What Happens After a Snowmelt?
Winter snowfall can be brutal. Then comes the thaw, bringing snowmelt that can flood your basement or crawl space. Here’s what happens and how to prepare.
White, fluffy snow looks so beautiful early in the winter but can be a considerable threat to your home in the spring due to snowmelt and subsequent flooding. Refer to a spring maintenance checklist to make sure your home is in good condition after snowmelt.
To add some perspective, 13 inches of snow equals one inch of rain. Spread that out over a 2,800-square-foot roof and you have 1,743 gallons of water. That, of course, also depends on the nature of the snow. Wet, heavy snow might bring more than 5,000 gallons of water, while powdery, dry snow may only amount to 1,000 gallons.
Yet the real danger is the accumulation of snow on your home’s roof, on your lawn, and around your foundation. Week after week—and depending on where you live, perhaps month after month—of snowfall can build up. Plus, you’re moving all that snow off the driveway and sidewalks, piling it up further.
Rooftop Snow and Ice
As the snow on your roof builds up from snowfall after snowfall, there’s a tremendous amount of weight that adds up. Most roofs are specified to hold 20 pounds of snow per square foot.
Melting during the day and freezing at night can compact the snow, adding even more weight. Low-slope roofs are particularly at risk as the snow and water don’t run off as easily as a high slope roof.
Then there’s the problem of melting snow. Due to differences in attic insulation and exposure to sunlight, some parts of the roof may be warmer than others. This brings melting in the day and freezing at night with the water accumulating on the roof’s overhanging edge.
That can lead to an ice dam, which is indicated by those pretty icicles forming around the gutters. That, in turn, allows still more ice to accumulate on your roof since the water can’t move through the gutters and downspouts and builds up behind the ice dam.
Snowmelt Runoff
Worst case, the partially melted snow slides off the roof, completely bypassing the gutters. This leads to further snow accumulation around your foundation.
Yet another scenario is that the snowmelt water runs directly off the roof saturating the soil around the foundation—or it freezes, collecting as ice just waiting for the thaw that brings more water to your lawn and foundation.
Even when the snowmelt collects in the gutters and moves through the downspouts, it can find that the soil is still frozen or completely saturated from the snowmelt on the ground. Plus, there’s also the danger of an inadequately insulated basement or crawl space that warms the walls and melts the snow that has collected around the foundation.
All that water on the ground starts collecting, and without proper landscape grading away from the foundation, it starts flowing toward the foundation. Even with proper grading, once the soil is saturated, underground water flow toward the foundation can develop due to the clay bowl effect.
The clay bowl effect occurs due to soil excavation when constructing the foundation. The backfill soil has a different drainage factor than the surrounding undisturbed soil. This sets up a ready path for water to move toward the foundation.
What to Do About Snowmelt?
Prevention is the key to protecting your home from excess snow and ice accumulation and the resulting snowmelt.
- Attic and Foundation Insulation
Heat escaping from your roof or through the walls of your basement or crawl space can melt the snow and start water moving toward your foundation. Adding insulation can also save on heating costs.
- Remove Snow from the Roof
You can use a roof rake to clear excess snow, preventing the accumulation of snow, development of ice, and the excess flow of water during a thaw.
- Clear Snow from the Foundation
Clear the snow from around your home to a distance of four to six feet. This helps mitigate soil saturation around your foundation with warmer temperatures.
- Gutters and Downspouts
Make sure your gutters and downspouts are clear and ready to handle the flow of water. Downspout extensions and landscape grading should route the water away from your foundation.
- Fix Basement or Crawl Space Cracks
Water can find even small cracks, entering and then freezing, making them bigger cracks. So any cracks in your foundation should be identified and fixed so your home is protected during winter weather.
- Waterproof the Basement or Crawl Space
In addition to fixing cracks, installing an interior drainage system and sump pump in your basement or crawl space can remove water before it causes damage.
- Sump Pump System Maintenance
Make sure you take care of the maintenance of your sump pump drainage system. This includes making sure the drain lines don’t freeze in the winter preventing water drainage and potentially causing sump pump burnout.
For professional advice on protecting your home from winter weather and spring snowmelt, get a free inspection from your local basement waterproofing and foundation repair experts.