Video /
Dec 12, 2019

5 Characteristics to Consider When Choosing an Architectural Material

Weighing physical characteristics, context, and cost among the most important factors

 

Choosing the right architectural material for the job can be overwhelming, so architect Eric Reinholdt, founder of 30x40 Design Workshop, revealed the top five characteristics he weighs before making a decision. 

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Professionals have a plethora of materials to choose from, such as wood, steel, concrete, and porcelain. The five categories Reinholdt says architects should base their choice on are the physical characteristics of a material, the context of the project and material, its experiential qualities, cost, and manufacturing concerns. Although he gives his suggestions as a list, he stresses that each project is different and the categories do not rank in any particular way. Instead, people should consider how these characteristics work together before finding the perfect material. 

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“Material selection requires you to be an observer and student of the built world,” Reinholdt says. “Study buildings you admire and note how the material qualities affect how you feel there. Choose a few simple materials and get to know them deeply. Concrete and wood are excellent places to start.” 

Watch the video to learn Reinholdt’s full process. 

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Transcript: 

Architecture can’t exist on a page: It must be built and transformed our drawings and tiny cardboard models into physical reality means choosing materials to represent abstract ideas. Now, I find this part of the design process so interesting because I really view it as a form of storytelling. By simply varying a building’s materials we can create something entirely different. Now, although this is part four of the course, I’ve actually been thinking about the architectural material palette for our case study project since the first time I visited the site. Now, I always pull together potential materials I want to use during the early design phases because, for me, they help determine the building’s form and they shape the narrative and experience I want the design to convey. Material decisions - for me – tend to arise from the design concept, strengthening and supporting it and the process requires making many choices, about form, about scale, about color and texture, about construction, water-tightness and durability, about installation and finishing, and of course cost.

Understanding the properties and uses of building materials is as much the duty of an architect as understanding good proportions or physics. So, let’s get into the five categories architects consider when selecting materials for our architecture. Every material will have characteristics present in each category, but will also have a more dominant place in one or another. In this way, the categories overlap and it’s ultimately up to the designer – the architect– to decide how to prioritize the criteria that matter most to the design.With each one I’ll present the principle then describe how our material selections were informed by it.

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The first, and most obvious are a material’s physical characteristics. This includes its weight, porosity, density, strength, acoustical properties, its resistance to weathering, its structural properties and this extends to how it will be supported or fastened and how it impacts the physical performance of a building. Then there’s the ever-important physical appearance or aesthetics of a material: color, texture, shape, how it patinas, is it glossy, or matte or smooth? And finally, the physical characteristics include maintenance concerns as well; is it easy or difficult to keep a material clean or in working order for example? Now, many architects quite naturally begin with the physical characteristics of a material. What are the aesthetic goals of the project?

For our project, I’ll start by referring back to the concept now we’ve been designing an encampment by the sea that sits at the edge of a forest and closely follows the topography. So, I’ve drawn from the building’s wooded context to begin choosing the material palette. To tie the architecture to the surrounding site and to defer to the landscape - the forest and the water - it was important to me that the building recede as much as possible.

I wanted the building to be discovered almost like a shadow in the woods. Now, as architects we have only a few physical elements to accomplish this: there’s the walls, which also include doors and windows, there’s columns or exposed structure, there are roof surfaces either flat or pitched, and then there’s horizontal surfaces – things like steps, decks and walkways. For the walls, I chose an exterior siding of dark stained cedar shingles because dark colors tend to recede. I initially preferred an even darker Shou-Sugi ban siding, but the cost and the hue were limiting factors for my client. So, we agreed on a dark matte green stain selected among many different hues as a balance between the bark and foliage of the conifer forest. Shingles are nice because they create a natural texture and shadow to the wall surface. So, you can already hopefully see how I’ve prioritized the appearance characteristics of the material as being more important than the other physical concerns.Now, that’s not to say I don’t care about porosity or density, but they’re secondary or maybe even tertiary.

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Wood will wet and dry quickly if I build it in such a way that there’s a ventilated rain-screen behind it. Cedar is naturally rot resistant and factory finishing the shingles provides a long finish warranty period so we’re also ticking the maintenance checkbox here too. If – as we’ll get to soon – cost were the most important I’d probably choose materials which wouldn’t require any finish. That approach, however, might not blend in to the forest as well. Along with the siding, the walls are comprised of windows and doors too. For these we’re using an aluminum clad window. Using metal clad windows limits maintenance over the long term, especially here on the coast. We could’ve chosen all wood windows and painted or stained them, but our priority here was to minimize maintenance on a particularly expensive to maintain building system. We chose black from among their standard color options for the frames because it adds punch to the openings, kind of like eye-liner and glass in exterior walls is perceived as black during the day so it contributes to this receding effect we were after. It also means that during the day the entire wall surface will be viewed as one unit, rather than calling attention to the window and door frames. 

