When restoring a historic stone and timber building, the roof is far more than just a weather shield—it is the critical cap of a living, breathing structure. For decades, the construction industry has treated old buildings like modern concrete boxes, sealing them tight with synthetic foams and impermeable membranes. This approach consistently leads to trapped moisture, dampness, and the inevitable decay of structural timbers.
At ECS, our philosophy is simple: build a vapour-permeable eco-envelope. A healthy building must be allowed to breathe, managing moisture naturally while delivering modern thermal and acoustic comfort. Here is how we engineer the ultimate roofing system for restorations in Western Asturias and beyond.
The Finish: Natural Slate vs. Traditional Tiles
The exterior finish of a roof must balance regional aesthetics, extreme longevity, and structural reality. While historic restorations in the north demand natural slate (pizarra), it is important to understand how it compares to the alternatives.
The Gold Standard: Natural Slate Split directly from raw stone, high-quality Spanish slate boasts a generational lifespan often exceeding 125 years. It is incredibly heavy—often weighing up to 50 kg per square metre—which requires a robust, properly engineered timber or I-joist framing system. However, its dense nature means it absorbs almost zero water (under 0.4%), making it entirely frost-resistant. Crucially, its embodied energy is remarkably low compared to manufactured alternatives.
The Clay Tile Alternative Traditional fired clay or concrete tiles (tejas) are the dominant choice across Spain’s Mediterranean and southern regions. While they offer a beautiful, historically appropriate aesthetic for many properties and are generally lighter and less expensive than a premium slate installation, they come with distinct disadvantages in harsh northern climates:
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Moisture and Frost Damage: Clay is inherently porous. In the wet, freezing winters of the Asturian mountains, clay tiles absorb rainwater. When temperatures drop below freezing, this trapped water expands, leading to spalling, cracking, and the eventual failure of the tile.
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High Embodied Energy: Unlike slate, which is simply cut from the earth, clay and concrete tiles require massive amounts of energy to fire in kilns, drastically increasing their carbon footprint.
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Shorter Lifespan: Even high-quality clay tiles typically require replacement decades before a well-laid slate roof.
Battling the Elements: Heavy Rain and Wind Protection
In regions battered by Atlantic squalls, a roof must act as a fortress against driving rain and high winds.
Natural slate is exceptionally wind-resistant. Because of its weight and the traditional method of double-nailing or hooking each individual stone to the battens, a slate roof can withstand gale-force uplift far better than standard overlapping clay tiles, which are far more prone to lifting in severe storms.
Beneath the slate or tiles, our Steico wood fibre system provides the ultimate secondary defence. The Steico Integral sarking boards feature a precision tongue-and-groove profile. Once locked together over the rafters, they form an entirely windproof and highly water-resistant secondary deck. Even if extreme winds manage to drive rain under the roofing finish, the Steico layer sheds the water harmlessly down to the gutters, keeping the interior structure completely dry.
Standing Up to Fire: External Defences and Internal Safety
Protecting rural and historic properties from fire—particularly in areas vulnerable to summer wildfires—is a critical design factor.
Both natural slate and traditional clay tiles are non-combustible, holding Class A fire ratings. As the first line of defence, they will not ignite from flying embers, effectively shielding the vulnerable timber roof structure below from external fire threats.
However, the true difference in fire safety lies in the insulation core. When exposed to fire, synthetic plastics like EPS (Expanded Polystyrene) and XPS melt rapidly, raining toxic, flaming liquid plastic into the building and emitting lethal black smoke.
Steico wood fibre behaves entirely differently. In a fire, dense wood fibre chars on the outside—much like a thick oak log—creating a protective carbon layer that severely slows the spread of flames and heat transfer to the structural timbers. It does not melt, and it does not emit the highly toxic gases associated with burning petrochemical foams, providing crucial extra time for evacuation and preserving the structural integrity of the roof for as long as possible.
Preserving Heritage: Exposing and Rehabilitating Historic Timbers
A core goal of our restorations is keeping the original interior roof timbers fully exposed. Because our insulation system sits above the rafters, we can proudly showcase the building’s structural history inside the living space. However, achieving this is far from simple.
After a century or more of supporting heavy stone and slate, historic roof structures are rarely perfectly straight or structurally pristine. To create a flawless, weather-tight base for the rigid insulation boards above, the existing framework must be meticulously levelled from the top down. This often involves packing or sistering the tops of ancient, sagging rafters to create a perfectly flat exterior plane, all while preserving the undulating, rustic aesthetic visible from the room below.
Furthermore, where historic beams have suffered localised rot or insect damage, we do not simply rip them out. Instead, we carefully cut away the damaged areas and splice in replacement sections of timber. This structural rehabilitation is an incredibly time-consuming and labour-intensive phase of the project, but it is absolutely essential. It ensures the roof can safely carry the immense weight of a modern slate installation while honouring the authentic character of the original building.
The Insulation Core: Rejecting Plastic for Wood Fibre
The most critical failure point in modern roof restorations is the insulation layer. We exclusively utilise natural, vapour-permeable Steico wood fibre over synthetic EPS and XPS. This natural approach vastly outperforms plastics across three critical metrics:
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Vapour Permeability: Wood fibre absorbs and releases moisture safely, actively regulating indoor humidity without losing its insulating properties. It prevents the condensation that rots historic timbers.
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Decrement Delay (Thermal Mass): Lightweight plastic foams heat up quickly, transferring summer solar heat into the living space in just 3 to 4 hours. Dense wood fibre provides a decrement delay of 10 to 14 hours, keeping the interior cool during the day and releasing heat only as the night air cools.
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Acoustic Dampening: The high density of wood fibre absorbs the drumming of heavy Atlantic rain, a feature lightweight foams simply cannot replicate.
The ECS Roof System: Flex and Integral
To achieve a highly efficient, thermal-bridge-free roof capable of supporting heavy natural slate, we utilise a dual-layer Steico system.
1. Steico Flex (Between the Rafters) We start with Steico Flex—semi-rigid wood fibre batts friction-fitted directly between the structural roof rafters. It expands to grip the timber tightly, flexing with the building’s natural seasonal movement to permanently eliminate air gaps and cold draughts.
2. Steico Integral (Above the Rafters) The core of our heavy roofing system is Steico Integral. These high-density, rigid wood fibre sarking boards are installed continuously over the rehabilitated rafters, completely eliminating thermal bridging. For historic restorations, this offers two massive advantages:
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Exposed Timbers: As mentioned, because the bulk of the insulation sits above the roof structure, the restored historic timbers remain completely exposed inside the living space.
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Structural Support for Slate: The exceptional compressive strength of Steico Integral allows heavy counter-battens to be fixed directly through the insulation and into the rafters, creating the robust base required to carry the immense weight of a traditional slate roof.
By combining the fireproof, weather-beating strength of natural slate with the thermal mass and breathability of wood fibre, we create roofs that honour the heritage of the building whilst securing its future for the next century.