Flashing plays a key role in any roof repairs

Hey there, time traveller!
This article was published 12/05/2002 (8868 days ago), so information in it may no longer be current.

Question — I recently had the shingles replaced on my older Wolseley two-storey house. I was surprised to note that the roofers did not install any flashing. I’ve since noticed the same lack of flashing on two of my neighbour’s homes that have had new shingles installed.

I would have expected flashing to be installed around the edge of the gable window in the attic and also where the front porch joins the front wall of the house. I’ve seen roofing done on several of the home renovation television shows from the U. S. and it seems to be their standard practice to install metal flashing in these areas.

Is flashing necessary? I’m worried about ice forming in these areas and damaging the house. I had a small amount of water damage on the roof when I bought the house, which my home inspector advised was from an ice dam forming beside the attic gable window.

–L. Christianson, Winnipeg

Answer — The question in this letter I received last fall is now timely, as many people repair or replace their roofing after the snow is gone and the weather warms. Spring is the ideal time to inspect roofs for damage or deterioration that may lead to moisture damage of sheathing and other house components.

Missing or poorly installed flashing is a common problem found on older homes. As in the Christianson’s situation, many older homes have front and back porches built after initial construction of the home is complete.

The roof systems of these additions are often nailed directly on to the siding or wall covering of the main house, with little or no flashing installed. These areas are often prone to leakage and moisture damage due to rain and snow against the house. Ice damming may also be occurring if the addition is heated or the walls of the main house are poorly insulated. Escaping heat from the home will melt snow on the addition roof, and form ice at night as the temperature drops. This may be compounded if the roof is a low-slope shed style roof, as are many in this area of the city.

It may appear that the responsibility of adding flashings is with the roofer, but this is not normally done unless the homeowner specifically requests it. Roofers often quote on replacing only the deteriorated roofing, assuming that the original construction and flashing is adequate. A diligent roofer may include some flashing repairs in their quotation, but often just when a homeowner has pointed to a previous problem. Replacement of deteriorated or rotten roof boards may also be overlooked if the homeowner doesn’t request replacement of any damaged sheathing found after the old roofing is stripped.

To properly install flashing at the intersection of a roof and a wall it should be done before installation of the siding. The upper section of the flashing should be fastened to the wall sheathing behind the siding, with the lower section secured to the roof sheathing adjacent. The siding and roofing can then be installed and sealed at any openings with roofing cement. If this was the original method of installation, the flashing may actually be in place and not visible, after the roofing was redone.

This flashing method may be difficult or impossible to accomplish when replacing older roofing. Flashing installed after the fact may not be as effective, but still should be added, if possible. Sometimes, sections of siding may be removed and replaced after flashing installation. Another option is to install the flashing on the surface of the old siding. The lower section may be fastened either under or partially on top of the adjacent roofing. This is often more practical on retrofit situations such as the one faced by the Christianson home.

I have seen many good installations of this type that may incorporate a small piece of strapping at the top of the flashing, for proper securing. If the roofing is newly installed and the flashing is missing at the top of the roof, a row or two of shingles may be removed and easily replaced after flashing installation.

Too often, asphalt cement or caulking is used to substitute for a proper metal flashing at these intersections. This is a temporary solution, and will only be effective if resealed on a regular basis. Annual inspection and patching of these areas is critical to preventing leaks. Spring and fall are the best times to accomplish this, as the weather is warm enough to allow for proper repairs, but cool enough to make working in this tricky area more comfortable.

Ari Marantz is owner/inspector of Trained Eye Home Inspection Ltd. and is the P. R. Rep. for the Canadian Association of Home Inspectors- Manitoba (www.cahi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, P. O. Box 69021, #110-2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358.

trainedeye@iname.com