Can I Install an Ice & Water Shield After a Roof Was Put On?

Causes

• Ice dams form when snow and ice on a roof melt due to attic heat. Because the eaves of the roof have no attic heat, the ice and snow that accumulated there do not melt. This design causes a dam to occur. The water that has melted begins to seep down into the underlayment of the roof. It eventually makes its way down into the house. The ice and water shield is meant to protect the house, forcing the water to go elsewhere.

Location

• An ice and water shield will typically be installed in one of two primary places. In most cases, they are installed along the outer edge of a roof, which is close to where your gutters are found. This is the lowest area of the roof where water can collect if snow, ice or other debris prevents the water from running off. The other area is in the valleys between two roof sections that join each other to form a V shape. These valleys tend to be natural run-off areas for the water as well.

Preparation

• Ice and water shields prevent leaks by providing an impermeable membrane under the roof -- the membrane is meant to go beneath the roof flashing. Because these shields sit below the shingles and flashing, install the shield before putting in the roof, if possible. If you must install it afterward, you need to prepare your roof. To prepare for the shield, peel back some of your shingles and the flashing in the area that you intend to install it. Inspect the plywood underneath to determine if there were any leaks due to rotted wood or previously installed metal flashing. Clear out all of the shingles, flashing and tar paper in the area where the shield will go. Replace any rotted wood so that only fresh, bare plywood is showing.

Installation

• Once the roof has been stripped back to the bare underlayment, the water and ice guard can be installed by applying it directly to the wood. Many of these guards have adhesive backings that will form a permanent seal with the wood. Once this membrane has been laid down, replace the previous roofing materials by placing the flashing directly upon the water and ice guard. The shingles or metal roof is then placed back on top and secured in place.