Slate Roof Repair & Maintenance

Slate roofs have been around for centuries in Europe, Spain, China, Africa and the USA. Composed of a fine-grain form of sedimentary rock such as clay or volcanic rock, when expertly “cut,” slates form smooth, flat sheets of stone that come in a variety of material colors, shades of gray, purple, green, blue and red. The structure must be designed to handle the weight of slate.

What to Consider Before Repairing a Slate Roof:

  • Before proceeding with any repairs, consider the age and condition of the roof versus its expected serviceable life and the type of slate on the roof.
  • The older the roof, the more maintenance is required. Where is the damage located? What is the percentage of broken or missing slates?
  • Determine if there is an active leak or if it’s just condensation — a “false leak” due to lack of ventilation. If it is an active leak, find the source.
  • Examine the attic for moisture – stains or dry rot. Delaminating old slates will hold moisture and deteriorate the wood members.
  • If slates have slid out of position, ferrous metal fasteners were used and have corroded. Slates can be salvaged and re-laid.
  • Metal flashings usually wear out before the slate. The smallest pin hole can permit water to enter the building. Check if the deterioration of the slate is uniform. If only one section needs replacement, the other areas can be repaired.
  • Test the condition of the slate to see if the pieces are sound. Tap on the slate. A full, deep sound means a slate is in good condition. Press down hard on the slates – sound slates will be unaffected.
  • New slates, when available, may take up to a year to get, depending upon size, shape and where they came from.


jpg45-68299_200x200Rusted Nail Head
If minor, remove slates with slate ripper. Install new slate with copper fasteners and a strip of copper.  If severe, salvage slates if possible from entire affected area and re-lay slates.


jpg47-85173_200x200Cracked/Broken Slate
Broken slates are usually a result of foot traffic or damage from trees or debris. If the slates are available and severely damaged, remove with a slate ripper and install new slates with new nails or a metal strip to hold the slate in place.


jpg46-100600_200x200Missing Slate
If the fasteners used to install the slate are severely deteriorated, it is time to take all the slate off and reinstall it. Typically, galvanized steel nails rot out before the slate is worn out. If copper nails were used, they will usually outlast the slates and it may be worth repairing. Evaluate the roof to determine if it is a repair or relay the slates. To repair, fasten new slate with a copper nail and/or a copper strip.


image_coming-26168_200x200Hip/Ridge Open
Adjust slates and/or install copper flashings under ridge tiles to divert water.


image_coming-26168_200x200Flashing Deteriorated
A temporary repair would be to apply the proper type of sealant to seal the flashing. A long term repair would be to remove the slate(s) and damaged flashing, install new copper flashing, and re-lay the slates.


image_coming-26168_200x200Deteriorated Slate
Verify the slate has deteriorated and determine the options and costs.


IMG_26101-79067_200x200Gutter in Stucco
When the house was built, the sheet metal installer put the gutter too close to the stucco paper. When the stucco was applied, it went around the gutter, not behind it. Over time the gutter joint can deteriorate, allowing seepage in the wall. Remove the gutter, cut the end back, reinstall the gutter end, repair the wall with waterproofing materials, then reinstall the gutter.


jpg85-89888_200x200Skylight/Flashing/No Overlap
The flashing does not go up high enough for the skylight frame to overlap the flashing and the wood curb is exposed. This is open and will allow seepage. Remove the skylight and install a counterflashing on top of the curb that overlaps the flashing on the side.


jpg14-77989_200x200Plastic Gutter
Plastic gutters do not come with a wing. The plastic gutter company makes a plastic diverter to divert the water into the gutter. If it is not installed, the edge of the roof deck will develop dry rot.


jpg37-149496_200x200Chimney Chase Leaks at Top
A chimney chase is usually a wood framed box.  The pipe for the fireplace goes through the box and out the top.  Typical roof chimney flashings are installed then siding covers the framing and overlaps the chimney flashing.  Last a metal top is installed which allows the chimney flue to go through to the outside air.  The metal top usually has a metal piece that prevents water from flowing down the opening in the metal top.  The flue usually has a collar that overlaps the metal piece on the metal top.  The flue usually has a metal top to prevent water from going down the inside of the flue.  Any one of these items in this assembly can leak if not done correctly or if it has deteriorated.  Invest all the potential issues and effect a repair.


jpg51-53016_200x200Broken Skylight
The amount of time it takes for the plastic dome to break down depends upon the quality of the plastic used to make the skylight. The dome can sometimes be replaced. It is easier just to replace the whole skylight. Some manufacturers give a lifetime warranty, even for plastic domes. Glass is heavier and more expensive than plastic. Glass has a higher R-value and lasts indefinitely.