first move. Clearing drains and downspouts where they can be reached safely does more good than removing depth.

Where snow does need to come off, it comes off evenly. Removing all of it from one side of a structure while leaving the other loaded creates an unbalanced condition that can be worse than the original.

Shovels and picks damage membranes and shingles, and a torn membrane in February is a leak until spring. Roof rakes from the ground on residential eaves are the safe version; commercial work belongs to a contractor with fall protection.

What happens to the water inside

Roof water entering a commercial building typically arrives through the deck and then travels along it, appearing at ceiling tiles some distance from the entry point. Insulation above a suspended ceiling holds it, and the tiles themselves are a total loss where they were wet.

In a house it saturates attic insulation first and reaches the ceiling below afterward. Drying means removing wet insulation and treating the assembly rather than the stain.

Before next winter

Get the drains and scuppers cleared in fall, every year, and check them again mid-season. That single task prevents most low-slope water intrusion.

Have the membrane inspected while the weather is good, particularly at seams and around any equipment added since the roof went on.

Insurance and snow load

Damage caused by the weight of snow or ice is generally a covered peril on most policies, which puts it in a different category from the gradual seepage exclusions. Collapse, partial collapse, and resulting water damage are usually included.

Documentation should establish the load. Photographs of accumulated depth before removal, the dates of the storm, and any published snowfall totals for your location all support the claim, and removal costs are frequently recoverable.

Commercial policies often carry specific requirements about maintaining drains and removing snow, so reading those obligations before a storm rather than after is worthwhile.

Tenants and business interruption

Where the building is leased, water entering through the roof usually falls to the landlord's policy while tenant improvements and inventory fall to theirs. Business interruption coverage matters here because a roof repair in February can close a space for weeks.

Notify all parties the same day, and keep the scopes documented separately from the outset.

Serving Buffalo, Niagara Falls, Amherst and the surrounding region. Call (716) 261-2543.