The Best Natural Building Materials for Eco Homes in the UK: Timber, Cork, Wool and More
We help landowners and homeowners extend their homes, build eco-homes, and create unique homestays that gain planning permission, perform well, and pay them back. RIBA Chartered Architects.
A section of one of our eco-home projects under construction. The curved timber frame uses a thin-profile reflective insulation chosen for the tight geometry, working alongside materials such as oak and cedar, which make up the cladding.
Why Natural Materials Matter
People looking to build on rural plots, farms and coastal sites want materials that age gracefully and reflect the essence of the surrounding context. Quality natural materials pick up and reflect their surroundings, ageing and often improving over time.
One of the things that has been quite pivotal to us as an architecture practice is that we operate a holiday home we designed and self-built, the Monocoque Cabin. I think this matters a great deal as we think about the longevity of the materials, how durable the materials are, and how long the materials last for. In my experience, natural materials have a far longer lifespan than synthetic materials.
There are also health arguments for natural materials, which have been substantiated by credible institutions, such as the World Health Organisation. Synthetic materials, common in new builds, some insulations, glues and composite products release chemicals into the home’s interior over time, a process known as off-gassing, which goes on for years.
In this article, we will look at five natural or low-impact materials we regularly specify, and why we use them. Our design philosophy and how we carefully select materials has been key to putting the list together.
1. Reclaimed Wood
Reclaimed wood is, without question, one of my favourite materials to work with. On a recent eco-home we completed, we used reclaimed scaffold boards internally for the flooring and reclaimed sapele hardwood for the external decking. What is great about reclaimed wood is that it has its own story; you may have seen merchants selling old maple floor boards from sports halls that still have the paint markings that divide the space, and scuffs to the floor layered over many years of contact. You cannot manufacture character.
If you're considering reclaimed timber, aim for hardwoods where possible: oak, maple, walnut, sapele. Softwoods can work in the right context; scaffold boards are typically softwood and can be used effectively internally, but hardwoods age the best.
Reclaimed timber offers three key advantages:
Character - Warmth, patina and authenticity that newer materials may struggle to replicate.
Proven durability - Reclaimed wood has already, therefore likely, been around for a long time. It will, therefore, likely survive for many more decades to come.
Cost - Reclaimed scaffold board flooring typically comes in at £15–22 per square metre of material against £53–92 for new engineered oak. Reclamation yards, salvage suppliers and even Facebook Marketplace are worth exploring before buying new.
The same logic applies to reclaimed brick or stone, particularly in localised context. Re-using stone and brick is an effective way of tying the thread of the structure with the context and surrounding landscape. It ties a new building into the history of its place, avoids the waste of manufacturing new materials, and brings a patina that new products cannot replicate. We are currently using reclaimed wood on our Renewable Container Livingproject; it remains one of the few materials that genuinely improves with age.
Reclaimed sapele hardwood decking on a recent project. Roughly half the cost of new hardwood, with character that new timber cannot offer.
2. Natural Fibre Insulation (Wool, Hemp, etc.)
Natural fibre insulation, particularly wool and hemp, is one of the most effective and most overlooked upgrades in an eco home. These materials are renewable, biodegradable and free from the petrochemicals found in many synthetic alternatives.
The reason it's so often overlooked is straightforward: insulation is typically specified at RIBA Stage 4, late in the design process, when the budget is already under pressure, and the default becomes the cheapest synthetic board that hits the U-value. PIR boards perform well thermally, but they are petrochemical-derived and non-breathable, and in a timber-frame building that is a condensation-risk decision, not just an environmental one. A breathable wall build-up manages moisture; a sealed one traps it. Most clients never realise the decision was made for them.
Two honest caveats, because they are the questions I get asked regularly. First, natural fibres need a thicker build-up: wool at a thermal conductivity of around 0.038 W/m·K needs roughly 170mm to match what PIR achieves at 100mm, so the additional space will need to be designed early in the process and cannot be post-rationalised around Stage 4 onwards. Second, cost: expect to pay 20–40% more than the synthetic equivalent. The following are the advantages you may expect:
Healthier indoor environments - No harmful VOCs. Wool, in particular, is excellent at regulating humidity, absorbing and releasing moisture without compromising its thermal performance.
Mould and mildew resistance - Particularly valuable for garden rooms, lofts, and holiday lets that sit unoccupied for weeks at a time.
Stable temperatures year-round - Natural fibres keep interiors cooler in summer and warmer in winter. With summer temperatures becoming so extreme recently, this matters a great deal.
When it comes to insulation, there is no “best insulation” per se, as the building’s fabric determines the choice of insulation. The choice of insulation is therefore a case-by-case situation.
