19 September 2017

Benefits of building with cob, plus examples (#SuperNaturalMaterials 8)

This is the eighth post in our Super Natural Materials series - you can view the whole series here.

What is cob?

Cob is a mixture of sandy-sub soil, clay and straw. It's mixed by crushing the particles together by either dancing on it or using the head of a digger. The sandy-sub soil must be sharp and ideally contain angular stones and gravel - this will make it stronger. About 75% of cob is made up of this sandy aggregate. Any type of clay can be used, but be careful not to use silt which can sometimes appear like clay.

It's a strong and durable material - houses can last for a very, very long time - if maintained and looked after properly. The oldest standing cob house is reportedly 10,000 years old.

In places where timber was scarce, the building material most available was often the soil underfoot - local and natural materials were and still are, the cheapest and one of the most sustainable ways to build. Cob construction is easy and doesn't require any fancy equipment or specific training. Its thermal performance varies by climate region - while cob is a relatively poor insulator, it also has the ability to absorb larger quantities of heat.

Benefits of building with cob:

  • Sustainable - the most sustainable form of building there is - cob has almost zero embodied energy. Since its made of earth, it his also entirely recyclable and non-polluting.
  • Affordable - as long as you have land to build on, anyone can afford to build cob walls.
  • Breathable - its a healthy place to live, as there is no damp in a cob house.
  • Requires almost no heating - if you design your cob house on passive solar principles, you can get around its poor insulation properties. To do this, you should use cob on south facing walls, making the most of its thermal mass. Then, us e straw bales on the north facing walls to provide great insulation.
  • Aesthetics - with cob, you can practically sculpt it, meaning that you can create curves and even carve shelves into the walls.
  • No chemicals or additives 
  • Sustainable load bearing
  • Long life spain
  • Recyclable
  • Biodegradable
  • Doesn't burn
  • Insects will not eat cob

 Examples of building with cob:

Cob Cottage: "A cob cottage in the West Country, where the soil has the ideal proportion of clay required for this method of construction; A cob inglenook, with an attractive uneven finish, houses a wood-burning stove." via Period Living.

building with cob, natural materials, construction, Koru Architects

Image credit: Period Living

Keppel Gate: "Keppel Gate is situated at the end of a long no-through lane, just outside the East Devon town of Ottery St Mary, which is one of the oldest and most historic small towns in Devon." via BuildSomethingBeautiful.

building with cob, super natural materials, koru architects, eco architect, sustainable architect

Image Credit: BuildSomethingBeautiful

Hobbit Hole: "A farmer built this cottage for just £150, using only natural or reclaimed materials, and is now rented out for a fee of fresh milk and cream. And with no mains electricity, gas or water, the bills don’t come to much either." via BBC.

building with cob, super natural materials, koru architects, eco architect, sustainable architect

Photo Credit: Michael Buck

Want more articles like this? Subscribe to our monthly newsletter

And let us know what you think about building with cob at @KoruArchitects with the #SuperNaturalMaterials hashtag.

12 September 2017

Benefits of building with straw, plus examples (#SuperNaturalMaterials 7)

This is the seventh post in our Super Natural Materials series - you can view the whole series here.

How do you use straw in construction?

Straw-bale construction is a building method that uses bales of straw as structural elements, building insulation or even both – it's a sustainable method for building, from the standpoint of materials and energy needed for heating and cooling. The construction typically consists of stacking rows of bales, often in running-bond, on a raised footing or foundation, with a moisture barrier or capillary break between the bales and their supporting platform.

Bale walls can be tied together with pins of bamboo or wood, which add to the sustainability factor of the material. Alternatively, you can use wire meshes, then plaster either with a lime-based formulation or earth/clay render. Bale buildings can have structural frames of other materials, too – bales can simply serve as insulation.

Compressed straw bales have a wide range of documented insulation values. R-Value is a measurement of a material's insulating quality – the higher the number, the more insulating. The reported R-Value ranges from 17-55 (in American units). Bale walls are typically coated with a thick layer of plaster, which provides a well-distributed thermal mass.

 Benefits of building with straw:

  • Made from waste product - once the edible part of the grain has been harvested, the bales of straw give a new life to the material.
  • Great insulation - the thicker the bale, the better the R-Value.
  • Low-embodied energy - very little energy goes into the manufacturing of the product. Sunlight is the main source of energy for the plant.
  • Biodegradable - straw bales are 100% biodegradable; homes made from straw can last over 100 years if maintained properly and when the time comes, the straw bales can be plowed back into the earth.

Examples of building with straw:

building with straw, super natural materials, koru architects, eco architect, sustainable architect

BaleHaus at the University of Bath. Photo credit: University of Bath

BaleHaus at the University of Bath

"BaleHaus is an innovative two-storey straw building, constructed on campus using ‘ModCell’ - pre-fabricated panels consisting of a wooden structural frame infilled with straw bales or hemp and rendered with a breathable lime-based system. The system delivers a sustainable method of construction, combining the lowest carbon footprint and the best operational CO2 performance of any system of construction currently available. Straw offers the perfect material for environmentally friendly construction due to its renewable nature. Monitored for two years for its insulating properties, humidity levels, air tightness and sound insulation qualities, the research team established that the building maintains heat through very cold winters, stays dry and produces good sound insulation." - University of Bath


building with straw, super natural materials, koru architects, eco architect, sustainable architect

Quiet Earth Retreat Straw Bale House. Photo Credit: Self Build Central UK


Straw House in Pembrokeshire 

This home, situated in St Dogmaels on a woodland hilltop, overlooking breathtaking views of the Cardigan estuary in Pembrokeshire was the winner of the Grand Design Eco Home Award in 2008. Nicknamed Quiet Earth Retreat, is boasts two storeys and is an off-grid home, powered by the sun and wind. The home is an all-round sustainable property.

