Slate Roof Repair: The Don’ts
Slate roof repair experts will tell you that there are a few things that should never be done to a slate roof.
Do not replace a broken slate with mastic. Mastic is a plant resin used as a sealant. Although it will appear to be a good choice at first, the mastic will eventually harden and crack, allowing water to leak under your slate roofing. It will also make future slate roof repair more difficult, creates an unsightly mess and will corrode metal flashings.
There is a long-held belief that you can replace a slate with copper straps nailed underneath the slate, and hooked to the bottom. Do not do this -- they are aesthetically unpleasing, and not very functional as they will bend open if snow or ice slides down your slate roof.
Do not hire just any roofing contractor for the job. Those unfamiliar with slate roofing will not utilize the proper equipment, and may walk on your slate roof. You should never, ever walk on your slate roof. As well, there are many reports of inexperienced roofers nailing, tarring, caulking or even taping slates back into place.
Slate Roof Repair: The Do’s
Do inspect your slate roofing regularly. An inspection on the ground can alert you to the most obvious problems, like broken or missing slates. However, a closer inspection via ladder will show you smaller but still serious defects such as slate slippage, cracks or nail fatigue.
Do ensure your slate roofing contractor has the proper tools for the job. A ‘hook ladder’ is essential for a steep slate roof. Otherwise, scaffolding or a lift must be utilized. A ‘slate ripper’ is a specialized tool used to remove broken slates. It is a flat pry bar with two hooks on either side, which will pull (not cut) the nails out. A specialized ‘slate cutter’ will allow your roofer to size the new slates perfectly without damaging the integrity of the product.
Do ensure your slate roofing contractor has the proper know-how for the job. Ask them which method they will utilize for your slate roof repair job: slate hooks or the nail and bib method. Any other answer should send you packing (especially if they plan on nailing directly into the slates, and ‘securing’ them with tar.) Slate hooks are nailed into the roof sheathing, between the underlying slates. The replacement slate is slid in on top of it. The nail and bib method requires a single nail to be hammered into the replacement slate, in between the two slate tiles above it. Then a copper ‘bib’ is inserted underneath these tiles, but above the nail.
The bottom line is to take your time when contracting a professional to perform your slate roof repair. A poor repair job could mean a full roof replacement, which is not only expensive but a shame given the longevity of this beautiful form of roofing.