Materials

    A luxury, freestanding bath with half marble stone wall surface covered

    Part 81: 6 pitfalls to avoid when specifying stone

     1000 690 Hamish Kilburn
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    Part 81: 6 pitfalls to avoid when specifying stone

    In part two of Hotel Designs’ exclusive editorial series with Stone Federation, we share some of the common mishaps designers and architects encounter when specifying stone… 

    A luxury, freestanding bath with half marble stone wall surface covered

    Natural stone is a truly versatile material with a rich history of being used to create memorable, durable and sustainable hotels, both inside and out. It is a material that delivers uniqueness by the bucket load as no two pieces of stone are ever exactly the same, thus enabling hotel designers to create truly one-of-a-kind spaces.

    As with any material, the necessary know-how around selection, design and maintenance is key to delivering a successful project. One of the advantages of using natural stone is that it is a material that has been used in hotels for centuries and is supported by a vast wealth of technical research as well as British & European Standards.

    The following pointers are designed to be steps on the journey to you delivering a beautiful, durable and sustainable natural stone project.

    1) Specifying the wrong type of stone

    There is a commonly used adage in the natural stone industry that there is no such thing as a bad stone, just a badly used one, and this holds true project after project. Natural stone is, as the name suggests, a natural material and, just like any other natural product, it will react and respond better in certain situations and less well in others. For example, some stones will work perfectly well as wall linings in lobbies or other dry areas, but would prove to be unsuitable if used in wet areas like shower enclosures.

    Engaging with a stone consultant early in the project, pulling on their material expertise, and matching your design vision with the right materials for that application, will help ensure that you specify the correct stone for that specific project.

    Spa – Four Seasons Hotel London at Ten Trinity Square – Arch

    Image credit: Four Seasons Hotel London at Ten Trinity Square

    2) Forgetting it’s a natural product

    This might seem obvious, but with the ever-increasing number of man-made, stone-effect products being pushed into the market, it could be easy to forget that natural stone is just that, a naturally occurring material that has not been ground up, mixed with resins and other ingredients and coloured with dyes.

    The unique and natural veining, tones and textures found in stone are what make it such a special material. No two blocks of stone will ever be exactly alike, and embracing this as opposed to specifying out any variation or difference in tone and vein pattern is the best way to work with, and not against the natural dynamic of stone. It is vitally important that the stone is viewed under appropriate lighting conditions that imitate the in-service conditions, and that a full range of the stone’s visual characteristics are captured in a range report used as part of the stone supply contract.

    Make every specification decision about natural stone through the lens of its natural characteristics, embrace its uniqueness and you will end up with a project that takes full advantage of the organic nature of the material.

    3) Trying to move away from movement joints

    Like all building materials, natural stone will be impacted by changes in environmental conditions (heat, impact and traffic), which is why it’s important to provide stress-relieving movement joints.

    When designing a natural stone floor, there a several questions that will help deliver a durable scheme and avoid failures in the floor.

    The first step is to ascertain whether you need a movement joint.  Simply put, where the distance between restraining surfaces including perimeter walls exceeds two metres, a perimeter movement joint must be installed. Intermediate movement joints are required where the distance exceeds 10 metres. With underfloor heating, the natural stone flooring should be divided into bays of up to 40 metres squared, with a maximum bay length of eight metres.

    It’s also important to consider whether the floor will be subject to light or heavy loading, and whether there’ll be underfloor heating. If the floor will be exposed to low loading, or in a low traffic and impact area, a sealant would provide a suitable movement joint. If the floor is in a higher traffic environment a pre-formed movement joint, typically comprising metal side plates with a flexible synthetic rubber core may be more suitable. If there is an underfloor heating system, the pipes or cables should be located to ensure that the system is contained within the pattern of the movement joints.

    Hotel interior designers should also take drying shrinkage into account because stone, like all finishing materials, reflects movements arising from supporting substrates. In the early period of a floor’s life cycle, movement occurs primarily from the drying shrinkage of the slab and screed. As a rule of thumb, a typical 10 metre span slab will experience drying shrinkage of three millimetres irrespective of design, depth or amount of reinforcement used.

    Close-up of stone on wall

    Image credit: Stone Federation

    4) Forgetting that slip resistance can affect material appearance

    When discussing slip resistance within hotel design, it’s important to have a basic understanding of a few of the fundamental points relating to the equipment used to establish slip resistance and the means of assessment of results generated.

