broken slate tiles from tree falling on roof
broken slate tiles from tree falling on roof
Tree fell on this slate roof causing serious damage

Slate Roofing Repair

Slate Roof Repair

Many slate roofs are already 100+ years old. Some of these roofs will eventually have to be replaced but others can continue to protect the home if maintained properly. In most cases, and especially on historic roofs, it is best to repair instead of replace whenever possible. A periodic inspection is the best way to determine how well you're roof is holding up. CD Kaller can identify issues such as broken, cracked, missing or weakened slates and repair these small issues before they become problems.

In cases where there is more damage, such as to the roof decking, we remove the slate covering that section of the roof with damage, fix it and then if the slates we removed are in good shape we'll re-use them, otherwise they will need to be replaced.

It is sometimes pretty obvious when the roof can be repaired and when it needs to be replaced but in a lot of cases it's a little more difficult. The CD Kaller inspection report can provide the information needed and the guidelines below can help you make the decision.

CD Kaller is a slate roofing contractor with real appreciation for older and historic buildings and our slaters are specialists in preserving that character on your slate roof whether its a small slate repair, a complete slate roof replacement or a new installation. We can help with annual inspections and our highly skilled slaters can repair your slate roof so it retains its character and continues to protect your home for a very long time.

We are charter members of the Slate Roofing Contractors Association

"I must tell you how pleased I am by the work you did on my roof. The roof is, as you know, a most daunting challenge. Besides being the original roof on my genuine Victorian house (built in 1885), the roof is incredibly steep and almost inaccessible, it's divided into dozens of different sections, each one aesthetically pleasing but because of that, full of angles, strange corners, and decorative touches that make every slate hard to reach, hard to work on without disturbing its fellow slates, and hard to get a stable footing from which to work....
...I'm so grateful for the excellent work you did and the pleasantness of working with an honorable, dependable, responsible, competent, intelligent and pleasant contractor. I'm truly thrilled with the relationship we had and the results of your magnificant craftsmanship. - Dr Alvin Seltzer - see more

Slate Repair/Replacement Guidelines

The National Park Service created a checklist to assist in the repair/replace decision making process, and on how to inspect and maintain your slate roof.

  • Consider the age and condition of the roof versus its expected serviceable life given the type of slate employed.
  • Calculate the number of damaged and missing slates. Is the number less than about 20%? Is the roof generally in good condition? If so, the roof should be evaluated for repair rather than replacement. Also, keep in mind that the older a roof becomes, the more maintenance it will likely require.
  • Determine if there are active leaks and what their source may be. Do not assume the slates are leaking. Gutters, valleys and flashings are more likely candidates. "False leaks" can be caused by moisture condensation in the attic due to improper ventilation.
  • Check the roof rafters and sheathing for moisture stains. Poke an awl into the wood to determine if it is rotted. Remember that very old, delaminating slates will hold moisture and cause adjacent wood members to deteriorate even if there are no apparent leaks.
  • Are many slates sliding out of position? If so, it may be that ferrous metal fasteners were used and that these are corroding, while the slates are still in good condition. Salvage the slates and relay them on the roof. If the slates have worn around the nails holes, it may be necessary to punch new holes before relaying them.
  • Consider the condition of the roof's flashings. Because slate is so durable, metal flashings often wear out before the slate does. Examine the flashings carefully. Even the smallest pinhole can permit large quantities of water to enter the building. Is the deterioration of the slate uniform? Often this is not the case. It may be that only one slope needs replacement and the other slopes can be repaired. In this way, the cost of replacement can be spread over many years.
  • Press down hard on the slates with your hand. Sound slates will be unaffected by the pressure. Deteriorated slates will feel brittle and will crack. Tap on slates that have fallen out or been removed. A full, deep sound indicates a slate in good condition, while a dull thud suggests a slate in poor condition.
  • Are new slates readily available? Even if replacement is determined to be necessary, the existing roof may have to be repaired to allow time for documentation and the ordering of appropriate replacement slates.

If you have questions about your existing slate roof or are interested in installing a new one we hope you will contact CD Kaller Inc. And please see our article on Why you should choose CD Kaller.