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What is the Best Roofing Material Available?

A Comparison of Roofing Materials

 

 

 

 

 

 

 

 

There are many products available for roofing a house, making it a difficult choice for the homeowner.

Some considerations are material costs, installation expenses, weight of the materials and requirement for additional support structures,

environmental impact, longevity and aesthetics.

 

For each consumer the importance of each of the many variables has different significance, for example, for one the high cost of slate materials

and installation makes it so it is not even a candidate for their roof.  For another, the longevity of slate is the most important factor, making it very

appealing, overriding all other considerations. For yet another, who is not concerned with cost, perhaps environmental factors in mining slate eliminates it.

 

 

 

There really is no material which is best suited to every person and situation, what one person finds is best for their house simply won’t work for another. 

For example, a person with a very limited budget wanting a cheap material for their high slope roof, just to get through a year or two until they move to a

different residence, will likely decide to use the lightest asphalt shingle available, with easy installation, low cost, but also a very short life span, and install

over the existing roof.

 

Another could be in the same situation, but with a low slope where asphalt shingles will not work, obviously they can’t use shingles unless special

methods of installation are used.

 

For my part I want to consider all factors equally, not giving undue consideration to one or another factor due to my own preferences, but selecting a

product that performs well in all regards, presenting the information so the buyer can make an informed decision which will lead them to purchase the

best material for their individual needs.   

 

 

 

 

 

First, an overview of the materials and their properties.

 

Asphalt Shingles: composed of an inner core of fiberglass or cellulose, coated with asphalt on both sides and topped with a mineral aggregate. Asphalt shingles vary in weight and durability depending on the thickness of the shingle, from 12 to 40 years. They can be treated with fire-retardants. Asphalt shingles are the most common roofing material in North America.  Application is very easy, but requires a high slope.  This can be one of the cheapest and easiest materials, but also one of the least durable, and they use nonrenewable materials, petroleum distillates, mineral aggregates and fiberglass, with the exception of one component in some shingles, cellulose.  They are available in a variety of styles and colors, with different aggregates which can provide differing qualities in longevity and UV protection.

 

 

 Asphalt Torch–On: Bituminous membrane roll roofing is a continuous sheet of asphalt shingle material rolled into a cylinder. The major difference between roll roofing and asphalt shingles is that roll roofing is much thinner and lighter, due to the requirement for it to be flexible, so it does not last as long.  It can be used on lower slopes than shingles, and can very quickly cover a large area.  The major drawbacks are the short life expectancy, the environmental concerns over petroleum distillates and mining, and aesthetics, as rolls are not as versatile in allowing designs and texture.  Application with a propane torch on the roof also poses a fire hazard.  This is likely the cheapest material, with the fastest installation, but is the least durable of all roofing materials.

 

 

Gravel and Tar: This is similar to an asphalt shingle or roll, but each component is installed separately and in more robust dimensions.  It consists of alternating layers of felt and tar, with a top layer of mineral aggregate. This type of roof is most commonly used on commercial buildings.  This can be a very durable material, with low maintenance costs.  Some concerns are the support structures, which must be very robust.  Other concerns are the environmental impact of petroleum and gravel mining, the need for skilled installation.  Gravel can be blown off by wind exposing the underlying structures to UV damage.  Built up roofs can not be applied on slopes of more than 3:12 pitch.  Summer heat can make the tar and aggregate run and sag, exposing upper sections of the roof.  Due to low slope this is not recommended for areas with heavy snow or rain. Another concern with low slope is the accumulation of organic debris, the roots of resultant plant growth can penetrate the membrane.

 

 

  

 Plastic Membrane: Also known as burnt-on roofing because it is heat sealed, this type of roofing resembles a large, shrink-wrap sheet covering the roof frame and underlay. The membrane itself is made from a variety of materials, ranging from rubber to fiberglass reinforced plastic or thermoplastic. Like built-up roofing, membrane roofing is fairly durable and is more common in commercial structures. Some common materials for membrane construction are EPDM (ethylene-propylene-diene-terpolymer membrane), CPE (chloro-polyethylene) and CSPE (chloro-sulfonated-polyethylene).  It can be very light weight, can be used on very low slopes.  Some materials are very fragile, all are non-renewable resources, petroleum distillates and mined minerals.  There are few options in appearance,  and it has poor insulating properties.