    Most of the guidance and specified in-service performance criteria will quote values in Slip Resistance Value (SRV) or Pendulum Test Value (PTV) – these are the same.

    A material’s slip resistance is determined by several factors. The choice of stone, choice of finish and choice of sealant or impregnator will all have an effect on the slip resistance properties of the finished floor.

    When deciding on which material to specify it’s important to understand how the material’s appearance might change when the texture that enables that material to achieve the required slip resistance rating is applied. For example, a polished marble will look very different to a honed marble, as the polish will reflect light whereas a honed finish will absorb it, making the colours of the stone appear more muted.  Considering these factors early in the project will help avoid challenges further down the line.

    “This comes back to the point about there being no such thing as a bad stone, just a badly used one.”

    5) Aftercare treated as an afterthought

    Natural stone, like any other material, requires maintenance to keep it looking and performing at its best. Understanding the geology of the material specified, its porosity and absorption is important as different stone types will require differing levels of care and maintenance. It’s also worth noting that heavily trafficked areas will require more maintenance than those that are seldom used.

    One of the most common pitfalls made in the maintenance of natural stone is the use of incorrect products that damage the material. The use of acidic products should be avoided as they can remove any surface sealant or in extreme cases damage stone. It is best to use carefully considered ‘proprietary’ stone cleaning products that will typically be of neutral pH or mildly alkaline.

    Working with your stone supplier to develop an ongoing maintenance plan before project completion will help manage client expectations from the outset.

    A large, luxurious arrival experience inside the plush Adare Manor

    Image credit: Adare Manor

    6) Unexpected interactions

    Considering the environment in which the stone will be used is key to avoiding one of the most common pitfalls in the use of stone in hotels: staining or marking caused by products like wine, make-up or other acidic substances or staining caused by a repeatedly wetted stone without the required drainage. This comes back to the point about there being no such thing as a bad stone, just a badly used one.

    Taking into account the substances that the stone will interact with will help you specify the right stone for that environment.

    Natural stone is a truly unique material providing hotel designers with a whole host of unique tones and textures and the ability to deliver sustainable, long-lasting projects. By considering the points raised above, you can help avoid some of the most common pitfalls. Stone Federation also always recommends working with a stone consultant as early in the project as possible, and make sure that you choose a Stone Federation company at each stage of the process to ensure that you are working with the best companies and materials.

    > Since you’re here, why not read the first article in this series about ‘measuring sustainability in surface design‘, or Stone Federation’s collaboration with Squire & Partners, Stone Tapestry?

    Main image credit: The Wellesley Knightsbridge

    Spa Pool – Four Seasons Hotel London at Ten Trinity Square – Architect Joseph Caspari with Mio Shibuya

    Part 76: how to measure sustainability in surface design

     1024 640 Hamish Kilburn
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    Part 76: how to measure sustainability in surface design

    As Hotel Designs rolls into its largest feature around sustainability in the publication’s history, we asked Stone Federation to share its insight on sustainable surfaces. In part one of this three-part series, we learn how to measure conscious sourcing when it comes to surface design…

    Spa Pool – Four Seasons Hotel London at Ten Trinity Square – Architect Joseph Caspari with Mio Shibuya

    In this ‘material world‘, there is no avoiding it. Sustainability has never been as high on the agenda as it is now – and the delivery of sustainable interior projects is a must.

    The hotel sector, perhaps more than others, has an even greater drive to deliver as customers are looking to the items they consume and companies with whom they spend their money to be proving their own sustainability credentials. In an industry where everyone is looking for the factor of difference, their unique selling point, providing customers with truly sustainable spaces isn’t just good for the planet, but can also make a lot of business sense.

    Statuario Book-Matched Bathroom marble

    Image credit: Stone Federation

    It is no longer just enough to use carbon offsetting or sponsoring the planting of trees as a low-commitment route to demonstrating a sustainable approach to business. Companies must prove they understand the concepts of true sustainability and design their hotel in accordance with these.

    Before answering any question about sustainability, defining the term is important as there has been an unfortunate amount of greenwashing within the design sector.

