Re-Use, or Skip? Natural Slate.

Why Natural Slate Still Matters on Heritage and Period Roofs

Around 90% of my work is heritage restoration. It is work I care deeply about and have built my career around.

Over the years, I have been fortunate to help restore some of Northern Ireland’s most important buildings, from churches and landmark structures such as St George’s Market in Belfast, to large period homes including the award-winning Ormiston House. These buildings matter. They carry history, craftsmanship, and responsibility. A roof on a heritage building is not just weather protection; it is part of the building’s identity.

I bring that same respect to period homes.

Many homeowners want to retain the character and story of their property while discreetly improving performance so the roof will last another hundred years. That balance — preservation combined with intelligent modern detailing — is where good roofing lives.

I have made no secret of my strong dislike for shiny fibre-cement “slates”. And I deliberately call them tiles, because they are not slate, no matter what the manufacturer calls them. When natural slate is removed from a period roof and replaced with fibre-cement products, something fundamental is lost.

Fibre-cement has a limited lifespan. The shine disappears quickly in our climate, the surface starts to break down, and the roof begins to look tired far sooner than it should. In fact, fibre-cement tiles I fitted as an apprentice could already be approaching the end of their service life today.

A natural slate roof, properly detailed and maintained, would not be.

A common reason for replacing a natural slate roof is nail fatigue — corrosion of the original fixings rather than failure of the slate itself. When a nail-fatigued slate roof is carefully stripped, a significant proportion of the slates are usually sound and suitable for re-use.

That raises a simple question:Why discard high-quality natural slate and replace it with an inferior product that is out of character with the building?

If you are receiving tenders for a re-roofing project and your existing roof is natural slate, you should ask for the following:

• An estimated percentage of slates that can be salvaged and reused. This will be an approximate figure, but it gives a useful guide. I typically aim for around 40% reuse.

• Confirmation that no sound, reusable slates will be removed from site.

• If you choose not to reuse them, ask for a rebate on the contract price, or sell the slates to a reputable salvage yard.

If you are reusing slate and need to make up a shortfall, reclaimed material can be sourced from specialist suppliers such as Architectural Salvage NI.

At the time of writing, the unit cost of a fibre-cement roof tile ranges from £1.60 to £2.04 ex VAT. If you already have around 40% of your roof slates available for reuse, you end up with a superior, more authentic material, a better-looking roof, and often a lower overall cost.

One of our recent projects used a mix of refixed original slates and carefully matched reclaimed Bangor Blue slates. The result was a roof that looked right, performed properly, and respected the building it sits on.

Heritage and period buildings deserve materials that age properly, perform properly, and belong there. That principle guides every roof I design and restore.

By Stuart Penrose, Founder of Stuart Penrose Roofing, heritage and period roofing specialist based in Northern Irelan

https://www.penroseroofingni.com/why-we-stand-out

Nail Fatigue