Slate Roofing

If installed correctly, it is not unusual for a slate roof to last 80 – 100 years. If a slate is cracked or holed, the roofing felt underneath the slate could prevent water from entering the house. As the roof ages, however, the felt begins to disintegrate, and as it disintegrates, the likelihood of a small leak increases. With an older roof (40 + years) it is more than likely that the water will end up as ceiling stain, which is expensive to repair and repaint.

Flashing Details

Most slate roofs have flashing details. These are the pieces of metal used to join the slate roof to chimneys, make angle changes, or join a slate roof to a brick wall. Normally, these are made out of either galvanized metal or copper. Both galvanized metal and copper, while good products, have their own particular limitations.

Galvanized metal flashings, if not kept painted, will rust out over a period of time. Even with a good paint schedule, the flashings are likely to wear out after about 30 – 40 years. Some flashing, like step flashing and valley flashing, is installed underneath the slate and impossible to paint. They tend to wear out a little sooner. It is not unusual to have to replace various flashing details about every 20 years, even if well maintained.

Copper flashings don’t need painting, and that is an advantage. Copper also looks very attractive when first installed. Within 3 – 6 months, the metal turns an appealing brown color. Depending on the location and acidity of the trees around your home, the copper may begin to patina in 5 – 8 years. The patina is a result of the oxidation of the copper, and is the attractive teal green color that occurs over time. Under certain circumstances, it is not unusual for the copper to take up to 15 years to start to patina. Although copper does not need painting, it does wear out. With the increase of acid rain and, in some cases, minerals from the slate dropping consistently onto a flashing detail, the copper will begin to wear and holes will appear. The solution to this problem is to remove the flashing detail and replace it with new metal. Some people attempt a temporary solution by patching the holes in the metal, but the only permanent way to fix these details is to replace them.

We advise that a roof 40 – 60 years of age should be re-flashed if the slate is secure. This means that all flashing details should be removed from the roof and replaced with new metal.

Securing Slate
Most of the older slate roofs in our area were installed using steel nails. After about 40 years, depending on the area of the slate roof, the steel nails rust and fail, causing slate to slide or fall. The only solution is removing and replacing the slate roof with copper nails, which do not rust.

Saunders Roofing Company
1803 West Marshall Street Richmond, Virginia 23220
Call:(804)353-9919 E-Mail:psaundersr@aol.com