 

 

 

Wood: usually in two forms: shakes and shingles. Shingles are smooth and uniform while shakes can have a rough, uneven texture, requiring an additional membrane between each course.  Previously green wood was used, it is now available kiln dried, treated with fire retardants, primer, paints and stains, also in a variety of textures and profiles. There are many woods in use; each has unique properties in aesthetics and durability.  Pine and White Cedar are the least durable at 15 to 30 years, Yellow Cedar at 50-75 years, and Red Cedar which can last 100+ years.  Wood is light weight, has good insulating properties, good wind and impact resistance, easy installation and is the only truly renewable roofing product.  The drawbacks for wood is the requirement for a high slope, high cost compared to asphalt and short life of inferior species or poorly manufactured products. Clay and cement have more versatility in 3D forms.  It is the cheapest, lightest and easiest to install of the materials which could be considered long lasting. 

 

 

 

 Cement Tile: Cementitious roof tiles are made from steam-cured cellulose fiber-reinforced portland cement or concrete. Cementitious roofing tiles are very durable, resisting weathering, insects, fire, and fungus. Their weight also helps them to resist wind uplift, but requires robust support structures to handle the weight.  Cement shingles require skilled installation.  Failures usually occur due to growth lifting the shingles, failure of the fasteners or impact shattering the shingles, which can be very brittle.  they have poor insulation characteristics, but fair sound insulation.

 

 

 

 

 

 

Clay Roofing Clay tile, made out of kiln-fired clay, is one of the oldest and most durable roofing materials. It is extremely weather-resistant, fire-proof and insect-proof. Clay tiles usually require structurally strong roof decks and are fastened with a variety of clips and fasteners. Similar to cement tiles, failure usually consists of failure of the fasteners or, lifting of the tiles or impact.  Installation should be performed by skilled workers.

 

 

 

 

 

 

 Steel Roofing: Metal roofing takes many forms, including aluminum, copper and steel. It can come unpainted or factory finished with various coating systems. Steel panels have been traditionally used on agricultural and utility buildings, but they can be found frequently on houses and light commercial structures too. Like cement and clay tiles, metal roofing is durable and insect and mold resistant.  It can be very light weight and durable.  Like many other materials the heavier it is the more durable it will be, and more expensive.  The major drawback is it has very poor insulation properties for sound, cold and heat.  The material detrification consists of rusting, which can be abrogated by zinc or aluminum coatings, adding to cost, and the corrosion or failure of fasteners.

 

 

 

 

 

Slate Roofing Slate tile, like clay tile, has been in use for millennia. Properly installed, a slate roof has remarkable durability, and it requires little maintenance (used slate is available in some areas). When a slate roof fails, it is usually the fasteners or the flashing that are defective, and not the slates themselves.  It is very expensive for the materials, also installation is very expensive and requires highly skilled workers with specialized equipment.  It is recyclable, but is not a renewable resource. 

 

 

 

 

Comparison of Costs and Attributes for Roofing Materials:

In this comparison I have highlighted specifications for criteria where the material performs well against the competition.  The number of good characteristics is added in the last column, giving the material a score against other materials, the highest score is the best all-round performer. 

 

Material	Material ($/100 ft2)	Installation ($/100 ft2)	Life Span (years)	Fire Rating	Weight (lbs/100 ft2)	Renewable	Acoustic	Thermal	Score
Asphalt Shingles	30-100	70-125	12-40	A-C	225-385	No	Poor	Poor	5
Plastic (membrane)	Varies	Varies	10-12+	A-C	150-250	No	Poor	Poor	3
Gravel and Tar	N/A	N/A	10-15	B	250-400	No	Good	Fair	2
Wood	150-300	100-160	15-75+	A-C	175-400	Yes	Good	Good	8
Cement or Clay Tiles	125-500+	100-300	20-100+	A	375-1100	No	Fair	Fair	2
Metal	35-350	35-400	15-40+	A	50-270	No	Poor	Poor	5
Slate	350-800	250-450	30-100+	A	500-1000	No	Good	Poor	3

 

 

 

A specialized comparison follows, estimating the cost for material and installation amortized over the life expectancy of the materials.

 

 

 

 

There are several factors common to all roofing materials, one of which is the need to keep the roof clear of organic debris.  Leaves and needles from surrounding trees left on the roof will eventually become nutrients for plant growth on the roof.  The roots of this growth can penetrate most membranes or roofing materials, even those that seem impervious are damaged as it grows in between tiles of slate, ceramic clay or shingles, separating them and eventually leading to the failure of the roof. Even the most durable materials, like built up tar and gravel or slate roofs can be damaged by lifting slate tiles, or roots penetrating the bituminous membrane of a tar and gravel roof.

