Wood Shake Roof

In North America shakes are typically made from Western Red Cedar (Thuja plicata), while in Scandinavia and Central Europe they are more commonly made from pine (Pinus sylvestris). There are various types of shakes, the main differentiating feature between shakes and other types of shingles is that shakes are split while most shingles are sawn on all sides. The sizes also vary from country to country; in North America shakes are usually made in 24-inch lengths – the most common, 18-inch barn shake, or even 48-inch shakes, which are typically used for siding. In Scandinavia shakes, traditionally used only for roofing, are generally smaller than in North America, measuring 13-16 inches long, 4-6 inches wide and 1/8 thick.[1] Likewise wooden shingles are manufactured in differing lengths, in North America, 15-inch, 18-inch and 24 inches.

Both shakes and wooden shingles are typically cut from salvage logs, dead trees which were left from previous logging operations, or selective logging of dead trees; this depends on area licensing.

Asphalt Roof

Two types of asphalt shingles are used: organic and fiberglass or glass fiber. Organic shingles are generally paper (waste paper) saturated with asphalt to make it waterproof, then a top coating of adhesive asphalt is applied and ceramic granules are then embedded. In the case of algae-resistant shingles, a portion of the granules contain leachable copper ceramically coated, designed to protect against discoloration from algae on the roof. This does not protect from moss growth but does slow the growth. Moss likes to feed on algae and any other debris on the roof. Most manufactures offer a 5- to 10-year warranty against algae growth; 3M (scotchgard TM) offers a 20-year warranty.

Shingles are judged by warranty and ASTM test standards. Organic shingles contain around 40% more asphalt per square (100 sq ft.) than fiberglass shingles. But this extra needed asphalt makes them less environmentally friendly (despite its “organic” nickname). The paper-based nature of “organic” shingles leaves them more prone to fire damage, and their highest FM rating for fire is class “B”. Shingle durability is ranked by warranted life, ranging from 20 years to 50 years; in some cases lifetime warranties are available.

Fiberglass shingles have a base layer of glass fiber reinforcing mat. The mat is made from wet, random-laid fiberglass bonded with urea-formaldehyde resin. The mat is then coated with asphalt which contains mineral fillers and makes the fiberglass shingle waterproof. Fiberglass shingles typically obtain a class “A” fire rating as the fiberglass mat resists fire better than organic/paper mats. Fiberglass reinforcement was devised as the replacement for asbestos paper reinforcement of roofing shingles and typically ranges from 1.8 to 2.3 pounds/square foot.

The older organic (wood and paper pulp product) versions were very durable and hard to tear, an important property when considering wind uplift of shingles in heavy storms. Fiberglass is slowly replacing felt reinforcement in Canada and has replaced mostly all in the United States. Widespread hurricane damage in Florida during the 1990s prompted the industry to adhere to a 1700-gram tear value on finished asphalt shingles.

A newer design of fiberglass asphalt shingle, called laminated or architectural, uses two distinct layers which are bonded together with asphalt sealant. Laminate shingles are heavier, more expensive, and arguably more durable than traditional 3-tab shingle designs. Laminated shingles also give a more varied, contoured visual effect to a roof surface.

Per 2003 International Building Code Sections 1507.2.1 and 1507.2.2, asphalt shingles shall only be used on roof slopes of two units vertical in 12 units horizontal (17% slope) or greater. Asphalt shingles shall be fastened to solidly sheathed decks.

Tile Roof

Roof tiles are designed mainly to keep out rain, and are traditionally made from locally available materials such as clay or slate. Modern materials such as concrete and plastic are also used and some clay tiles have a waterproof glaze. A large number of shapes (or “profiles”) of roof tiles have evolved. These include:

  • Flat tiles – the simplest type, which are laid in regular overlapping rows. An example of this is the clay-made “beaver-tail” tile (German Biberschwanz), common in Southern Germany. The profile of flat tiles is suitable for stone and wooden tiles, and most recently, solar cells.
  • Imbrex and tegula, an ancient Roman pattern of curved and flat tiles that make rain channels on a roof.
  • Roman tiles – flat in the middle, with a concave curve at one end at a convex curve at the other, to allow interlocking.
  • Pantiles – with an S-shaped profile, allowing adjacent tiles to interlock. These result in a ridged pattern resembling a ploughed field. An example of this is the “double Roman” tile, dating from the late 19th century in England and USA.
  • Mission or barrel tiles are semi-cylindrical tiles made by forming clay around a curved surface, often a log or one’s thigh, and laid in alternating columns of convex and concave tiles.

Roof tiles are ‘hung’ from the framework of a roof by fixing them with nails. The tiles are usually hung in parallel rows, with each row overlapping the row below it to exclude rainwater and to cover the nails that hold the row below.

There are also roof tiles for special positions, particularly where the planes of the several pitches meet. They include ridge, hip and valley tiles.

Metal Roof

Metal roof sheeting in the form of Corrugated galvanized steel was a great aid to opening up America in its early days. This is still happening today in parts of the developing world.

Metal roofing is usually easily applied over an existing roof. Especially in situations where labor cost cutting is essential, the added value of not having to remove the existing roof material can be of a large help.

Many different types of coatings are used to coat metal panels. These coatings are most often polymeric (elastomeric) coatings. Each coating type and brand has its own advantages and disadvantages. Recent advances in coatings have allowed Kynar based coatings to become readily available. Kynar has been by far the longest lasting metal roofing paint available so these new coatings have great promise.

Commercial Flat Roof

A flat roof is a type of covering of a building. In contrast to the sloped form of a roof, a flat roof is horizontal or nearly horizontal. Materials that cover flat roofs should allow the water to run off freely from a very slight inclination.[1]

Traditionally flat roofs would use a tar and gravel based surface which, as long as there was no pooling of water, was sufficient to prevent penetration. However, these surfaces would tend to fail in colder climates, where ice dams and the like could block the flow of water. Similarly, they tend to be sensitive to sagging of the roof reversing the subtle grading of the surface.

Modern flat roofs tend to use a continuous membrane covering which can better resist pools of standing water. These membranes are applied as a continuous sheet where possible, though sealants and adhesives are available to allow for bonding multiple sheets and dealing with structures penetrating the roof surface. Far more expensive flat roof options include sealed metal roofs using copper or tin. These are soldered interlocking systems of metal panels.

Modernist architecture often viewed the flat roof as a living area. Le Corbusier’s theoretical works, particularly Vers une Architecture, and the influential Villa Savoye and Unité d’Habitation prominently feature rooftop terraces. That said, Villa Savoye’s roof commenced leaking almost immediately after the Savoye family moved in. Le Corbusier only narrowly avoided a lawsuit from the family due to the fact they had to flee the country as France succumbed to the German Army in WWII.

Flat roofs tend to be sensitive to human traffic. Anything which produces a crack or puncture in the surface can quite readily lead to leaks. In other words, this sort of roof has a major weakness to failure from subsequent work done on the roof – such as upgrading building HVAC systems and so forth. It is thus not generally advisable to use a flat roof as a living area unless steps are taken to protect the roofing membrane from those using the area, for example, by building a wooden deck over the surface or using paving stones or similar materials to protect the roof membrane. It is not advisable in general to have living areas directly under such a roof either, due to the high likelihood of eventual leakage.

One of the more interesting (re)emerging methods of protecting the roofing membrane is to use a layer of topsoil and grasses. Care should be taken not to plant anything the roots of which will penetrate the membrane surface. The green roof interestingly enough, tends to trap moisture on the roof, but keeps it up in the soil and plants, rather than having it pool down on the membrane surface.