Slate is repaired differently to tile, and most bad slate repairs come from treating it the same. This guide covers tingles, nail sickness, matching and when a slate roof is finished.
The problem with refixing a single slate
Slates are nailed near the head and covered by the two courses above, so once a roof is complete you cannot reach the nail position of a slate in the middle of the field without lifting everything above it.
The correct solution is a tingle, a narrow strip of lead or copper nailed into the batten below and folded up over the tail of the new slate to hold it. Fitted properly it is neat, almost invisible from the ground and lasts for decades.
Slates stuck back with mortar or mastic will fall again, usually within a couple of winters, and the adhesive stains the slate permanently. Foam sprayed under a slate roof to hold failing slates in place is worse still, because it makes future repair impossible and can affect a sale.
Zinc tingles are cheaper than lead or copper and corrode faster. On a roof you want to leave alone for 20 years, the fixing material matters.
Nail sickness: the real question
When slates begin slipping in numbers across a slope rather than in one place, the usual cause is corroded nails rather than broken slates. The slate itself may have another 50 years in it while the fixings have reached the end.
In the loft this shows as rust staining on the battens and slate heads that are no longer held. At that point continuing to tingle individual slates is a treadmill, and stripping the slope, re nailing the sound slates onto new battens and membrane is the economical answer.
Welsh, Spanish and reclaimed slates differ in colour, thickness and texture, and a patch in the wrong material is obvious for the life of the roof. Size matters too: slates come in a range of imperial sizes and the wrong one throws out the headlap.
Reclaimed slate is often the right choice on an older Oxfordshire property, provided each one is sounded for cracks before it goes up. We keep matching in mind because a repair that shows from the pavement is not a good repair.
Replacing a handful of slipped slates with tingles is typically £180 to £450 depending on access. A larger patch across a section of slope, or a slope re nailed and relaid with the existing slates, runs into four figures and depends heavily on scaffold and how many slates survive the strip.
Expect a loss rate when reusing old slates. A realistic quote allows for a proportion breaking and being replaced with matched material, and says so up front.
How do I know if my slate roof is nail sick?
Slates slipping in several unrelated places, rusty streaks on the battens in the loft and slates that lift easily by hand all point to fixings rather than the slate itself.
Can slates be reused when a roof is stripped?
Often a good proportion can, particularly on older Welsh slate. Each one is checked and sounded, and the shortfall is made up with matched slate.
Are tingles a permanent repair?
A lead or copper tingle fitted correctly is a long term repair, widely used on listed and heritage buildings. It is only a stopgap when the surrounding fixings are also failing.
Why is slate work more expensive than tile?
Slates are individually nailed, need cutting and holing to size, and are heavier and more fragile to handle. It is slower work requiring more skill.
Do you work on Cotswold stone slate as well?
Yes. Stone slate is a different craft again with graded courses and specific fixing methods, and we cover it in our Cotswold stone slate guide.
Slates slipping on your roof?
We will tell you whether it is a handful of fixings or the whole slope, and we will show you the loft evidence either way.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.