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Hardware for these is all stainless steel so a light gray color mainly chosen for its resistance to corrosion. Trim at the roof, soffit and around the openings was designed to be as low profile as possible and all are stained to match the shingles. All concrete was left unfinished and exposed as we’re insulating to the interior face. Now, this is a concept called truth in material. For further reading about this idea be sure to check out the Arts and Crafts movement of the late 19th and early 20th century as well as the modern movement, both were exploring and developing the truth to material concept: using a material for its inherent physical properties and exposing it for its natural beauty rather than concealing it. Concrete has superior compressive strength but rather poor tensile strength so a truth in material approach would use concrete in locations of a structure subject to high compressive loads. This is why you see it used often in foundations. Steel, by contrast, is excellent in tension making it ideal for long beams which deflect under load and tensile forces.

Combining the two, we have reinforced concrete – concrete with embedded steel rebar - which marries the best properties of both materials into one. Now, there are certainly many more approaches to selecting materials, but this one in particular resonates with me personally as the most honest and forthright strategy. The site retaining walls were poured in place concrete with a board-formed finish. Here again, we’re recalling the forest environment, using the horizontal lines to reference the siding, to reach out into the landscape and the wood grain is an abstract nod to the trees of the forest. I also like that the board forming reveals the process of making - how concrete transforms from a plastic material when poured to a weather-resistant solid mass when cured.

The horizontal coursing matches the siding and the dull gray conforms to the muted palette

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of the building as well as the granite outcroppings and the gray of the nearby ocean. Let’s move on to the second category we use for material selection: context. Now, context can mean many different things. It can be a material’s physical context – like its exposure, will it be used inside or out? Will be exposed to water and sun, or to wind or corrosive or hazardous materials? Context can also refer to a material’s proximity to other materials or nearby structures that use a common architectural language or even a historical context, clay tile or brick is a good example. It can also mean a material’s cultural context, local building traditions or specific meanings. And then there’s also the functional context of a material, for example it would be difficult to justify constructing a prison entirely out of glass, right?

Our project has many different contextual meanings to draw from. I mentioned the forest which has informed our decision to choose a dark siding, but our materials also have a variety of interior and exterior exposures and a precise location near the salt water. Equally, our interior materials will be adjacent and experienced in conjunction with the exterior materials. So, lots to talk about here. Context is intimately linked to the concept of contrast and it’s one the most important things to understand with respect to choosing materials. It’s what distinguishes one thing from another and we use it to make sense of our world. Gray concrete feels cooler and wood feels warmer when these materials are next to each other. Similarly, textured surfaces appear more textured when placed near smooth surfaces. We can use this in our architecture to emphasize our ideas. Hard, soft, warm, cool, light, dark. Heavy, slight. Here we’re using both context and contrast to great effect when we move to the interior material selections. The rough bark of the exterior siding gives way to a smoother, warmer toned interior. For the floors in the main living spaces I selected a local red birch in a five-inch wide plank. This sets a warm plinth which grounds the space. If the exterior is the bark of the tree, the interior contrasts that by acting like the heartwood, warm and welcoming. At night, the dark shadow of the building virtually disappears into the forest and the warm wood is like a lantern or a tent in the forest lit up like a beacon.

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The entry areas and connectors will receive a gray porcelain tile – a highly durable stone alternative and a result of its functional context hosting soiled foot traffic. We had hoped to use natural stone or poured concrete, but the tones of the local stone and concrete mix didn’t align with our client’s taste. So, this was a compromise. We opted for the porcelain for its low relative cost, its durability and its low environmental impact as its made primarily from recycled material. The cleft finish is another play in contrast against the nearby satin of the oiled wood floor. To help the view to take prominence inside, we’re painting the window frames black rather than matching the adjacent wall surface. The idea is again to downplay the window frames, to dissolve them. Walls and ceilings are primarily painted gypsum wallboard and this too was done to downplay their presence. Inside, we wanted the spaces to be about the warm floors and the views to the site.

Alright the next category is a material’s experiential qualities. Materials may seem hard or soft based on our perception. For example metals are often perceived as hard even when their physical properties might suggest otherwise. Aluminum is a soft metal, but it’s often perceived as hard. This is because of personal bias or associations with certain materials. Now, these emotional connections shouldn’t be underestimated. I once had a client who disliked my suggestion for a metal roof as she had grown up living beneath a metal roof and associated that with a difficult time in her life – a time she’d rather forget. In part, the experiential qualities informed our roof material choice. Standing seam metal has this crisp, taut look that reminds me of a Maine woods camp.So here we’re relying on what the material connotes or signifies. But the roof is a great example of a choice where many factors influenced our decision. I wanted to maintain the monochromatic exterior color palette and so I chose a zinc-colored painted aluminum to coordinate with the wall color. We could’ve selected zinc or a lead-coated copper - truth in material - but both were cost prohibitive and the rainwater run-off from zinc reacts with cedar in unpredictable ways. Metal balances a streamlined installation cost – because big panels go up quickly, and a low life-cycle maintenance cost. Another consideration here on the coast, we have to be really careful about which metals we use in the corrosive salt air. For the roof, I chose PAC-Clad’s painted aluminum metal roofing system which carries a 30-year coastal warranty. Now, all these factors play into the final decision, but one is always more dominant than another.