  

To get the full life expectancy of any roofing material the installation and maintenance procedures must be known and followed.

 

 Overhanging branches pose another hazard besides leaves and debris, through direct contact they can gradually wear a hole in a roof, as they move back and forth even in light winds.

There is also the risk of sudden catastrophic failure damage from large falling wood debris.  Falling branches can easily break many of the more brittle materials, like clay, cement and even lighter slate products.  Wood and asphalt are more durable in this circumstance.

 

 

 

 

The Green Roof

This requires special consideration because it is the latest fad, and if you don’t have one you’re like a cave man or something.

This kind of roof would seem to be the choice for environmentalists, it has great insulation factor for both heat and cold, excellent acoustic properties, greatly reduces runoff and is of benefit to the environment as it actually produces O2 and reduces CO2, while filtering runoff water.  But it isn’t all it’s raved to be. 

 

 The cost for the environment, and the pocketbook, is probably greater than any other material!  What?  That’s right, because not only is it the heaviest type of roof, requiring the most support structure and hence a resource hog, it also requires a completely sealed membrane of one of the other roofing materials (which it is trying to replace because they are unfriendly to the environment), so it isn’t replacing them, but using all the same material, a complete roof with another green roof on top of it, plus extra resources for support structures.

 

You basically have to build two roofs, the environmentally challenged asphalt PVC or EDPT membrane, spray on polyurethane or fiberglass reinforced membrane, plus all the drawbacks that these have (intolerant of shifting, constant moisture, traffic, roots, etc…), and then put the green roof on top of that.

 

Plus, unless you have a herd of deer trimming the grass, you’re going to have to maintain it, hopefully with a manual mower and not a gas powered one. Right, like that is going to happen, they don’t even make them anymore.

 

Anyways, if people want to ignore this common sense, there are several materials used to build the sub-structure, the membrane roof which must be used under the green roof.

As with all roofing materials, each has it's benefits and drawbacks.

 

Type/Thickness	Durability	Watertightness	Tensile Strength	Root Resistance	Environmental Impact	Comments
Asphalt (Bituminous) Membranes Sheet or Liquid-applied, Seamed	20~60 Years	Excellent	Excellent	Poor	Fair	Long durable service life, high tensile strength and superior watertightness.  No resistance to roots, Root Guard must be added.
Thermoplastic Membranes PVC, TPO, Single-ply, Sheet-applied, Seamed	10~20 Years	Fair	Good	Good	Fair	Good wear resistance, often used on roofs with foot traffic.  No additional root protection needed with non-invasive plant species.
Thermoset Membranes EPDM, Single-ply, Sheet-applied, Seamed	10~15 Years	Good	Fair	Poor	Poor	Lightweight and flexible, good for roofs that will not see any foot traffic.
SPF Membranes Sprayed Polyurethane Foam, Liquid-applied, Seamless	10~13 Years	Fair	Good	Poor	Poor	Easy-to-install seamless membrane.  Cannot withstand continuously damp conditions.
FRP Membranes Fibreglass-reinforced plastic, Liquid-applied, Seamless	10~15 Years	Fair	Good	Good	Fair	Quick installation.  Can easily crack if shifted by tremors, earthquakes or settling.

 

 

 

After the membrane is installed you will, of course, have to select the plant species to grow over it.  The variety of plants is too numerous to consider here, but some general guidelines are to choose plants that do not have tap roots, as they require too deep of a substrate, also choose plants which are not generally invasive.

 

Plants should be suited to the local climate, and consideration should be given to the amount of litter created, which might fall on neighboring roofs or walks.

 

Ideally a variety of growth should be planted, species which flower in the winter, along with summer species, some which have insecticidal properties as well as those resistant to rot and fungus.  Having natural pesticides and herbicides will minimize the chances of having an infestation requiring a major remodeling of the roof, and is much like organic gardening, with the added complexity of preserving the underlying,  relatively weak, supporting structure and substrate.

 

It should be considered a lifetime investment, not in cost-savings or the environment, but in challenging hobby work, with lots of planning, diagnosis, logistics and maintenance.

 

 

 

 

Summary

 

Wood is the only roofing material that is sustainable and renewable, of the wood species Western Red Cedar is the most durable.

Compared with other materials like slate, steel, ceramic and asphalt, Western Red Cedar is one of the more durable products available when applied correctly and

maintained, with life spans comparable to the more expensive grades of the more long lived, yet with the ease of installation and low cost of the cheaper and less resilient types.

