Australia Storm Book

After The Storm - 24

Roof Repairs: Flashing and Sealing

General

Good, well-applied flashing and sealing can help prevent moisture damage to a roof. Pay particular attention to penetration; for example, plumbing sewer vent pipes, skylights, fan exhaust covers, chimneys, and/or dormers. Anything that actually comes up through the roof is critical. Mentioned earlier in this series was the need for flashing in roof valleys and on roof edges. Thus, to preserve a roof, penetrations, valleys, and edges all need careful attention.

  • Roof Penetration -- Specific printed instructions are provided by the asphalt shingle manufacturer. Follow these instructions carefully.

  • Roof Edges -- When water runs down your roof, especially in a slow rain, it pauses a moment before pouring off. At the moment of pause, it runs back under the edge of the shingle, often reaching and wetting the edge of the sheathing. If this happens repeatedly over the years, the sheathing rots.

This may be prevented in a number of ways. The simplest method is to edge the roof deck (sheathing) with metal. Fit preformed metal drip edging snugly against the fascia (edge) board at the eaves (edge) of the roof. Nail it every 12 inches with roofing nails centered in the top surface. Do this on the edge before applying the number 15 felt underlayment. After applying the underlayment to the entire roof, install the metal drip edge to the roof rake edge (sloping, gable end edges).

  • Roof Valleys -- Again there are several methods of adequately waterproofing valleys. The important thing is to give them the special attention required. Some methods are:

    1. Use 28-ga. galvanized, corrosion-resistant metal, minimum. Extend the metal from the center line of the valley a minimum of eight inches each way from the center. Sections must be jointed to provide adequate waterlock.

    2. Woven or closed valleys may be constructed by centering 36-inch wide, no less than number 50, roofing felt (tar paper) in the valley over the basic number 15 felt (tar paper).

    3. If the valley is made of laced composition shingles, number 30 felt (tar paper) extending 10 inches from the center line each way is acceptable.

    4. Two layers of number 90 mineral-surfaced cap sheet cemented together with the bottom layer not less than 12 inches wide laid face down and the top layer of not less than 24 inches wide laid face up.

Only a water-tight roof is considered an adequate roof. Inspect the job carefully and seal any questionable places with roofing cement (asphalt). Moisture control problems are the biggest maintenance job we encounter; avoid future problems now.

 

 

 

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