You can even book to stay at this home, here.

building with straw, super natural materials, koru architects, eco architect, sustainable architect

NO99 Straw Theatre. Photo Credit: ArchDaily



NO99 Straw Theatre

In 2011, Estonian studio Salto Architects completed a temporary summer theatre in Tallinn made of black spray-painted straw bales. The stage was put into place for six months to celebrate the city's status as 2011's European Capital of Culture.

Want more articles like this? Subscribe to our monthly newsletter here. And tell us your thoughts about building with straw at @KoruArchitects using #SuperNaturalMaterials

3 August 2017

Benefits of building with bamboo, plus examples (#SuperNaturalMaterials 6)

This is the sixth post in our Super Natural Materials series - you can view the whole series here.

building with bamboo, super natural materials, koru architects, eco architect, sustainable architect

How can you build using bamboo?

Bamboo is a type of grass, with a hard, hollow stem. It is a perennial evergreen: it grows every year and stays green year around. There are hundreds of kinds that grow in different regions pf the world – the plant has versatile usage, from medicine to construction.

Bamboo is one of the most versatile and sustainable natural building materials available, when treated correctly. With nearly 1500 different species of bamboo, not all are able to be used in construction, only a handful of the huge collection of species are durable enough for construction, to name a few: guadua, dendrocalamus and phyllostachys.

building with bamboo, super natural materials, koru architects, eco architect, sustainable architectOne of the more commonly used species, Guadua, produces vast amounts of biomass and absorbs CO2 very quickly, thanks to its fast growth rate and short maturation cycle. Growing up to 85 feet in height and eight inches in diameter, it can be used in construction after reaching maturity within four years. Guadua is capable of absorbing six times more CO2 when compared to Oak over a 50 year period. An insightful read regarding bamboo and its uses can be read here, referencing World Bamboo Ambassador Hector Archila Santos' research on the plant.

Being a versatile resource, it can be utilised for permanent and for temporary construction. Not only does it boast strong performance through its weigh and strength advantages, but it's aesthetically pleasing. With its smooth, clean and attractive finish there's no need for painting, polishing or any form of decoration.

As a natural resource, it's not perfect – it needs treatment. With high levels of starch, it can attract insects such as termites and powder-post beetles. However, these are minor issues as it is the norm to treat bamboo before using it for construction.

There are two ways to treat bamboo – with or without using chemicals.


The non-chemical, traditional methods include smoking and white washing. Smoking is carried out in chambers, where to heat destroys the starch in bamboo, this making them immune to insect attack. White washing sees bamboo being painted with slaked lime, which reduces moisture absorption.


Chemical treatment is less sustainable, but more effective than the traditional treatments. Typical chemical treatment methods uses water soluble preservatives like Gamma BHC 0.5%, Formalin 0.5% , Phenol+ 1 Copper sulphate (1: 2), sodium penta chlorophenate 0.5% and Borax 1.5%. The chemicals are dissolved in water, then the bamboo is either sprayed with the solution or dipped in it for around 10 minutes.

Benefits of building with bamboo:

Non-pollutingit does not have any crusts or parts that can be considered waste. Any part of bamboo which is not used is recycled back into the earth as fertiliser or can be processed as bamboo charcoal.

◦ Light building material, it is circular and hollow, meaning that it is easy to handle, transport and store.

◦ Stable, in each of its nodes, bamboo has a dividing or transverse wall that maintains strength and allows bending, thus preventing rupturing when bent. This means that bamboo has superior earthquake resistance.

◦ Fire resistant (to an extent), it can withstand heats up to 4000 degrees celsius, due to its high value of silicate acid and water.

◦ Tensile strength, bamboo has a higher tensile strength than steel because its fibres run axially.

Examples of building with bamboo:

building with bamboo, super natural materials, koru architects, eco architect, sustainable architect

Guadua Bamboo Car Park in Amsterdam. Photo Credit: guaduabamboo.com

Bamboo Car Park in the Dutch Capital

Guadua bamboo was used as the exterior wall cladding to add natural and sustainable elements to this project, just outside of central Amsterdam. The first level of the car park has been left naked, without any bamboo poles, but just the greenery of the bamboo plants which amplifies the visual aspect of the bamboo structure above.







building with bamboo, super natural materials, koru architects, eco architect, sustainable architect

Bamboo Clad House. Photo Credit: Luca Tettoni

House in the Philippines 

Bamboo poles were used to clad the exterior of this family home, showing off its natural look, contrasted and matched with the use of glass. When asked about building with bamboo on this project, the architects said:

