Slate roof quotes can look wildly different for what seems like the same job, and the gap is almost never explained by one contractor being greedy or another being cheap — it's usually a difference in specification you can't see until you read the detail.
Here's what actually moves the number, and what to look for when two quotes for the same roof land far apart.
Slate grade and origin
A thin, low-grade imported slate and a thick, well-graded Welsh or quality Spanish slate can differ substantially in price per square metre, and that difference compounds across an average roof.
Origin also affects consistency: a batch with variable thickness and colour needs more sorting on site, which adds labour even before a single slate is fixed.
Nail sickness and stripping
On a re-roof, whether the existing slates can be salvaged and reused changes the material cost significantly — reclaimed slate that's still sound is effectively free stone, just needing sorting and grading.
Stripping a roof affected by widespread nail sickness takes longer than stripping one where slates come away cleanly, because more come off broken and need careful handling to salvage what's usable.
Deck preparation and detailing
Battens, underlay and any timber repairs found once the old covering is off are rarely fully knowable until the roof is stripped, which is why a competent quote should flag this as a provisional sum rather than hide it.
Valleys, hips and abutments need leadwork detailing that takes real time to get right — cut corners here show up as leaks within a few winters, not immediately.
Access and scaffold
Scaffold cost is driven by height, roof complexity and how long it needs to stay up, and on a full re-roof it's often one of the largest single line items — it isn't optional and shouldn't be quietly reduced.
A steep pitch or restricted site access adds time for both erecting the scaffold and moving materials, which a fair quote reflects rather than absorbs by cutting corners elsewhere.
Reading a quote properly
A proper written quote itemises slate grade and quantity, batten and felt specification, leadwork by location, and scaffold separately, so you can compare like with like against another quote.
If a quote is a single lump sum with no breakdown, ask for the itemised version before comparing it against anyone else's — otherwise you're comparing a number, not a specification.
What a cheaper quote has usually substituted
The most common substitution is slate grade — a cheaper, thinner imported slate that will delaminate a decade or two sooner than a proper grade, quietly swapped in behind an identical-sounding line item.
The second most common is leadwork: cheaper flashing gauges or mortar fillets used in place of proper leadwork at valleys and abutments, which fail sooner and cost more to put right than they saved.
Common questions
Why do two slate roof quotes for the same house differ so much?+
Usually slate grade, whether battens and felt are being fully replaced, and how leadwork is detailed. Ask each contractor to itemise these separately rather than comparing bottom-line figures.
Is scaffold cost avoidable on a re-roof?+
No — safe access for a re-roof of any size needs proper scaffold, and a quote that seems cheap because it's skipped this is putting the roofers, and your property, at risk.
Should I ask for reclaimed slate to bring the cost down?+
It's worth asking whether your existing slate can be sorted and reused rather than buying entirely new stock, which can reduce material cost meaningfully if the slate is in good condition.
Request an itemised slate roofing quote
We break every quote down by slate grade, deck work, leadwork and access, so you can see exactly what you're paying for.