Nothing lasts forever, and neither will your roof. Whether you have slate, tin, or a flat roof, the weather and ultra-violet rays will eventually break down your roof system. It is important to have your roof inspected on a fairly regular basis. Here are a few tips concerning the different types of roofs with which we work.

Most roof systems suffer breakdowns owing to oxidation or ultra-violet rays. Oxidation occurs in all metals, to some degree. Many old slate and tile roofs were installed using steel nails that were not protected with zinc (galvanized) plating. Nails were made this way in the old days, in a very basic manner, and this is one of the problems facing many older slate roofs in the Richmond area.

As roofs age, and the nails oxidize, the gravity pulling the slates on the nails will eventually cause the nails to fail. As nails begin to fail, anything between 1 – 10 slates a year may become detached and fall from the roof. With 9,000 – 30,000 slates installed on a slate roof, it is not uncommon for some slates to fail annually. The only cure for this is to replace the slates and re-secure them to the roof deck. Although this is not necessarily a leak problem immediately, it will eventually require that the roof be removed and replaced with new nails.

The reason not every missing slate leaks is due to the roofing felt underneath. This felt, in good condition, will often drain the water to the eave of the roof for a short period of time; however, if the water hits a nail head or a split in the roofing felt on its way down to the eave, it will often leak. As the roof ages, the felt tends to deteriorate and this, obviously, will cause leakage at the first rain after the slate has slipped.

There comes a time with every roof when the annual cost of repairing becomes higher than the cost of borrowing the money to replace the roof. At some point, the owner should weigh out this decision on an individual basis. Of course, the inconvenience and insecurity of a leaky roof over an expensive property, as well as sheet-rock or plaster repairs and painting, has to be taken into consideration. We recommend roofs be inspected on an annual basis and that the appropriate repairs be made, as applicable.

Slate roofing

General
It is not unusual for a slate roof to last 80 – 100 years, if installed correctly. If a slate is cracked or holed, it is quite possible that the roofing felt underneath, if intact, would prevent water draining through the broken slate from entering the house. As the roof ages the felt begins to disintegrate and, as it disintegrates, the likelihood for a small leak entering through the slate roof and into the house increases. With an older roof (40 + years) it is more than likely that the water will end up as a nasty stain in the ceiling, which will need an expensive plaster and paint repair, not to mention any property that may get damaged inside the house as a result.

Flashing details
Most slate roofs have flashing details, which 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, etc. Normally, these are made out of either galvanized metal or copper. Both galvanized metal and copper, while good products, have their own particular problems.

Galvanized metal flashings, if not kept painted, will rust out over a period of time. It is essential to keep galvanized metal painted at all times to prevent this rusting; however, even with a good paint schedule, the flashings are likely to wear out after about 30 – 40 years. Some flashing (step-flashing) at the sides of dormers or around chimneys, etc., are installed underneath the slate; therefore, it is impossible to paint these. These tend to wear out a little sooner. Valley flashings – the section of metal connecting two different angles of roof – also are installed underneath the slate and these, again, cannot be painted. It is not unusual to have to replace various flashing details about every 20 years, even if well maintained.

Copper flashings have some advantages over galvanized metal, and the most significant of these is that they don’t need painting. Copper also looks very attractive when first installed, as it is bright and shiny. Be prepared, though, because within about 3 – 6 months this metal will turn to a mellower and also appealing brown color. Depending on the location, and the acidity, of the trees around your home it is possible that the copper will change from brown and begin to patina in as short a period of time as 5 – 8 years. Under certain circumstances, it is not unusual for the copper to take up to 15 years to start to patina. The patina is a result of the oxidation of the copper, and is the attractive teal green color that occurs over time. Although copper does not need painting, thereby making it maintenance free, it also wears 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 try to patch the holes in the metal, and this can be useful as a temporary patch; however, it is only temporary. If a flashing detail leaks at one point through a hole in the metal the next hole, and the next leak, is not long in coming. The only correct 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. This is all that was available many years ago, but now we use copper nails to secure slate to the roof. The great advantage, of course, is that the copper does not rust. After about 40 years, depending on the area of the slate roof, the old steel nails begin to rust and fail. It is not unusual at this point to see slates sliding off of the roof because the nails have rusted through. There is no solution to this problem, other than removing and replacing the slate roof with new nails.