"It is a low cost and sustainable material that grows intensively locally. This material has been historically used in the country for the fabrication of handicrafts, native architecture and utilitarian objects."






building with bamboo, super natural materials, koru architects, eco architect, sustainable architect

Wind and Water Bar in Vietnam. Photo Credit: Vo Trong Nghia and Phan Quang

Wind and Water Bar

This thatched bamboo dome sits in the middle of a lake, in Binh Duong Province, Vietnam. The structure of the building exhibits bamboo's ability to be bound and bent together to form arches.






building with bamboo, super natural materials, koru architects, eco architect, sustainable architect

Wind and Water Bar in Vietnam. Photo Credit: Vo Trong Nghia and Phan Quang

Want more articles like this? Subscribe to our monthly newsletter here. You can chat to us about building with bamboo using the hashtag #SuperNaturalMaterials

6 July 2017

Benefits of building with hemp, plus examples (#SuperNaturalMaterials 5)

This is the fifth post in our Super Natural Materials series - you can view the whole series here.

building with hemp, super natural materials, koru architects, eco architect, sustainable architectHemp: a versatile material

Hemp is a plant that holds extraordinary history, from its use as paper, to hemp plastic, to its versatile uses in the construction industry. Natural building materials require minimal refining and processing, while simultaneously reducing the detrimental impact the construction industry has on the environment.

France is one of the countries to truly embrace and endorse the use of hemp in construction; for years it has been used as the material of choice in the conservation of timber frame buildings.

After processing the stems of the plant, two different materials are produced: hurds and fibers.

Hurds can be turned into products such as roofing tiles, wallboard, fibreboard, insulation, panelling, bricks and more recently, structural timber/hemp building blocks.

Fibers, on the other hand, are used in place of straw for bale wall construction or alternatively can be blended with mud for cob style construction.

For those asking – no, you can’t smoke it. The cannabis plant is resourceful in many ways and hemp happens to be one of them. This post will explore some of the top benefits of building with hemp, plus some examples of diverse hemp projects from our work and other designers.

 Benefits of building with hemp:

building with hemp, super natural materials, koru architects, eco architect, sustainable architect

Entrance to a hemp-built house in Israel. Photo credit: Tav Group/Yaeli Gavrieli

◦ Low embodied energy – doesn’t require much processing in its production, meaning that it is beneficial to the environment.

◦ Carbon storage – in its lifespan, it absorbs a large amount of CO2 from the atmosphere. During its growth stage, it will lock away up to 2 tonnes of CO2 per tonne of fibre harvested.

◦ Great thermal insulation properties – it's a medium density insulation material which is safe, efficient and durable. Low conductivity and a higher thermal mass enable it to retain heat and regulate thermal performance for a comfortable internal environment.

◦ Breathes, prevents condensation – it can absorb up to 20% of its weight in moisture without deterioration in its performance, unlike most other insulation materials. It can then release this moisture when required, regulating the internal humidity. Hemp is also mould-resistant.

◦ Non-flammable – when mixed with lime in Hempcrete construction, it is completely non-flammable.

◦ Lightweight – which increases its range of applications in the construction industry, can be used in lofts, walls and inter-floors.

◦ Recyclable – it’s biodegradable and non-toxic so it’s truly circular – it can completely decompose.

◦ Sustainable – hemp can be grown year-round and only takes up to 100 days to reach full growth.

◦ Low maintenance – it requires very little water to grow and does not require herbicides or chemical pesticides.


Examples of building with hemp:

building with hemp, super natural materials, koru architects, eco architect, sustainable architect

Marks & Spencer's Cheshire Oak Store

Opened in August 2012, M&S Cheshire Oaks has won multiple awards and is their biggest, greenest store. It has been designed to be the most carbon efficient store of theirs to date with an architectural and design strategy to address various areas of sustainability at once. It is the first store to use hemp and lime external wall panels which have excellent insulation properties resulting in the store losing less than 1°C of heat overnight compared to 9°C in other store environments.

[tweet https://twitter.com/IndustrialHemp/status/700349913142534149]

America's first hemp house in Asheville, North Carolina. The house is made with hempcrete and boasts an abundance of eco-friendly features. Using hempcrete allows a solid yet breathable wall. Hemp hurds were mixed with lime and water on-site and poured in-between the exterior supporting timber studs.

building with hemp, super natural materials, koru architects, eco architect, sustainable architect

Photograph: Tom Woolley

Hemp Cottage in County Down, Northern Ireland. Shortlisted in the Top 10 UK Eco-Homes, the house's main frame was built from locally sourced Douglas fir, with the stud work being cast with a hemp lime composite. Explore more about this home here.

Why do architects like working with hemp?

"It's a natural insulation material; it's hygroscopic, so has the ability to hold onto moisture, which allows it to act as a humidity regulator and of course, it's recyclable, that's why I used it on my house for insulation."