3. Metal Roofing (Zinc and Standing Seam)
Metal is not a natural material in the traditional sense, but recycled metal roofing earns its place through sheer longevity. We use zinc regularly, including on the Monocoque Cabin, and it remains one of the most reliable and architecturally satisfying roof choices available.
Longevity — A well-detailed zinc roof lasts fifty years or more. Budget: £100–150 per square metre installed against £50–80 for concrete tiles: roughly double the cost, for double the lifespan or better, and none of the disruption of re-roofing a building.
Weather resistance — Essential on exposed rural, upland and coastal sites, where wind and rain break down softer roofing within years rather than decades. Natural slate is the traditional answer here and still an excellent one; it weathers beautifully and carries a sense of the place, but zinc achieves the same lifespan at lower weight, which opens up lighter structures and longer overhangs.
Passive cooling — Metal reflects solar heat, and paired with a well-designed overhang, it shades glazing through peak summer. As UK summers get less predictable, this is worth more than it used to be.
Aesthetic range — Against timber cladding, cedar shingles or dark-stained boarding, a metal roof reads as contemporary but grounded.
4.Cork
Cork has seen a massive increase in use in recent years. In my view, this can be attributed to a couple of reasons. Firstly, cork is harvested from the bark of a Quercus suber (Cork Oak), a tree typically grown in Portugal. The fact it’s taken from the bark makes it highly regenerative and sustainable to build with.
Secondly, if detailed correctly, cork can act as an insulating material, despite being an external cladding or internal lining.
Key benefits to cork include the following:
Real thermal performance - Cork has a thermal conductivity of around 0.038–0.040 W/m·K, which puts it in the same league as natural fibre insulation and makes it genuinely competitive as an external insulating layer or internal finish. As a result, when used alongside a natural internal insulation, it will reduce the amount of insulation needed.
Warm underfoot - Cork flooring is naturally soft and warm to the touch. A small detail, but one guests notice immediately, particularly in barefoot spaces like bathrooms and bedrooms.
Acoustic comfort - Cork absorbs sound, softening interiors that might otherwise feel hard or echoey. In open-plan spaces, this is the difference between a room that feels calm and one that feels like a canteen.
A finish that ages honestly - Cork develops character rather than deteriorating, which is the pattern with every material on this list worth specifying.
A current project at Markos Design Workshop is a timber-framed outbuilding using cork as the primary external insulation layer on the facade.
5. Natural Stone
Stone is the oldest answer on this list and still one of the best. It is the material that ties a building to its region more directly than any other — local stone literally is the landscape the building sits in — and in performance terms it does something none of the lighter materials can: thermal mass.
Thermal mass — Thick stone absorbs heat slowly and releases it slowly, flattening the temperature swings that lightweight buildings suffer. Cooler in a heatwave, warmer overnight in winter, with no mechanical help. Paired with a well-insulated envelope, mass is what makes a building feel calm and settled rather than reactive.
Sense of place — Stone sourced from the region picks up the tones and textures of its surroundings, which is why planners in sensitive landscapes respond to it. In National Landscapes and conservation settings, the right stone is frequently the difference between a scheme that reads as belonging and one that reads as imposed — and that is a planning argument, not just an aesthetic one.
Cost, honestly — full load-bearing masonry is the expensive route: budget £200–300 per square metre of finished wall and the structural implications that come with it. Stone cladding and plinth work deliver most of the visual and weathering benefit at £60–120 per square metre, which is where we typically deploy it — grounding a timber building into its site rather than building the whole envelope from it.
Endurance — Stone does not weather so much as improve. On exposed upland and rural sites it will outlast every other material on this list, and the maintenance schedule is effectively zero.
Traditional Techniques, Modern Performance
Timber framing has been central to British construction for centuries, and projects like our Black Barn show how that craft adapts to modern standards — airtight detailing, contemporary energy performance, heritage character. Old methods, applied with care, remain among the most robust ways to build.
None of this is new. Re-using stone has been critical to traditional British construction for centuries. The Ridge, one of our projects, takes a contemporary building which utilises modern construction methods, whilst reclaiming the Malvern stone for the external cladding, in a way to tie the project with the surrounding landscape and context.
Conclusion: Make material decisions early
Natural materials look better, feel better and age far better than their synthetic counterparts. It’s important to work with someone who carefully picks out the right material and that this process is considered early on.
How we can help
We are a RIBA Chartered architect based in Birmingham but working across the UK. If you are interested in how we approach selecting materials and would like to have a conversation, you can email me, peter@markosdesignworkshop.com or use the link above to book a free call
