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Natural Roofs

Let's face it — every house needs a roof. Especially in the northeast! And while leaks in the wall may lead to a bit of heat loss, leaks in the roof are an entirely different story — the margin of error is slim in the world of roofing. And as in every other part of the house, there are a range of strategies and materials available to the builder. To find the natural roof systems available to us in cold climates, we look again to the pre-industrial builders of yesterday, as well as to the work of their contemporary counterparts.

Venting the Roof
It is not uncommon throughout cold and snowy places to see the effects of 'ice damming' — deadly stalactites of ice hanging from the gutters, threatening to impale unwary passers-by, and causing roof leaking due to water back-up on the roof. What's happening here is that warm air from the building rises and heats the underside of the roof. This in turns melts the bottom of the snow pack on top of the roof, and the resulting water runs along the roof to the eve, where upon reaching the unheated edge of the roof, refreezes into ice, dripping into massive icicles and blocking the way for the water behind it to run off, which in turn backs up under shingles and flashing. There are two ways of avoiding this: venting your roof, or having a very well-insulated roof. In the latter, one relies on the quality of insulation and air barrier in the roof system to keep any warm air from the house from reaching the roof. This has a benefit of allowing the roof to retain snow (depending on roof type and pitch), which is itself an insulator. An example of this are 'panel roofs', which are thick foam-insulated roofing panels crane-lifted onto roof structures (often exposed timber framed roofs). The vented roof refers to a channel of cold, atmospheric air ducted underneath the roofing or sheathing and vented at the eves and gable ends or ridge; this ensures that any warm air that does reach the underside of the roof is vented away, keeping the roof cold. Hence the colloquial name for such as system: the 'cold roof'. Such roofs are often considered to be the most reliable for avoiding ice damming. Different roofs will call for different strategies, and it should be recognized that one is not inherently better than the other; rather, one is better suited to certain roof and building designs than the other, and both should be considered when making a decision as to what type of roof is right for the building.
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Slate roofs are heralded in this region for their beauty, durability (lasting hundreds of years or longer with general maintenance), quality, fire resistance, and tradition. Essentially stone shingles, slates are thin slabs of stone that are nailed in place in an overlapping, shingle-style approach. Slate is still produced regionally today, with many slate quarries operating throughout New York and New England, as well as a small but vibrant industry of tradespeople involved in both restoration and new installation. Being stone, slate is very heavy and structural considerations for the increased dead load must be considered. From an aesthetic vantage, different veins in different parts of the world will produce different colors or patterns, and sourcing local material will literally brand your structure with the colors of that land. Additionally, multiple colored slates can be used to create patterns simple or intricate.
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Wood Shake
Traditionally cedar, but occasionally hardwood, shakes (another word for shingles) have been used in this timber-rich environment for hundreds of years. Historically, squared blocks of cedar heartwood (the dense center of the tree) were rived (split) into blanks, which were then 'dressed' to be smooth and tight-fitting, and laid up on the roof surface, again following a shingle pattern. When wet, the wood would expand and gaps and cracks would be filled with the swollen wood; sometimes multiple layers of thinner shakes would be installed. Today, one can find manufactured wood shakes, although careful attention to quality should be paid, as well as to fire prevention for a wooden roof.
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Nothing defines Mediterranean architecture like curved clay-tiled roofs. Either S-shaped, cupped, or alternating convex and concave, earthen tiles — porcelain or ceramic — have proven their merit. Earthen tiled roofs can also be found vernacularly in Latin America and Japan. While by no means a vernacular style in this part of the world — in relation to the lack of vernacular earthen construction — there is still a valid argument to be made for their use, particularly if the feedstock and manufacturing can be sourced regionally to avoid the impact of transportation. Similar structural considerations should be taken as per slate, given their weight.
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Common throughout climates as far ranging as northern Europe and the equatorial tropics, thatch or grass roofs have been sheltering structures for thousands of years. There are two distinct categories, tropical and temperate thatch. Being temperate in climate, we look to this tradition, which generally involves the use of water reeds or grasses — most commonly phragmites — or if unavailable, rye or wheat straw. The fibers are bundled into sheaves, which are then tied and/or pegged to the roof framing; successive layers of thatch are overlapped from the eve to the peak, where a thatch cap sits atop the gable. Thatching is a craft, and one that has been — and some would argue currently is — on the verge of being lost. A well-done thatched roof will last for years — 50 or more, with only the cap needing replacement every 10-15 years — and do a fine job of both preventing moisture entry and aiding in insulating the structure. Again, fire is a concern here, as is finding the abundance of both material and human resources; if practical, however, a thatched roof rates high marks for both aesthetics, performance, and ecological sensibility.
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Living or 'Green'
More and more common throughout rural and urban areas alike are living, or 'green', roofs, in which a sod layer is seeded or planted with a carefully selected palette of plants and installed at a low or flat pitch over a water-impervious membrane. These roofs, found on everything from country studios to city apartment complexes, are designed to capture and harness the water that falls upon them, using it to encourage plant growth and be respirated slowly back out into the atmosphere. These roofs are of particular value in urban environments, where they serve to return greenspace to the concrete landscape — aiding in both human and non-human quality of life benefits, help to address stormwater drainage issues by slowing and reducing the amount of water passed off the roof, and help to address the 'heat island' phenomena of increased temperatures in concrete-dominated environments. That said, green roofs are also appropriate in rural contexts, particularly in those where an attempt to integrate into the natural landscape is desired, as in subterranean (underground) or low-profile designs. It should be noted that in many commercial applications a significant amount of synthetic materials are often employed for root barriers, moisture barriers, or drainage mats. Again, structural provisions will need to be made for the increased weight of the roof, although temperature moderation benefits will be reaped.
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Modern Roofs
While not necessarily 'natural', there are many modern technologies that have lent themselves well to being on the roof. Even good old fashioned 'tin' (now usually steel or aluminum) roofs are made from recycled materials and are themselves readily recyclable; beyond that, there are a plethora of new products out there, and more coming online all the time. As mentioned above, there are many living roof systems that are commercially available, some more appropriate for smaller-scale residential construction than others. Many single-source or composite recycled materials, such as recycled plastic, rubber, or cement-stabilized reclaimed wood fiber, are being used to create roofing shingles to replace the more environmentally damaging traditional asphalt shingle. And multiple styles of BIPV (Building-Integrated Photovoltaic) roofs, from peel-and-stick products for standing-seam metal roofs to 'solar shingles', are currently available throughout the northeast. It is safe to say that in the years to come, our options will only grow.
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