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Certainly, the experiential qualities of materials and a building’s interior design are codependent. The money we saved by using gypsum wallboard everywhere, we allocated to purchasing machined structural tie rods and clevises. These are all exposed and fabricated from stainless steel and they clearly express the tensile forces of the structure in the main living space. Where the outer walls want to spread apart under the roof load, and the tie rods hold them together in tension allowing us to vault the ceiling and increase the volume of the main living space. Importantly, these rods convey both camping and nautical experiential cues – cordage and rigging. Now, we’ll get into the design of the kitchen and the baths in a future video, but briefly in the bathing spaces, the floors and shower walls all receive the same dark gray tile we’re using at the entry and connectors we’re mixing up the texture of the floor with a pebble tile at the bathtub and shower rooms.The pebbles help with grip under foot and they reference beach stones. The fixtures in the baths are gloss white and polished chrome which contrast the rough textured floors and then we finish out the bathing spaces with etched glass shower wall dividers which will act as sort of these bright luminous planes in what are relatively dark bathing spaces.

Moving on, we come to costs. And here we include, not only the material costs, but acquisition costs, maintenance, shipping, and installation costs. Often new cutting edge materials will increase labor costs due to unfamiliar installation Processes. All materials have a cost and if you have a lot of area dedicated to one material like our shingled walls for example you have to be careful not to specify an expensive material to keep within the project budget. Or at least be cognizant of it. Shingles have been used on the coast of Maine for a long time because they’re durable, rot resistant readily available and fairly inexpensive. Selecting local materials is always my preference when possible because it’s a more environmentally friendly choice. It also maximizes the local labor force’s experience installing them. Even though the material is economical, labor can add up quickly as they’re installed one at a time. The shingle coursing I initially specified was four inches - meaning every three courses would equal one vertical foot, which aligned nicely with the window and door openings. To me, this presented more of a textured face but it also required twenty percent more shingles per square foot of wall area and that quickly became a cost concern. This additional cost of material and labor was significant and so we compromised to a more standard five-inch coursing. Now, this is common practice in design, we propose ideas and then test them against a host of factors. We revise and revisit as we receive additional information, in this case cost information. Was a twenty percent increase in the cost of the siding justified? Was the added effect worth it? In the end, our answer was no, but perhaps for a much smaller structure it may have been.

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Yes. Cost implications and material selections are one of the easiest things to weigh during the design process. It’s one reason they’re the target for cost-savings efforts along the way. But, typically, the biggest driver of cost is the overall square footage of the project, not material cost. Even so, we’re careful here to limit the more luxurious materials – like soapstone – to limited areas. And these are areas that we’ll be interacting with on a daily basis, like the kitchen counters. And the fifth consideration here is related to manufacturing. Here we’re talking about installation, acquisition, assembly or finishing. Now, this may also apply to environmental impacts too things like how resource intensive it is to manufacture, to mine, or procure. Life spans of materials fit in this category too. The decking choice is a good example of something we struggled with with respect to sourcing and environmental impact. 

Now, I love using the local cedar here for decks, it’s really soft under foot and it weathers to a nice, light silvery gray which would also mimic the horizontal plane of the nearby water nicely, but its softness is a real liability, it affects durability. It’s significantly less expensive than a tropical hardwood like Ipe, but doing a quick life-cycle cost analysis, we discovered we’d have to replace it more often than a harder, longer lasting material like Ipe. The Ipe is more expensive to acquire and install, but it will last much longer and has the same visual appearance characteristics as the cedar, weathering to a nice silvery grey. In the end it was cheaper. 

We sourced ours from a managed forest to diminish the environmental impact of it as well. So, in this case the long-term durability trumped everything else. So, those are five general considerations which will inform your material selection for your architecture. Remember, each of these material considerations can be thought of democratically; that is, none is necessarily more or less important than another. Your design should begin to suggest what materials best represent your ideas. And it can be precious few. You want to study the work of architects like Tadao Ando, Louis Kahn, Peter Zumthor, LeCorbusier and Aalto – and witness the depth of knowledge and skill they deployed using a relatively limited set of building materials: wood, concrete, glass, and brick. You can say quite a lot using a very spare palette of materials. Now, the take-away is that the material selections were a result of intentionally considering all aspects of the experience we wanted to create for our client as well as the necessity of building something durable and meaningful here in an extreme coastal environment. It has to look good and tell the right story. It has to comfort and shelter, reduce and minimize our impact on the site and recreate - in an abstract way - the quiet of the forest in the new place we’ve created. It’s a tall order, but by following a process which prioritizes the most important characteristics for each part of the architecture you can find a methodology for choosing wisely. Material selection requires you to be an observer and student of the built world. Study buildings you admire and note how the material qualities effect how you feel there.Now, if I’ve helped you at all with this video I’d so appreciate a thumbs up below, it helps me to grow the channel and to know I’m making the kinds of videos you’re interested in watching. Be sure to hit the notification bell to be notified whenever I upload a new video.

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Cheers!

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