FLASHING

Honey Joan L. delos Cientos -

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Scope of Work

All roofing sheets adjacent to the masonry walls and the top edge of the roof, shall be provided with Gauge No. 26 GI flashing (standard) with the same colour as the roof sheets.

Flashing 

It refers to thin continuous pieces of sheet metal or other

impervious material installed to prevent the passage of water

into a structure from an angle or joint. Flashing generally

operates on the principle that, for water to penetrate a joint, it

must work itself upward against the force of gravity or in the case

of wind-driven rain, it would have to follow a tortuous path

during which the driving force will be dissipated. Exterior

building materials can be configured with a non-continuous

profile to defeat water surface tension.

Flashing may be exposed or concealed

• Exposed flashing is usually of a sheet metal, such

as aluminium, copper, painted galvanized steel,

stainless steel, zinc alloy, terne metal, lead or lead-

coated copper. Metal flashing should be provided

with expansion joints on long runs to prevent

deformation of the metal sheets. The selected

metal should not stain or be stained by adjacent

materials or react chemically with them.

Drip Edge Flashing

Roof to Wall Flashing

Valley Flashing

Drip Edge Flashing

Proper practices for the installation

of roof drip edge flashing.

o Roofing drip edge or cap is the

metal flashing that covers the

wood decking at the edge of a roof

and supports the roof shingles.

o It is intended to prevent water

from contacting and damaging the

roof decking, prevent the roof

shingles from drooping over the

roof edge, and improve the

appearance of the roof line.

Drip edge installation.

bend drip edge to the roof pitch angle before installation.

• Unfortunately, most drip edge is bought pre-made from the factory. Meaning it comes in standard sizes with the downward flange fabricated at a 90 degree angle

Roof to Wall Flashing

flashing at roof to wall intersections should look like.

there will be a little more exposed metal along the rake walls, head walls, and chimneys but this "Z" Bar Flashing will look very nice if pre-painted. Besides, anyone can tell from 2 blocks away that you have a Veneer on your walls if you do not see metal. All real Brick or Stone through the roof walls and chimneys and those that set on lintels always have metal exposed at all intersections with the roof.

Valley Flashing

A) OPEN VALLEY

• The detail shows a typical open flashing for a shingle or slate roof. Two differentcants are illustrated. The cant strip can also be constructed as shown in Detail D. Theshingles or slate must lap the flashing at least 6 inches.

B) EQUAL SLOPES, UNEQUAL WATER FLOW

• Where unequal water flow is expected, a baffle, 1 1 /2 inches high, should be installedas shown to prevent water of higher velocity from forcing its way past the opposite edgeof the valley flashing. The baffle can also be constructed as shown in Detail D.

C) CLOSED VALLEY

• Intersecting roofs using a closed valley must have the same slopes so that the shinglebutts line up at the valley intersection. For roof pitches of 6" or more per foot theflashing extends at least 9" under the roof covering on each side. For roof pitchesless than 6 inches per foot the flashing extends at least 12 inches.

D) UNEQUAL SLOPES

• This condition requires a baffle for the same reason as Detail B. it canbe constructed as shown in either detail. This detail also shows a different cant strip.Other methods of raising the shingles away from the copper are shown in Details A and B.

ROOF SHINGLE FLASHING

• Figs A and B show method of flashing the break at a change of slope in shingle roofs. The flashing is formed with an inverted V and is hemmed top and bottom as shown. The apron portion of the flashing should cover a minimum of 4 in. of the top course of shingles. Top of flashing is nailed to the sheathing.

• Fig C shows a method of flashing the rake of a shingle roof. Flashing is formed in sections and is lapped in the direction of flow. Flashing is nailed to the sheathing 1 ft 6 in. on center.

Fig D shows a method of flashing the eave of a shingle roof. Flashing is formed in sections and lapped. Flashing is nailed to the sheathing 1 ft 6 in. on center.

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