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Grace technical support—Grace Ice & Water Shield

roong underlayment is backed by a team of local techni-

cal support personnel that help ensure every application goes

smoothly.

Guidelines for Use

Grace Ice & Water Shield

HT underlayment is a waterproong

underlayment designed for use on sloped roof decks and is suit-

able under most traditional roof coverings, including metal and

shingles for both commercial and residential applications. The

Grace Ice & Water Shield

HT membrane resists water penetra-

tion due to water back-up behind ice dams or wind driven rain.

It also offers leak protection in trouble prone spots like valleys,

skylights, protrusions and other ashing areas.

Ice Dams

Grace Ice & Water Shield

HT membrane should be used in

conjunction with designs which minimize ice dam formation. In

cold climates, it is particularly important to provide proper insu-

lation and ventilation to reduce the size of ice dams and to avoid

interior condensation. Cathedral ceilings must include ventila-

tion between rafters to allow for air ow to a ridge vent. Well

ventilated cold roof designs are particularly important in alpine

regions to reduce the size of ice dams which could contribute to

structural damage.

Several variables will inuence the height of ice dams and the

membrane coverage required.

1. Climate—The annual snow fall will affect the amount of

membrane needed.

2. Slope—On a low slope, ice dams will extend farther inward

from the roof edge.

3. Overhang—A wide overhang will require

more membrane to reach the appropriate point on the roof.

4. Insulation and ventilation—A very well

insulated building with a cold, well ventilated attic will have

smaller ice dams.

5. Valleys—Any valleys formed by projections such as dormers

or roof direction changes are likely to trap more snow and

cause larger ice dams.

6. Exposure—A northern exposure or shaded areas will generally

contribute to larger ice dams. While gutters may make it easier

for an ice dam to start, large dams can occur on roofs with no

gutters.

Removing snow from a roof edge or installing heat cables may

not prevent ice dam formation, but may shift the location of the

ice dam. Under certain conditions, a dam can form at the edge

of the remaining snow.

Local building codes should be consulted for specic require-

ments.

Installation Procedure

Surface Preparation

Install Grace Ice & Water Shield

HT roong underlayment

directly on a clean, dry, continuous structural deck. Some

suitable deck materials include plywood, wood composition,

wood plank, metal, concrete, or gypsum sheathing. Remove dust,

dirt, loose nails, and old roong materials. Protrusions from the

deck area must be removed. Decks shall have no voids, damaged,

or unsupported areas. Wood planks should be closely butted

together. Repair deck areas before installing the membrane.

Prime concrete, masonry surfaces and DensGlass Gold

with

Perm-A-Barrier

WB Primer. Prime wood composition and

gypsum sheathing with Perm-A-Barrier

WB Primer if adhe-

sion is found to be marginal (refer to Technical Letter 12, Use

on Oriented Strand Board (OSB) Roof Sheathing). Apply Perm-

A-Barrier

WB Primer at a rate of 250–350 ft

/gal (6–8 m

/L).

Priming is not required for other suitable surfaces provided that

they are clean and dry.

Membrane Installation

Apply Grace Ice & Water Shield

HT roong underlayment

in fair weather when the air, roof deck, and membrane are at

temperatures of 40°F (5°C) or higher. Apply roof covering mate-

rial at temperatures of 40°F (5°C) or higher.

Cut the membrane into 10–15 ft (3–5 m) lengths and reroll

loosely. Peel back 1–2 ft (300–600 mm) of release liner, align

the membrane, and continue to peel the release liner from the

membrane. Press the membrane in place with heavy hand pres-

sure. Side laps must be a minimum of 3.5 in. (90 mm) and end

laps a minimum of 6 in. (150 mm). For valley and ridge appli-

cation, peel the release liner, center the sheet over the valley or

ridge, drape, and press it in place. Work from the center of the

valley or ridge outward in each direction and start at the low

point and work up the roof.

Alternatively, starting with a full roll of membrane, unroll a

3–6 ft (1–2 m) piece of membrane leaving the release liner in

place. Align the membrane and roll in the intended direction

of membrane application. Carefully cut the release liner on

top of the roll in the cross direction being careful not to cut the

membrane. Peel back about

6 in. (150 mm) of the release liner in the opposite direction of

the intended membrane application exposing the black adhesive.

Hold the release liner with one hand and pull the roll along the

deck with the release liner, leaving the applied membrane behind.

Use the other hand to apply pressure on the top of the roll. Stop

frequently to press the membrane in place with heavy hand pres-

sure. When nished with the roll go back to the beginning, reroll

and pull the remaining release paper from the material, nishing

the installation.

For successive membrane courses, align the edge of the release

liner with the dashed line provided on the surface of the

membrane to achieve the 3.5 in. (90 mm) side lap.

Consistent with good roong practice, install the membrane such

that all laps shed water. Always work from the low point to the

high point of the roof. Apply the membrane in valleys before the

membrane is applied to the eaves. Following placement along

the eaves, continue application of the membrane up the roof. The

membrane may be installed either vertically or horizontally.

Use smooth shank, electro-plated galvanized nails for fastening

shingles to get the best seal. Hand nailing generally provides

a better seal than power-activated nailing. If nailing of the

membrane is necessary on steep slopes during hot or extreme

cold weather, backnail and cover the nails by overlapping with

the next sheet.

Extend the membrane on the roof deck above the highest

expected level of water back-up from ice dams and above the

highest expected level of snow and ice on the wall sheathing on

vertical side walls (dormers) and vertical front walls for ice dam

protection. Consider a double layer of membrane