Very few types of roofing materials can match the natural beauty and longevity of a natural slate roof. A natural slate roof can last more than a century, making it one of the most durable types of roof systems you can purchase and install on your home. In order to get the maximum life out of your slate roof, it must be regularly maintained and any issues must be quickly repaired. You will get the most service life out of your roof system if you inspect and repair it on a regular basis.
In order to complete an effective repair to your slate roof system, you must safely gain access to the area of the roof where the repair needs to be made. Slate roofs present safety obstacles that must be addressed in order to complete repairs safely.
The first thing to remember is that slate is a natural product. This means moss will grow on the surface of the slate. Slate will become slippery under inclement weather conditions, such as rain or snow. Take precautions by clearing any growth from the surface of the slate as well as removing snow or ice from the surface of the slates before attempting to walk on them. Always remember it's not safe to walk on the slate when it's wet.
The second thing to understand is that slate does not support foot traffic very well. It is best to avoid stepping directly on the slate when possible. This can best be accomplished by using a chicken ladder or other type of equipment that will support your weight while you make the repair. Risks associated with stepping on the slate include additional damage to the roof as well as slips and falls as a result of your feet slipping on the tile.
As you repair your slate roof, ensure that your access to the roof does not cause further damage to the roof system. Complete the repair in a way that minimizes your exposure to falls and injuries.
Before You Begin
Unlike most roofing materials, natural slate roofing is not commonly sold at big-box home improvement centers. You will likely need to consult a specialty roofing supply company to purchase slate roofing to match your existing roof, and these suppliers are more familiar with selling large quantities to professional contractors. Slate roofing tiles typically cost $10 to $15 per square foot, but you probably need to buy a bundle of tiles, which may well include more material than you'll need for the repair at hand. New tiles often are a poor match for weathered existing tiles, but you may be able to find exactly what you need at a retailer specializing in reclaimed tile products.
Equipment / Tools
- Flat pry bar
- Slate ripper
- Slate cutter
- Caulk gun
- Chicken ladder
- Tin snips
- Replacement slates
- Copper roofing nails deep enough to penetrate the decking at least 3/4-inch
- Sheet copper with 5-inch exposure on slate plus 2 inches
- Tubes of polyurethane caulk or asphalt mastic
Remove Damaged Slate Tile
When slate tiles are damaged, there are usually remnants of the tile left behind, including nails. These remnants must be removed.
Insert the top end of the slate ripping tool under the bottom edge of the slate tile or into the location where the tile is missing. You will notice that the slate ripper has a hook on either side of the top of the flat end of the ripper. The hooks are used to catch and cut the nails. As you catch the nail with the hooks, use your hammer to hit the handle of the slate ripper to drive the hook down against the nail. This will either cut the nail, or it will rip the nail out. Afterward, use the slate ripper to lift up on the slate and slide the slate out from its position.
Verify the Replacement Slate Tile Size
Once you have removed the damaged slate and nails from the repair area, lay the slate over the area to be repaired to confirm that the size of the new slate meets the dimensions required to complete the repair. It may be necessary to trim the slate to meet the dimensions needed. This can be accomplished by using a slate cutter.
If you can retain the slate that is being replaced, you may use the slate as a template for the replacement slate. Overlay the original slate onto the new slate and confirm that the size matches the slate being replaced. Trim the slate as necessary.
Install the Replacement Slate Tile
When installing the slate, it is important to remember that slates are not to be nailed tight. They are to be hung in place. In order to accomplish this, copper roofing nails should be driven to a point where they are flush with the surface of the slate while being careful not to overdrive the nails. If you overdrive the nails, you can crack the slate.
- Begin by sliding the slate into place. You do this by placing the slate tile under the slate directly above the location where the slate is to be installed. Slide the slate up and into place. You may feel some resistance; just apply pressure to slide the slate into place. If there appears to be too much resistance, it may be due to a small piece of the slate or a nail still in the way. Use the slate ripping tool to clear the area under the slates and remove any obstructions. Slide the slate to a point where the bottom of the slate is flush with the bottom of the slates on either side.
- Once positioned, you will attach the slate using copper roofing nails. Place the first nail between the two slates directly above the repair slate. The nail should be installed approximately 2 inches above the bottom of the slates. Begin by tapping the nail gently and then increasing pressure. If you attempt to drive the nail on the first hit, you will risk splitting or cracking the slate. The second nail should be installed approximately 2 inches above the first nail. Two nails are required in order to prevent the slate from rotating once in place.
Install the Copper Slip Under the Replacement Slate
After the slate is nailed in place, you will need to insert the copper slip.The copper slip is used to shingle the water over the nails and onto the exposed portion of the slate.
- Begin by cutting the copper slip so that it is approximately 4 to 5 inches wide. The length of the copper slip should be the full length of the exposed portion of the roofing slate plus an additional two inches in length in order to extend past the bottom of the slate.
- After measuring and cutting the copper slip, place a slight bend in the copper in the middle of the slip along the longest dimension. This bend in the copper slip helps to create tension and keep the slip in place after it is inserted.
- Slide the slip under the bottom edge of the two slates directly above the installed repair slate. It will extend from the bottom two courses above the repair slate and over the nails used to secure the repair slate. It may be necessary to use the hammer to gently tap the bottom of the slip to insert it fully.
When to Call a Professional
It cannot be overstressed that working on a roof comes with inherent dangers. With small repairs, a professional may be able to complete repair of slate rooting for less than $500. This can seem like a bargain if working at heights makes you uneasy. Large repairs are almost always better handled by pros.