-  Mark Pellant, Director of Koru Architects

Want more articles like this? Subscribe to our monthly newsletter here. Chat to us about building with hemp using #SuperNaturalMaterials

20 April 2017

Benefits of building with stone, plus examples (#SuperNaturalMaterials 4)

This is the fourth post in our Super Natural Materials series – you can view the whole series here.

building with stone super natural materials Building with stone: a long history

From smart townhouses to grand mansions to medieval castles to cosy worker cottages to ancient temples, building with stone stretches back to prehistoric times. It’s one of three oldest building materials along with timber and clay. Stone is frequently used in residential projects as solid stone walls, or stone cladding, or tiles and counter tops. Like other natural materials in this series, stone is beautiful, low carbon and non-toxic. But where stone really excels is in its’s intense longevity.

This post will explore some of the top benefits of building with stone, plus some examples of diverse stone projects from our work and other designers.

Benefits of building with stone

  • Extremely durable and resilient to wind, fire, water, rot and bugs. It’s maintenance free – there’s no painting, oiling or replacing to do and it’s very hard to damage. The oldest human built structures still standing on Earth are made of stone. It’s so durable that perhaps ‘permanence’ is a better term.
  • building with stone

    Oakdene Passiv House, one of our projects. Uses traditional Sussex sandstone.

    Naturally beautiful with diverse shapes, textures and colours to choose from. Stone is readily available in most regions, with regionally distinctive stone contextualising the local vernacular and culture.

  • Good insulation because of its extremely high thermal mass which is a good insulator in temperate climates. The stone slowly heats up in the day and releases its warmth in the night. Needs passive solar design to be most effective and can be too cold in cooler climates.
  • Natural and non-toxic, no off-gassing of VOCs or chemicals to worry about, making for cleaner air in your home and better health and wellbeing.
  • Low carbon, requiring very little processing so the production process is lower in energy and carbon than most building materials. The global availability means lower shipping emissions than more specialist materials. Stone is finite but reusable.

Examples of building with stone

Koru projects

building with stone

Bannerlands, one of our projects with several rural homes made of stone and timber.

Local Sussex sandstone was used for the walls of this rural eco-house, built to passivhaus standards with environmental technologies and a beautiful spacious site.

This development of 5 rural village homes, grouped together like a small farmstead, is comprised of timber and stone walled houses. This alteration adds interest to the development while both suit each other and blend into the landscape.

South Street
On this contemporary crescent-shaped riverside house, the street-side of the ground floor is clad with flint, a locally occurring kind of natural stone.

Other projects

Here are just a few examples of other stone residential projects, showing the wide variety of styles that can be achieved with stone. Despite its ancient roots it can easily be used for contemporary design.

Very modern contemporary home with stone cladding on the exterior and interior walls and floors. Features an indoor private pool, with the pool room clad in cool stone.

Traditional rural stone cottage with a timber frame. These kind of houses are common throughout the English countryside.

The rustic stone of the walls beautifully compliments the contemporary interior design of this home for a unique look.

This traditional stone house has a contemporary glass extension, with the two styles contrasting each other effectively.

Want more articles like this? Subscribe to our monthly Eco-Design Newsletter here >>

And let us know what you think about building with stone at @KoruArchitects with the #SuperNaturalMaterials hashtag.

22 March 2017

Benefits of building with clay, plus examples (#SuperNaturalMaterials 3)

This is the third post in our Super Natural Materials series – you can view the whole series here.

building with clay, super natural materials, koru architects, eco architect, sustainable architect

The versatility of clay

The use of clay dates back to the earliest human civilisation and clay bricks have been a popular building material since the Babylonian civilisation in 3000BC. The naturally malleable fine-grained earthy material is incredibly versatile, used for ancient writing tablets, cooking pots and kitchenware, artwork and, of course, for building.

Because of its strength, durability and abundance – among other benefits – bricks and tiles made of clay are some of the most popular building materials ever. As well as its historical use, building with clay has undergone a resurgence in recent years following more public interest in sustainability, health and artisan craftsmanship.

In this post, we’ll explain our top 5 benefits of building with clay and offer examples of clay building from our own work and the work of others.

Benefits of building with clay

  • building with clay, super natural materials, koru architects, eco architect, sustainable architect

    Tichborne Street mixed use development with red linear or Roman bricks


    Clay rivals wood in its amazing versatility. In building it is used to make bricks, tiles and plasters, as well as the low-impact natural building materials adobe, cob, rammed earth and wattle and daub. Bricks can be fired or unfired. Tiles can be used on roofs, floors, or walls. Clay plasters can come in different textures, colours and finishes.

  • Durable

    A house made of bricks will last for generations. They are expected to last at least 100 years, but many have lasted far longer than that. They are also very low-maintenance, are resistant to both fire and water and don’t rot or rust.

  • Insulating

    Clay has excellent insulating properties because of its high thermal mass. It absorbs, stores and releases heat very effectively, making the building interior cooler in summer and warmer in winter. This makes the internal environment more comfortable and also reduces energy demand and associated carbon emissions. Even a 15mm clay plaster coating will have a significant insulating effect.

  • building with clay, super natural materials, koru architects, eco architect, sustainable architect

    Portland Villas 11 houses with red brickwork and timber


    With careful deconstruction bricks and tiles can be reused in other projects. As they don’t need to be melted down into base material and can be reused as they are it is an extremely low-energy method. Clay also has the ability to be easily reformed when wetted, so other clay materials can be recycled. As a natural non-toxic material it can also be safely and ecologically returned to the Earth and never needs to go to landfill. As a finite material, albeit an extremely abundant one, it is key to the future circular economy that it can be recycled.

