We certainly wouldn’t wish it on you, but the fact remains that many homeowners will find themselves living under a leaky roof this winter. When those wind-driven rains and snowstorms come rolling through, your daydreams of better weather might take the shape of a spring roofing project .
If your roof is prone to ice dams  and weather-related leak damage, before you lay down a new roof, think about laying down an ice and water shield first.
The ice and water shield membrane goes under shingles and seals around nails that hold the shingles in place, so water that doesn't drain properly cannot penetrate the roof and cause damaging leaks.
Ice and water shields are commonly used along the edges of a roof where ice dams tend to form. However, in parts of the country where severe weather is commonplace (like in the Hurricaine Belt), it’s not unusual to find that the entire roof was covered with a weatherproof underlayment beneath the shingles or other roofing material.
Keep in mind, though, that just because you have a roof leak, it doesn’t mean you necessarily need a whole new roof. Most types of roof leaks  can be fixed. Beware of contractors looking to make as much money as possible by selling you services you don’t immediately need.
If your roof is 15-25 years old, you’re most likely approaching the end of your roof’s natural life span anyway, and it might be a good time to consider roof replacement. Younger than that, however, and you’re better off addressing the source of your leak, unless your shingles are showing obvious signs of deterioration, like cracking or curling at the edges of asphalt shingles. Cracking could appear across the tab of the shingle, or the shadowline, which is the slot between the shingles.
Places where leaks most commonly occur are in spots where something is actually coming through the roof, like at the intersection of the roof and a chimney. Leaks also occur where two roofs come together (a “valley”). Or where pipes pass through the roof, such as above bathroom or kitchen ceilings . This is usually because a plumbing vent is located on the roof directly above the bathroom; the pipes are traveling from the bathroom straight through the roof where they vent.
In any event, ice and water shields provide added peace of mind for many years, even during the most brutal winters.