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Ice and Water Shield For Roofs: A Complete Guide

What exactly is an ice and water shield for a roof? Ice and water shield describes a roofing component specifically designed to protect vulnerable areas of roof decking from water damage.

The material is traditionally more popular (even required in some areas) in northern states where winters are longer and often more severe.

Source: gaf.com

Ice and water shield is usually sold in rolls with a self-adhesive backing, making it useful in protecting roof valleys, drip edges, and essentially anywhere additional protection is needed.

Why Would I Want an Ice and Water Shield?

Ice and water shield is technically an underlayment designed to be installed underneath a shingle, tile, or metal roof. Normally, this would be a felt underlayment commonly known as tar paper or roofing felt.

All underlayment products serve the same basic function, which is to prevent damage to the roof decking and extend the life of the roof. Underlayment provides an additional layer of protection should the shingles experience a perforation, such as from falling debris. The surface of underlayment also adheres very well to the adhesive strip found on shingles, ensuring a watertight bond. 

Ice and water shield takes the idea of underlayment a step further. Whereas standard underlayment is physically attached to the roof via staples or button cap nails, ice and water shield can be installed with no fasteners.

This greatly adds to the functionality and helps alleviate the possibility of water infiltration through an errant hole. Due to its self-adhesive design, ice and water shield tends to function as a gasket around fasteners as well to reduce leaks. This is especially useful if the roof has a low pitch, which causes ice and water to loiter and accumulate.

Are There Different Kinds of Ice and Water Shield?

Many manufacturers offer a version of ice and water shield, but generally speaking, they all serve the same basic purpose. Most ice and water shields will be rubberized, which not only makes the material water resistant but very pliable as well.

Some versions will be a simple sheet of rubber, while others may contain asphalt and other materials to increase their useful life.

Regardless, the function of most ice and water shield is to increase the moisture resistance of the roof decking in areas vulnerable to damage. Specifically, one main use of ice and water shield is to prevent damage caused by an ice dam, which is accumulated ice and snow that prevents proper drainage of water from the roof surface. 

How Do I Know If I Need an Ice and Water Shield?

In almost all situations, installing an ice and water shield is a very good idea. Ice and water shield is relatively inexpensive and provide insurance against potentially expensive roof repairs. In colder climates, ice and water shield is generally required by building code, but it is also very useful in warm climates.

In southern states that experience more rain than snow, ice and water shield protects the areas that receive the most water. These areas, such as valleys and the edges, can become worn long before the rest of the roof. Installing ice and water shield in these areas can extend the useful life of the roof by up to 50%.

Where Can I Use Ice and Water Shield?

In theory, the entire roof deck can be protected with ice and water shield. In most situations, it is used to protect the most vulnerable areas of shingle, mechanically attached tiles, and even standing seam metal roofs.

In practice, most professional roofing installers just install it in these vulnerable areas, or because the building code requires it. Ice and water shield is commonly used on low pitch roofs, and anywhere water tends to move slowly off of the roof.

Standing or slowly moving water is the enemy of roof decking, so any roof pitch lower than 3/12 should have ice and water shield installed, at least in the most vulnerable areas.

Can I Install Ice and Water Shield Myself?

It depends. Ice and water shield is usually self-adhesive, so messing around with tar and other sealants is not required. However, ice and water shield will look and function best when the material is perfectly flat and straight.

Because the material is self-adhesive, it sticks to itself and virtually everything else. This can cause a litany of problems for the installer unfamiliar with the process or materials. Unlike asphalt shingles, ice and water shield typically bonds directly to the roof decking upon contact.

An errant wrinkle or misalignment can be extremely difficult to correct, so in most cases, the project will require a helper. Needless to say, a do-it-yourselfer unconfident working on or near a roof is strongly discouraged from attempting ice and water shield installation.

Not only is the material tricky to work with, but installation generally requires working near the roof’s edge. Inexperienced installers have been known to accidentally step off the roof because in many cases they are facing the other direction during installation. Therefore, installing ice and water shield should only be attempted by those DIYers with the safety gear, experience, and tools to do the job successfully.

What Goes On First? Ice and Water Shield or Roofing Felt (Tar Paper) 

Most manufacturers of ice and water shield recommend that the material be installed first, directly onto the roof decking. This is due to the self-sealing feature of the material. 

For example, if roofing felt or any other non-adhesive underlayment is installed under the ice and water shield, the space between the tar paper and the roof deck is still vulnerable to water infiltration.

Conversely, if the ice and water shield is installed first, moisture penetrating the surface of the tar paper or roofing material will still encounter the ice and water shield. This is one major benefit of the rubberized material ice and water shield is constructed from.

As mentioned previously, ice and water shield tends to grip fasteners such as staples, roofing tacks, and button cap nails. As these fasteners are all very common to a roofing installation, the chances of accidentally creating a leak are greatly reduced when ice and water shield are installed underneath.

Most water damage to a roof can be traced to either faulty drainage or a perforation somewhere along the path the water takes towards the gutters. Even a single loose roofing tack can cause damage over time if the hole is not sealed. Since most of us don’t inspect our roofs as often as we should, installing an ice and water shield can be insurance against this eventuality.

Can I Use Drip Edge With Ice and Water Shield?

Yes. In fact, most manufacturers recommend using drip edge flashing as added protection for both the roof decking and the fascia board. To illustrate, roof decking generally extends beyond the edge of the rafters by approximately an inch to encourage rain or snow to fall straight into the gutter.

However, in practice, this protects neither the roof decking nor the fascia board to a large extent. Drip edge solves this problem by encasing both the lower edge of the decking and the upper edge of the fascia in metal, which is usually aluminum or galvanized steel. 

Since ice and water shield is self-adhesive, it will stick to almost anything it touches. This allows the material to adhere to wood, metal, or even itself. When ice and water shield is used in conjunction with drip edge, the bond created protects the structure from the top of the roof all the way to the gutter. This design, along with flashing, is considered to provide the most complete protection of a typical residential roof system. 

Where an ice and water shield is to be installed, it is important to install the tar paper, ice and water shield, and drip edge in the correct order. Since we’ve noted that the ice and water shield attaches directly to the roof decking, it will be installed first. Most professional roof installers will then install the tar paper over the ice and water shield, as this increases the total thickness of the underlayment.

Then the drip edge is installed over the tar paper. In theory, this method reduces the chances of a blowing rain making its way under the shingles. However, even if water is successful in getting in, the ice and water shield will prevent the water from seeping around nail holes or other perforations and contacting raw wood.

Ice and Water Shield Is a Great Investment

As we have discussed here, there is really no reason to not install an ice and water shield under a new roof if the budget allows for it. The material is relatively inexpensive, especially when compared to the costs incurred to repair wood damage and rot. Ice and water shield does its job very well and with careful, deliberate installation can add years to any roof.

2 Responses

  1. Thank you for this article on water proof underlayment! The inspector that looked at my new home was surprised to see the underlayment at the edge of the roof and caused me to worry that it may not have been installed correctly. After reading your article I can be confident that it was indeed installed as recommended, directly on the roofing boards, with tar paper and drip guard on top!

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