Are Slate Hooks Better Than Nails?

A nailed slate is held near its head by two nails driven onto a batten, which is a thin timber lath fixed across the roof. The row above then covers the nail heads, so from the ground you see only clean slate. A hooked slate is held at the tail instead, by a metal hook that catches the bottom edge and is fixed to the batten behind.

Which one is the traditional method?

Nailing is the long-standing method on slate. Hooks, sometimes called clips, are the alternative that holds the slate by its tail. The two work on different principles: a nail holds the slate from the top, and a hook holds it from the bottom, so the loads on the slate differ and so does the way each fails.

A third method suits single repairs, where the slate above cannot be lifted. Our answer on the slate tingle describes it. Each method has a place, and the skill is knowing which to use where. Roofs laid long ago were nailed, and a repair that respects the original method tends to age in step with the rest of the slope, which is worth remembering when someone suggests a quick fix with clips.

The slate producer Cupa advises against hooks on any slope under 25 degrees, and separately notes that BS 5534 gives 20 degrees as the floor for natural slate. Between the two figures lies a band from 20 to 25 degrees where slate may be used but hooks may not. In that band the slate is nailed.

What if my roof is only just over 25 degrees?

Then the data sheet for the specific product is the final word, because makers set their own limits and some are tighter than others. We check the sheet, measure the pitch of every slope, and if the reading sits near the line we fix by the safer method. See our answer on the minimum pitch for natural slate for how pitch is measured.

Exposure to wind can tip the decision too. A roof on a hill, or at the end of a terrace, gets more uplift than one in a sheltered street, and we allow for that in the choice, which is why two neighbouring roofs of the same pitch can be fixed in different ways.

A nail's weak point is time. Iron nails in a damp lap corrode, and once they snap the slate slides. Roofers call the result nail sickness, and we cover it in its own answer. The remedy on a new or re-slated roof is to use nails that do not corrode, and to fix each slate with two at the right point.

Do hooks avoid the problem?

They avoid the nail through the slate, though a hook is also a piece of metal sitting in a wet spot, so what it is made of matters. A hook shows at the tail, and some owners dislike the look of metal at every edge. On a listed building a visible fixing may be a consent question too, and the look of the edge can matter to the planning team. Copper nails are one answer to the rusting problem, and other metals suit different roofs.

Either way, a fixing can only be as sound as the batten behind it. Soft or rotten timber will not hold a nail or a hook for long, so we test the battens as we go, tapping and prodding them along the course, and replace any that have gone soft before a single slate is hung.

The survey asks its questions in order. What is the pitch of this slope? What does the slate maker say about the fixing for this slate at this pitch? What did the original roofer use, and is it still holding? Is the building listed, so that the appearance of the edge matters?

Will I be told which fixing goes on my roof?

Yes. It goes on the survey alongside the pitch, and you see the photos of your own slope. If a roof sits close to the pitch limit, we nail it. If a repair is only a slate or two, we match what is already there where we can. Our slate roofing page gives the full picture, and the written price comes only after this visit. Between a patch and a full re-slate, the survey gives you the facts to decide, and a photo of the slipped slates is a good way to begin.