Everyone compares slate roofs on the price of slate. On a Victorian St Helens house with two or three stacks, the slate is often not where the money goes.
Ask what a slate roof costs and you will be given a conversation about slate: Welsh against Spanish, natural against fibre cement, new against reclaimed. All of that is real and it matters.
But on the Victorian and Edwardian housing that makes up much of St Helens, the slate is frequently not the largest variable. The junctions are — the places where the roof meets something that is not roof — and they are also where almost every leak on a slate roof actually starts.
A modern estate house often has one chimney or none, a simple rectangular plan and two roof planes meeting at a ridge. A house built during St Helens' industrial expansion frequently has two or three stacks, a rear outrigger with its own valley, a bay roof at the front, and hips.
Every one of those is a junction. Every junction needs lead, and lead work is slow, skilled and priced by weight. Two houses with identical measured roof areas can differ substantially in price purely on how many places the roof stops and starts.
It is worth knowing, because "we'll flash the chimney" covers a range from a proper job to a smear of mastic. A stack passing through a pitched roof needs, at minimum:
That is one chimney. On a house with three, the lead work alone is a significant part of the job — and it is the part that determines whether the roof is dry in twenty years.
The second big junction, and common on properties with a rear outrigger. A valley carries the water from two roof planes, so it handles more volume than anything else on the roof and silts up with debris if it is not clear.
It can be formed in lead — traditional, long-lived and slow — or with a proprietary GRP or metal trough, which is quicker and cheaper and reads as a visible line. On a prominent elevation, and particularly inside a conservation area, that is a real decision rather than a technical detail.
Which still matters, obviously. The main choices:
| Cost | Laying speed | Appearance | Service life | |
|---|---|---|---|---|
| Natural slate, new | Highest | Slow | Best | Very long |
| Reclaimed slate | High | Slow | Best for matching | Unknown remainder |
| Fibre cement slate | Moderate | Faster | Fair | Shorter |
| Slate-effect tile | Lowest | Fastest | Poor close up | Moderate |
Within natural slate, the grading matters more than the country of origin. Producers declare performance under BS EN 12326-1 for water absorption, thermal cycling and sulphur dioxide resistance, and in each case 1 is the best grade — so W1 T1 S1 is the best specification available. Ask which slate is being quoted and ask for its declaration of performance; the roofer obtains it from the supplier.
Slate itself is extremely durable. What fails is the fixings — every nail on the roof went in at the same time and has sat in the same conditions since, so they corrode together. The symptom is slates slipping in unrelated places over several years with no storm to explain them, and once that is general there is no repair for it.
The practical consequence for St Helens property: if the slates themselves are sound, they may be worth stripping, sorting and relaying on new battens and underlay rather than replacing. That keeps the appearance unchanged, which inside a conservation area — where the council's Article 4(2) guidance expressly lists alterations to a roof or chimney — is worth more than the aesthetic alone.
A re-slate renews a thermal element and engages regulation 23 of the Building Regulations 2010: thermal performance must be improved where technically and economically feasible, to 0.16 W/(m²K) for a roof in an existing dwelling under Approved Document L Volume 1. Sign-off is via building control — the council's service or a Registered Building Control Approver — or self-certification under a competent person scheme.
We will tell you how many junctions your roof has, what each needs, and what that means for the figure.
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Because it is slow, skilled and material-heavy. Lead is priced by weight and comes in codes of increasing thickness; a chimney needs a front apron, side soakers and step flashings, and a back gutter, all cut and dressed to the brickwork. It cannot be rushed and it is where roofs leak when it is.
Sometimes, if it is sound, the right code and long enough. Often it is not — old lead is frequently undersized, has been patched with mastic, or has split from thermal movement. On a full re-roof, renewing it is generally the right call while the access is there.
A number denoting thickness — the higher the code, the thicker and heavier the lead. Different details call for different codes, and using too thin a lead in an exposed position is a false economy. Ask which codes a quotation is based on.
It is worth considering while the scaffold is up, because it removes a junction permanently and junctions are where roofs leak. But it changes the external appearance of the building, which in a St Helens conservation area matters — the council's Article 4(2) guidance expressly lists alterations to a roof or chimney.
Apex Roofing covers Cheshire and the surrounding area for complete roof replacement, new slate and tiled roofs and re-roofing.
Apex Roofing Cheshire · 105 Fence House, Fence Avenue, Macclesfield SK10 1LM
Tell us about the property and the roof in St Helens, and we will come back to you — usually the same day.
Prefer to talk? Call 07377 461095 · WhatsApp +44 7465 861265 · Email apexroofing14@gmail.com