 

And once again, wood is the only one that is a renewable resource.  It literally grows on trees, and after harvesting the wood, new trees

grow to replace it, using 100% renewable and clean solar energy, plus removing Carbon Dioxide greenhouse gases.

 

Cedar shakes and shingles are usually harvested only from dead trees, killed by fire, wind or other natural processes, or as

a byproduct of logging, recycling waste from logging.  The removal of the dead trees opens new ground for new growth.

These green areas stabilize soil and slopes with their root systems and wind breaks, and the canopy regulates water flows to prevent both drought and flooding.

 

Ceramic, slate, steel and asphalt all require stripping the land of green areas and exposing the underlying structures.

The earth is ground up and hauled away, either to be processed in huge coal and oil burning smoke machines,

or as waste to be piled in huge mounds of dead ground, with no green growth on it to stabilize water flows or slope,

dead ground which has no benefit to the environment, actually decreasing the amount of area available for life.

 

Asphalt requires hot mopping molten tar with a propane burner directed onto your roof, not exactly safe, or clean.

Ceramic and slate require drilling and cutting hard and brittle materials, which often crack or break, but

anyone can swing a hammer, even if you don’t have a hammer a nice round rock would suffice to drive nails through a shingle,

a sharp rock could even split them to size to fit in the contours of the roof.  So easy a cave man could do it.

 

Sustainably harvested wood products are clearly the best solution for those concerned with protecting the environment, and it is also best

suited for those wishing to have an affordable, long-lasting roof.

 

 

 Conclusions

 

For longevity the slate roof is the clear winner, if heavy tiles are selected and good corrosion resistant fasteners are used.  It is, however,

by far the most expensive, so much so that it excludes the majority of the market, both in material cost and specialized installation.  It is the heaviest

roofing material, highest material costs and most difficult to install.

 

The most affordable is the asphalt shingle or roll.  Heavier products are more expensive, but due to the longer life they actually

decrease the cost per year.  The downsides are the aesthetics, poor insulation for both sound and heat, and similar to steel and slate,

the environmental impact and unsustainable extraction of minerals, ores and petroleum is an ever-present concern.  With the more durable thick shingles weight

also becomes a factor.

 

Like asphalt the steel roof can be either a really light weight, cheap, quick roof, which doesn't last long, or an expensive but semi-durable heavy roof.  It shares, too, the down sides of asphalt, it also has poor insulation properties and has a high environmental impact.  More durable types are very expensive, difficult to install and heavy.

 

Clay and cement are both very versatile, available in numerous 3D forms, with various textures and specialized caps and ridges, it can be the best performer aesthetically for the more expensive styles, but also has some major drawbacks; the brittle shingles are easily broken by falling branches, baseballs, etc., but where the low end flat tiles are relatively inexpensive, the more attractive styles which make it so aesthetically pleasing are quite expensive, plus for all types there is expensive specialized installation and high weight loads, requiring robust sub-structures to support the weight of the roof.

 

All of these products have many styles, weights and extra features to accommodate a variety of demands, but no amount of dressing up can overcome the

core problems, the poor insulation characteristics of the materials, and the environmental impact of their manufacture.

 

Considering all of these factors, it is my opinion that the wood shingles are the best all-round product.  It is an excellent performer in all aspects of roofing, it matches or surpasses all other products in all categories considered, plus it is the only one which is harvested in a sustainable and renewable method.  It quite literally grows on trees.

It is the best all-round roofing product. 

 

Wood roofs reduce power consumption for heating because of woods great thermal insulation characteristics, it reduces the consumption of building materials,

because it is light weight compared to products with similar longevity and requires less support structure, reduces cooling costs in the summer because of its reflectivity,

reduces moisture and mold or mildew because it is the only breathable roofing product.

 

When I say wood shingles are an ideal roofing product it is, of course, with the qualification that good raw materials and sustainable processing methods are used.

If inferior or sub-grade raw materials are used, such as White Cedar, Pine or Hemlock or any species cut flat grain or cross grain, then the material could perform poorly

in many aspects.

 

Care must be taken to find a manufacturer that conscientiously applies grading rules to the production of wood shingles.  Those that do usually give a 30 year guarantee on their products, and a few even have a 75 year guarantee for wood shingles.

 

 

 

 

Some important considerations when selecting wood shingles, to ensure the roof performs well, are:

species, grade and style of manufacture.