Full Product Manual

ManualsBrandsGCP Applied Technologies ManualsBuilding materialsGrace Ice and Water Shield HT 36 in. x 75 ft. Roll Roofing Underlayment (225 sq. ft.)

Ice Dams

Grace Ice & Water Shield

roong underlayment should be used

in conjunction with roof designs that minimize ice dam forma-

tion. In cold climates, it is particularly important to provide

proper insulation and ventilation to reduce the size of ice dams

and to avoid interior condensation. Cathedral ceilings must

include ventilation between rafters to allow for air ow to a ridge

vent. Well ventilated cold roof designs are particularly impor-

tant 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

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 unsup-

ported 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

underlaymentin fair weather

when the air, roof deck, and membrane are at temperatures of

40°F (5°C) or higher. Apply roof covering material at tempera-

tures 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 pressure. 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

Use Grace Ice & Water Shield on all of these

critical areas

Confined

Rake Edge

Eave

Low Slope Area

Chimney

Skylight

Valley

Eave

Ridge

Hip

Dormer

Corners

Flanged Windows

Sill

Exterior

Doors

Sill Plate

Ledger Board

Deck Joists

Grace Ice & Water Shield

Grace Tri-Flex

Grace Vycor

Plus & Vycor

Pro

Grace Vycor Deck Protector