    From Stone Federation’s viewpoint, when we talk about sustainability, we’re assessing the whole-life cycle of a project, which includes the raw material extraction, production, distribution, use and end of life. From our perspective, the fewer processes required to get from raw material to finished product the better for the environment and the more sustainable the material.

    Dramatic entrance into the lobby at Adare Manor

    Image caption: Dramatic entrance into the lobby at Adare Manor. | Image credit: Adare Manor

    For natural stone, the process is relatively simple: stone is quarried or mined from the ground, cut into slabs or tiles, transported to site and will often last for decades, and in many cases, centuries. Thanks to its durability, there is also the potential for the creative reuse of many stones delivering a truly circular project.

    What’s more, the quarries and mines themselves have a fantastic track record of reuse or repurposing. You only need to look at Honister Slate Mine in Cumbria which has been turned into a zip wire experience or the Tout Quarry on the island of Portland which has been restored as a sculpture park and nature reserve to see just how circular and sustainable the natural stone extraction process is.

    Albion Stone Quarry

    Image caption: Albion Stone Quarry. | Image credit: Stone Federation

    While some ‘stone alternative’ or ‘stone effect’ products require intense heat and pressure to bond the resins, pigments and other ingredients, natural stone comes out of the ground ready to be cut, finished and fixed.  While many of these alternative products are marketed as a ‘stone-effect’ option, they cannot emulate the natural beauty or sustainability credentials of natural stone. Natural stone is, by definition, a natural product, formed in the Earth over many millions of years, extracted, cut to size and transported to site without excessive human intervention and invention.

    So, in the first instance, measuring sustainability in surface design starts with assessing the number of processes that have gone into the creation of the materials being used.

    It’s not just the extraction process that makes natural stone such a sustainable choice for hotel designers, the durability of stone is also part of what gives it such impressive sustainability credentials.

    This dynamic of durability is another metric for assessing sustainability in surface design – how long will this material last?

    Close-up of stone on wall

    Image credit: Stone Federation

    So many of our nation’s historic hotels, churches and public buildings have natural stone floors that are hundreds of years old and still performing well. It is very rare to find the same with some of stone’s competitor materials. Much of this strength is thanks to the millions of years of compressive geological processes that go into the natural formation of stone. For a material that takes millions of years to form, providing a 100-year project lifespan is unsurprisingly commonplace for many stones.

    Another way to assess sustainability in surface design is to look at a material’s ability to be reused or recycled should there be renovations or change of use. Natural stone, thanks to its durability, can be reclaimed, reused or even repurposed as furniture or pieces of art.

    It’s not just these general principles of assessing extraction processes, material life span and reuse that help in measuring sustainability in surface design, there are also a number of detailed studies that have provided hotel designers with the facts to inform their material choices.

    A marble fireplace

    Image credit: Stone Federation

    When comparing natural stone with large-format ceramics, terrazzo, and other flooring products, stone’s global warming potential was found to be significantly lower. The GWP figures showed that, for example, large-format ceramic tiles have a 74 per cent higher Global Warming Potential than natural stone and terrazzo are 27 per cent higher.

    There are many other examples of studies that have demonstrated the sustainability credentials of natural stone. Moving slightly away from interiors, but still on the topic of sustainability there was also a project in London, 15 Clerkenwell Close, where the use of load-bearing natural stone instead of a concrete and steel structure reduced the whole-life carbon footprint of the building by 95 per cent and the cost by 75 per cent.

    Finally, the Green Guide to Specification, which is part of BREEAM, sets out an A+ to E ranking system for the environmental performance of materials. In a case study project by the BRE, almost half of the natural stone-related components achieved either A+ or A and the majority of the remainder scored a C or above.

    In summary, measuring sustainability in surface design boils down to first defining what makes a product sustainable and then comparing all materials against those same criteria. A low-impact material extraction or creation process, longevity of the material and ability to reuse, reclaim or recycle are all good first indicators, but when placed alongside the facts of comparative studies, it’s hard to ignore the fact that natural stone might just be the hotel designer’s ideal sustainable material.

    > Since you’re here, why not read about Stone Federation’s collaboration with Squire & Partners, Stone Tapestry?

    Main image caption: The pool in the spa at Four Seasons Hotel London at Ten Trinity Square, designed by architect Joseph Caspari with Mio Shibuya. | Image credit: Four Seasons