  • Healthy

    Clay also has significant health benefits over other materials because it is completely natural, non-toxic and inert, with no VOCs or chemicals off-gassing from the material. As well as regulating temperature, clay is also a humidity regulator. This not only makes a more comfortable environment, it prevents mould and fungal growth in the home. All this creates a superior internal air quality which is important for health, especially when you consider that people in Europe and America spend around 90% of their time indoors.

Koru projects showing use of clay

Tichborne Street

This mixed-use development of flats and workshops in the heart of Brighton utilised linear of ‘Roman’ bricks which are longer and shorter than traditional bricks. The striking red brickwork coupled with the large grew-rimmed windows fits into the local style yet also looks fresh and contemporary and adds colour to the street.

building with clay, super natural materials, koru architects, eco architect, sustainable architect

Highlands Road house with reddish brown brickwork

Portland Villas 11

These two semi-detached family homes are made with a traditional palette of red clay bricks and timber, which suits the local vernacular of the street and fits in with the neighbouring properties. The traditional familiarity of the brickwork softens the contemporary form and detailing of the properties.

Highlands Road

This detached house is a contemporary reimagining of an Arts and Crafts style house, and the natural materials of clay and zinc are a key part of that design philosophy. The design utilises interior clay tiles and external reddish brown brickwork, which adds a traditional feel to the more contemporary zinc roof.

Other examples of building with clay

Given the enormous potential of building with clay, it’s hard to choose just a handful of examples. Here’s a few interesting ones to show some of the diversity available.

In this beautiful restaurant setting, clay plaster is used to create a feature wall rich with pattern and texture. The sculptural properties of clay mean you can create bespoke finishes that are impossible with paint.

This simple matte clay plaster combines with the whole timber, rounded walls and wood stove to create a rustic cosy interior. Contrasts with the restaurant above which is more contemporary chic.

The durability and versatility of clay floor tiles means as well as for interiors they can be used outside as well, like in this beautiful walled garden. They have used unusually shaped tiles to create a pattern.

Clay brick is generally considered a traditional material best suited for traditional styles of architecture. But that doesn’t need to be the case. Here, dark brown clay bricks are used to build a very quirky house with a very unusual playful form.

Want more articles like this? Subscribe to our monthly Eco-Design Newsletter here >>

And let us know what you think about building with clay at @KoruArchitects with the #SuperNaturalMaterials hashtag.

2 March 2017

‘Building Places That Work For Everyone’ Report Launch

Issi Rousseva with Julie Hirigoyen: building places that work for everyone

Issi Rousseva with Julie Hirigoyen, CEO of UKGBC

With the right combination of industry expertise, community engagement and a clear steer from government, we can build places that work for everyone.

That's the headline message of the UK Green Building Council's new report: Building Places That Work For Everyone. Koru's architect Issi Rousseva attended the policy paper launch on 28th February 2017 at the Houses of Parliament. The launch event was chaired by Julie Hirigoyen, CEO of the UK Green Building Council, and also included talks by industry leaders and politicians George Freeman MP, Stephen Kinnock MP and James Heappey MP.

Issi particularly enjoyed the talk by Dan Labbad, CEO of Lendlease, a global property and infrastructure company. Dan spoke about how to be successful, sustainability must be right at the core of business operations - never an after-thought simply to tick boxes. Issi also enjoyed speaking with Mark Harper MP about the potential of the circular economy, and she was interested to note that many of the delegates were relatively new to sustainability but were determined to make a difference in their own businesses and organisations. This is a welcome change from the tendency of green events to be full of experts and long-time enthusiasts 'preaching to the choir'. This highlights the fantastic outreach and engagement work the UK Green Building Council have been doing.

The report covers how sustainable building can contribute to key government priorities around homes, energy, industry, jobs and social wellbeing. It also contains best-in-class example projects, insights from industry leaders, key statistics and practical policy recommendations. Koru Architects supports their recommendations and we hope to see the government using this paper to inform more effective policymaking.

23 February 2017

Benefits of building with zinc, plus examples (#SuperNaturalMaterials 2)

This is the second post in our Super Natural Materials series - you can view the whole series here.

building with zinc, super natural materials, koru architects, eco architect, sustainable architectWhat is zinc used for?

Zinc is an abundant, lightweight and shiny metal which has long been used in construction for roofs and vertical cladding. It is perhaps most extensively used in Paris, where the majority of roofs have been zinc since Napoleonic times. It's currently becoming more popular for civic and corporate buildings that need to last a long time, as well as increasingly for homes as its sustainability benefits gain prominence.

This post will outline the benefits of building with zinc, plus several examples of the kinds of buildings that utilise it.

