Three Methods Of Preventing Icedams On Slate Tile Roofs
- Procedure code:
- Developed For Hspg (Nps - Sero)
- Thermal and Moisture Protection
- Slate Shingles
- Last Modified:
THREE METHODS OF PREVENTING ICEDAMS ON SLATE TILE ROOFS
A. This procedure describes three alternatives for
preventing icedams on slate tile roofs.
B. Ice-damming can occur on roof eaves when ice and snow
back up along gutters.
1. Ice can build up at the eaves from the intermittent
melting of snow. As the snow above melts and runs
down the roof, it eventually reaches the cold roof
eaves where it may refreeze creating a "dam" and
enabling additional snow to accumulate.
2. Accumulated water may then seep behind roof
shingles causing damaged to interior building
components such as insulation, plaster and framing
C. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
A. W.R. Grace & Co., Roofing Underlayment Options
Stormguard (shingle or metal); Weather Watch (shingle)
C. Snow Guards; Wikepedia "snow guards"
NOTE: Chemical products are sometimes sold under a common
name. This usually means that the substance is not as pure as
the same chemical sold under its chemical name. The grade of
purity of common name substances, however, is usually adequate
for stain removal work, and these products should be purchased
when available, as they tend to be less expensive. Common
names are indicated below by an asterisk (*).
A. For Metal Ice Edge:
1. Galvanized Steel: Available in 4 ft. x 8 ft.
sheets that permit a 3 ft. exposure of the metal
with a 1 ft. overlap of shingles. For more steeply
pitched roofs, less exposure is needed and 3 ft. x
8 ft. sheets should be adequate.
2. Metal primer and paint for exterior use
3. Mineral Spirits:
a. A petroleum distillate that is used especially
as a paint or varnish thinner.
b. Other chemical or common names include
Benzine* (not Benzene); Naphtha*; Petroleum
spirits*; Solvent naphtha*.
c. Potential Hazards: TOXIC AND FLAMMABLE.
d. Safety Precautions:
1) AVOID REPEATED OR PROLONGED SKIN CONTACT.
2) ALWAYS wear rubber gloves when handling
3) If any chemical is splashed onto the
skin, wash immediately with soap and
e. Available from construction specialties
distributor, hardware store, paint store, or
printer's supply distributor.
B. For Ice & Water Shield:
1. A waterproofing sheet made of flexible, rubberized
asphalt laminated to a polyethylene film.
2. Used as an underlayment along the edges of wood
shingle, slate, tile, cedar shake or metal roofs.
3.01 ERECTION, INSTALLATION, APPLICATION
A. Method 1 - Ensure There is Adequate Insulation and
Ventilation in the Attic.
B. Method 2 - Install a Metal Ice Edge: A metal edge
absorbs heat faster than shingles and, thus, tends to
shed ice from its slick surface during thaw.
NOTE: GALVANIZED STEEL IS PREFERRED OVER ALUMINUM. IT
IS NEARLY AS INEXPENSIVE, MORE DURABLE AND DOES NOT
EXPAND AND CONTRACT AS MUCH. HOWEVER, IT MUST BE
1. Paint the galvanized steel.
a. Wash the metal with a solvent such as paint
thinner or mineral spirits to remove any dirt
b. Etch it with a zinc primer and apply two coats
of exterior paint.
2. Firmly bed the metal in roofing cement and join in
sections with a crimped standing seam.
NOTE: It is preferable to cut the sheets in half,
providing seams every 4 feet, though it is possible
to join the full 8 foot length sections. HAVING
MORE JOINTS GIVES GREATER ALLOWANCE FOR EXPANSION
C. Method 3 - Install an Ice & Water Shield (in combination
with a snowguard):
NOTE: THE BEST TIME TO INSTALL THIS SYSTEM IS DURING A
1. Apply to a smooth and continuous sheathing.
2. The space under the membrane should be well vented,
as the shield acts as a vapor barrier.
3. If the shield is not installed during a reroofing
job, the lower 3 feet of the exposed roof will need
to be removed.
END OF SECTION