Benefits of building with zinc

building with zinc, super natural materials, koru architects, eco architect, sustainable architect

Lloyd Close eco-house with zinc roof

  • Very durable
    Zinc roofs can last more than 100 years because it doesn’t rust, instead it ‘heals’ itself with a protective patina that comes back after scratching. It's formally known as zinc hydroxyl-carbonate. By comparison, clay or concrete tiles are expected to last 60 years. Because of the protective patina, zinc is not sensitive to rust or UV and is very low maintenance. This counteracts the high initial cost.
  • Non-toxic
    Zinc is a fungistat that prevents build-up of mould or moss and its water runoff is not toxic to plants, unlike copper which is fungicidal but also harmful to plants. Illustrating its lack of toxicity, zinc is actually a micro-nutrient, present in the bodies of people and animals and required in small quantities for optimum health.
  • Sustainable
    While not renewable, this finite metal is extremely abundant compared with other resources. In fact it’s the 24th most abundant element in the Earth’s crust. Estimated zinc ore reserves are 34 million tonnes, enough for 700 years at present rates, not taking recycling into account. And it is almost entirely recyclable, so with smart circular economy processes we should be able to make it last indefinitely. Even mining and processing zinc ore is much less energy-intensive than other metals because it is lightweight and has a low melting point. As VMZINC, a leading zinc supplier, tells ArchDaily:

    “A big sustainability advantage for zinc over other metals is that it takes much less energy to refine zinc than aluminum, copper, or stainless steel. For instance, the energy required to produce zinc from ore is a quarter of that needed to make aluminum and half of that needed for copper and steel.”

  • Very flexible
    Zinc can be cut, curved and folded to produce interesting shapes – one of the properties which has made it so popular with architects. It’s very malleable, lightweight and soft, yet also strong. Suitable for all roof pitches between 5% - 90%.
  • Aesthetics
    Undoubtedly a key reason for zinc’s popularity is its natural beauty. The material is a smooth and shiny silvery colour. As it weathers, it develops an attractive dappled patina (which also protects it, see above). Alternatively you can buy it pre-weathered or coloured, allowing even more creative designs with two or more shades.

Examples of building with zinc

building with zinc, super natural materials, koru architects, eco architect, sustainable architect

Oakdene passivhaus with zinc roof

Projects using zinc designed by Koru Architects

For the reasons above, we often utilise zinc for roofing of our projects. Here’s three examples.

Lloyd Close
This award-winning zero-carbon detached house and studio is our director’s home and also houses the Koru Architects company office.

Winner of the RIBA Downland Prize 2011 and the Green Apple Award for Architecture 2016. Natural materials which are low in embodied energy have been used throughout, including hemp insulation, oak cladding, zinc roofing and lime render. The living room roof also features a green sedum roof.

If you like this project, you can subscribe to our newsletter for a PDF case study of the project and all its sustainability features.

Oakdene Passivhaus
This detached rural home built to passivhaus standards sits on an agricultural smallholding in the Sussex countryside. The house is constructed from natural materials low in embodied energy including local Sussex sandstone, Sweet Chestnut timber cladding, zinc roofing and sheep’s wool insulation.

building with zinc, super natural materials, koru architects, eco architect, sustainable architect

Highlands Road house with zinc roof

Highlands Road
This 4-bedroom property is a contemporary low-energy reimagining of an Arts and Crafts style house. The design uses a palette of natural and traditional materials such as brickwork, clay tiles, zinc and a timber frame.

Other zinc architecture projects

Given the flexibility of zinc, it can be utilised for a very diverse range of buildings. Here are just a few more examples...


An example of a contemporary building with ribbed zinc cladding coming down from the roof to the ground, covering the whole exterior.

This is a classic grey zinc roof with zinc cladding coming part way down the wall of the larger wing of the house.

Finally, here's a very unusual curvy roof made with zinc, showing its extraordinary flexibility.

Want more articles like this? Subscribe to our monthly Eco-Design Newsletter here >>

And let us know what you think about building with zinc at @KoruArchitects with the #SuperNaturalMaterials hashtag.

26 January 2017

Benefits of building with timber, plus examples (#SuperNaturalMaterials 1)

This post is the first in our Super Natural Materials series.

building with timber, super natural materials, koru architects, eco architect, sustainable architect

Is the world's oldest building material also the most advanced?

Timber: a popular choice

Timber is one of the most popular building materials and people have been building with timber since ancient times. Its great versatility means it’s used in all areas of construction, architecture and design – from structural frames to finishes to furniture and artwork. Timber may be the only material where you could design a whole house with every element made out of timber. We believe it’s one of the very best materials, so we utilise it in the majority of our projects.

Wood is the oldest building material, yet development of Cross Laminated Timber (CLT) has given it a whole new innovative appeal. As Rethink Wood explain:

Cross-laminated timber (CLT) is a wood panel typically consisting of three, five, or seven layers of dimension lumber oriented at right angles to one another and then glued to form structural panels with exceptional strength, dimensional stability, and rigidity. ... Since CLT panels resist high racking and compressive forces, they are particularly cost effective for multi-story and long-span diaphragm applications.

The twin trends of population growth demanding greater urban density and more concern about sustainability, mean timber is getting ever more popular as a building material – even for high-rises. As this story in Popular Science puts it:

The world’s urban future may just lie in its oldest building material.

We're going to outline why it's such a great material, and then offer a few examples of the diverse range of buildings that can be built with timber.

Benefits and strengths of building with timber

building with timber, super natural materials, koru architects, eco architect, sustainable architect

Lloyd Close zero-carbon home and office, built with CLT timber structure and timber cladding

To learn more about the benefits of building with timber, check out our previous article ‘13 Ways Sustainable Timber Is The Best Construction Material’. Here’s our top 5:

1. Versatile

As well as being naturally beautiful, wood is also extremely versatile. Different species of tree produce timber of differing colours, textures and functional qualities. Wood also competes with plastic in its enormously wide range of applications: from structural frames to exterior cladding and joinery, and from decorative finishes to furniture.

2. Durable

Timber is a highly durable material. Some well-made wooden structures last for centuries, such as the timber frames of many Tudor buildings. It is also easy and cheap to maintain compared to other materials, especially if you don’t mind it changing its colour over time. As a very strong material with good structural properties, it's suitable for up to eight storey buildings (and new innovations are now even allowing timber to be used for high-rises!) It also has good fire resistance. This sounds surprising, but it burns in a much more predictable way than steel – which dramatically collapses after a ‘flash point’ is reached.

3. Non-toxic

In its natural state wood is completely non-toxic and healthy. It can sometimes be treated with toxic preservatives which can off-gas and prevent the wood from being safely burnt or composted, although this isn’t strictly necessary and with careful specification of durable timber, wood can often be used untreated. Advances in green chemistry mean more non-toxic glues and preservatives are being developed all the time. Even ‘conventional’ chemicals have been improved in recent years so off-gassing is now minimal.

building with timber, super natural materials, koru architects, eco architect, sustainable architect

Garden office made entirely out of timber, with recycled newspaper insulation

4. Carbon Storage

With sustainable forestry, at least as many new trees are grown than are harvested. As long as a timber product does not burn or rot its carbon stays ‘locked up’. So when trees are harvested, their carbon is stored in timber and they are replaced by new young trees, therefore the net effect is removing carbon from the atmosphere – which is good for the climate.

5. Renewable

Looking to the longer term, one of the biggest advantages of building with timber is that it is obviously a naturally renewable material. A tree can be grown to a suitable harvest size in 25 to 80 years, while the raw materials for bricks, steel and plastics are only renewed over geological time – i.e finite in human terms.

Examples of timber builds

Our projects

Lloyd Close
This detached 3-bedroom home and office is net zero-carbon, generates more energy than it uses, and has won two awards. Timber is used extensively throughout. The structure utilises Cross Laminated Timber (CLT), an innovative timber product with superior strength and structural durability. The exterior walls are clad with timber panels, and timber flooring is used throughout the property.

Garden Library
This sustainable, all-timber garden workspace has been designed for working in light and comfort with minimal heating or artificial lighting. Glazed timber sliding/folding doors and a roof-light flood the internal space with light and help with space heating. The timber frame is fabricated from Douglas Fir and the cladding from Western Red Cedar.

These are just two examples of building with timber. We incorporate timber in the majority of our residential and commercial projects, and we always work to ensure our timber is sustainably sourced.

Other projects

As one of the world's most popular building materials, there are countless examples of timber buildings. Here's just two examples of what can be achieved.

High-rise towers of glass, concrete and metal are a familiar sight in cities around the globe. Now, technical advances and materials innovation means skyscrapers can now be built with Cross Laminated Timber (see above). This one is scheduled for construction in Amsterdam in the Autumn of 2017. It will be a towering 240 feet tall.


This contemporary Scandinavian townhouse is made from CLT and glue-laminated pine, and it leaves the timber interior exposed to give the impression of the home being carved out of wood. The five-storey property is spacious, yet fits into a compact narrow plot.

What's your favourite use for timber? And what other natural materials do you want us to cover? Tweet us your ideas at @KoruArchitects using the #SuperNaturalMaterials hashtag.

20 July 2016

Renovate or rebuild? Creating your dream home

It’s a classic dilemma. You’ve purchased a scrappy run-down property in a fantastic location, with the plan to knock it down and build your dream home, but now you’re wondering if actually a major renovation will do the job.

Or, perhaps you’re thinking of your current home, which is in bad shape. You’ve been planning an extension, remodel of the main living rooms and a new fittings throughout. Now you also want to move the staircase and one of the external walls which has always suffered from damp, and you’re now thinking: wouldn’t it be better to just start again from a blank canvas?

Many homeowners are faced with this life-changing decision at some point in their life. When it comes to your biggest asset, is it better to renovate or rebuild?

renovate or rebuild, koru architects, eco architect

Does your property look like this? Photo by Nolan Isaac (Creative Commons).

The quick answer is: it depends. Clearly there can be no clear cut answer to this design dilemma, because there are so many factors and every case is unique. But obviously that answer is entirely unhelpful, so this article will outline some of the major considerations and give some general advice to help you decide.

There’s lots of moving parts when it comes to the renovate vs rebuild question. The major considerations we’ll be discussing are design freedom, structural quality, financial cost, planning permission and sustainability.

However there are also other important things to consider that we can’t cover here, like:

  • emotion (do you or your family have an attachment to the house?)
  • logistics (where will you live while the work is being done?)
  • comfort (it's usually cheaper and easier to achieve thermal comfort with a new build)
  • convenience (how much do you hate your life being turned upside down?)

Also, perhaps the biggest consideration is how big a change you want. Simpler changes (e.g. an extension plus full redecoration and new windows) clearly point to a renovation, whereas if you want to change so much that hardly anything would be left untouched then a rebuild is likely better. We’ll assume it’s somewhere in the middle, where deciding to renovate or rebuild could both work.

Renovate or rebuild: consider your priorities

Design Freedom (rebuild unless historic merit)

Of course, the end goal here is to end up with a home which is not only comfortable and suits your lifestyle, but which looks the way you want it to look. The big questions are: does your house have historical or architectural charm? How far is the existing style and layout from what you want? The more merit the existing building has the more you should opt to renovate, and the further away from what you want it is, the more you should consider a rebuild. One of the main reasons for rebuilding is usually the design freedom it affords – the opportunity to design a home which suits your family perfectly.

renovate or rebuild, koru architects, eco architects

CLT timber construction for our zero-carbon home-office.

Structural Quality (renovate unless poor structure)

Clearly if the structural quality is so poor it’s verging on unsafe then either a rebuild or a very large-scale renovation is needed ASAP.

A renovation can work here, but as renovations usually leave the core structure in place, this consideration does nudge you towards rebuilding if the structure is poor or if your house is plagued by chronic damp problems.

Structural changes during a renovation are very expensive. On the other hand, if the underlying structure is sound and the changes you want are mostly cosmetic, renovation is better. The structural elements of the building are expensive and high-carbon.

Financial Cost (rebuild)

It’s usually cheaper to demolish and rebuild than to undergo a full whole-house renovation. This isn’t necessarily what you’d expect, but it’s usually the case. One reason is that while renovation work has standard (20%) VAT, building a new home is 0% VAT, via a rebate. This is a considerable saving.

Secondly, it’s very common to underestimate the amount of work needed on a full-house renovation. As this article explains, ‘small fixes become big fixes’, builders discover nasty surprises while working and costs can quickly spiral out of control. A new build is easier to plan and budget accurately.

If you do go that route, demolition and removal will cost between £3,000 - £10,000 depending on the size, if there’s any hazardous waste and if you’re reclaiming anything. Or, if you’re renovating a house which has been empty for two years or more, you can do it up with a reduced rate of 5% VAT.

Planning Permission (renovate)

The planning hurdle will be far higher for a rebuild, as it will be required to meet all modern building standards while renovating a non-compliant building is accepted as long as it doesn’t make its non-compliance even worse. Such standards include energy efficiency levels, wheelchair accessibility plus all kinds of rather detailed requirements you wouldn’t expect.

There’ll be far more time spent on paperwork with a rebuild, and you could be forced to adapt your plans.  A key factor is the type of house and the area. If it’s in a conservation area planning is more difficult. If you have a Victorian or Edwardian townhouse you will meet resistance to demolition, and if it’s a Listed Building you’ve got next to no chance of knocking it down.

With historic buildings, sometimes keeping the front facade and reconstructing everything else is acceptable to planners. A couple of examples from our work may help illustrate the planning issues. Mill Lane was a new build because the planners wouldn’t approve of a two-storey enlargement of the existing bungalow whereas Garden Cottage was an extension/renovation because of the sensitive site and the need to preserve the existing cottage.

Environmental Sustainability (renovate unless replacing a very inefficient home with a zero-carbon one)

In general, working with what you’ve got is greener than replacing it. There are two types of energy (and associated carbon emissions): embodied and operational. Operational is energy used in your daily life within the house. Embodied is the energy it took to construct the house and to manufacture and transport the materials that went into it. The embodied energy is huge, and demolition usually results in a mass of rubble being thrown in landfill. This means if you're deciding whether to renovate or rebuild based on environmental sustainability, renovation is usually the greener choice.

However, there are some cases where replacing an extremely inefficient house with an extremely efficient one has a positive environmental impact, when you consider the longterm. This Eco Vision article estimates that replacing a house with a new one which is 30% more efficient than the average will take 10 - 80 years to offset the carbon used in construction. That’s quite a range – 10 years is a brilliant carbon payback period while 80 years is definitely not worth it ecologically, considering building lifespans are assumed to be about that long. But importantly, it is very doable to make a house way more than 30% more efficient than the national average.

For example, our eco home-office emits 93% less carbon than the average. Also, some of the embodied carbon can be clawed back by salvaging materials from the demolition. You won’t save much money from this but if you care about the environment it’s a no-brainer. To accurately access whether there is an environmental case for replacement, you’ll need to see a carbon lifecycle analyst.

The choice is yours...

The above sections have discussed some of the deciding factors, but it’s up to you to figure out which ones are most important to you and whether you should renovate or rebuild. For example, if cost and design freedom are your priorities, that points to a new build. If sustainability and convenience are more important to you, a renovation is the way to go.

Have you made the decision to renovate or rebuild? Let us know about your experience at @KoruArchitects.

Was this article helpful? Sign up to our newsletter for more useful blog posts about sustainable design, in your inbox every month. Or if you're looking for an architect for your project (whether you decide to renovate or rebuild) take a look at our services page.

01273 204065

Studio 221, 91 Western Road,
Brighton and Hove, BN1 2NW


Subscribe to our newsletter.

Get access to latest news and all the features by subscribing here.

© 2021 Koru Architects  |  Privacy & Cookies Policy

Designed by 22Group