Whatever the wall type, trussed rafters are a good choice for the roof framing.
Trusses provide a clear span that makes interior design much more variable, and makes future renovation easier. Trusses can be used in floors as well to provide for a clear span in spaces below. Ease of construction tends to make truss use nearly as inexpensive as other methods. Trusses can be engineered in a great many configurations, and for many roof styles.
A common gable roof truss
They can provide for vaulted ceilings using scissor trusses, studio trusses, or trusses with center bays. and can be built with “heels” to allow room for more insulation in the attic space It is quite rare to see a house built without trusses, in this part of the country.
Attic trusses can be built to allow for extra rooms under the roof in a story and a half configuration.
Spans can exceed eighty feet with timber roof trusses, although, I can’t imagine many houses requiring that wide a clear span.
You can build your own roof trusses (or as an alternative you can visit www.lamcal.com.au), but they are usually made in a factory setting where they are joined together using steel gang nail gusset plates that are pressed into place. They may include steel structural members. Trusses require careful planning and should be engineer designed or approved. Extra care must be taken here, as this is, perhaps, the most important structural element of your house. You have no doubt all heard of roof collapses, or for that matter bridge collapses. These are often the result of compromised, or under designed trusses. Because the cost is not usually great, I prefer to have trusses designed for higher loads than would normally be required. One way is to have your trusses designed for 2 ft centers, but place them on a narrower spacing.
Your truss supplier will need to know the spacing, span, load, eave width, slope, whether you require a heel, and roof type. If your roof is complicated in any way, they will need a set of blueprints. Load is defined as live load and dead load, where dead load is the weight of the roof itself, including any permanently installed or likely to be installed equipment. Live load is temporary loads likely to be encountered, such as workers and construction equipment, or snow accumulations. Slope is usually expressed as inches per foot such as 4.5/12 or 6/12. A heel raises the rafter portion of the truss, and allows for more insulation at the outside perimeter of the attic.
Some basic roof types are the gable, hip, gambrel, mansard, pyramid, saltbox, shed and flat. They may be called different names, and come in many combinations, materials and slopes. They are limited only by the architects imagination, structural integrity and the ability to keep out the weather. Needless to say, the simplest will cost the least. In my opinion, a simpler design can be more easily blended to it’s environment. A complex roof will add interest, and can make a house stand out, if that is your goal.
Some roof types are better suited for different conditions.
A steeply sloping roof with steel cladding is a good choice in high snowfall areas. Low slope or flat roofs will interfere less with sight lines, and will keep the height of a building down. consider carefully before using a bonnet type roof in cold climates. they have a tendency towards ice damming,
A roof may be clad in many materials but the most common in North America are organic asphalt, asphalt/fiberglass shingles, wood shingles, sheet steel or tile. Tile is mostly restricted to the southern and drier areas of the continent. Wood shingles are usually of cedar and have become expensive enough that they are most often used only where appearance makes them desirable.
A flat roof consists of built up layers of tar and sheet material topped with a protective coating of aggregate, or alternately layers of bitumen or fiberglass waterproof sheet, Not common in housing , it is often used on large commercial buildings. More flat roof info is available at this link.
Roll roofing of organic asphalt is available which is inexpensive and quick to apply, and can be used if economy is the major factor.
A shingle roof, today, is placed on a base of 7/16” plywood, or OSB, with a layer of roofing felt. (I prefer a thicker sheathing.) In cold climates, a layer of self adhesive rubberized material is placed at the eaves to prevent leaks caused by ice damming. Valleys may be further reinforced with rubberized material and aluminum or steel sheet.
Modern asphalt/fiberglass shingles can give pleasing contoured visual effects, and can have lifespans of fifty years or more.This is nearly comparable to wood or steel. Wind resistance is quite good. The economical three tab shingles have a lifespan of twenty five years or more. Some shingles will have additives to reduce moss growth. An asphalt roof must be well vented to prevent excess heat build up. Important on other types, as well, for interior comfort. Proper applicaton is critical. Do your research if you plan to do your own.
a roof can be dangerous
Steel and tile roofing usually rests on a framework of furring strips. Both may have a better resistance to UV light and heat than asphalt shingles. It may be more difficult to seal any perforations through the roof. Steel has the added advantages of shedding snow easily and of making a lighter roof. Expansion and contraction at differing temperatures is a factor with steel that can loosen fasteners. Steel is very slippery, and venturing onto a steel roof to remove excess snow can be very dangerous. Tiles tend to be fragile, and although walking on a tile roof is possible, it should be avoided altogether if you can.
There are quite a few color choices with asphalt or steel with the most vibrant tones being available with steel. Tile colors are more limited. Dark colors will absorb more heat, and lighter colors will reflect it. There is a considerable difference, and it should be considered when choosing colors. Extra heat can affect the lifespan of some roofing.
Bolder contours can be achieved with tile or steel, but there is considerable variety in asphalt/fiberglass shingles.
Organic asphalt shingles are made with asphalt impregnated paper and a ceramic aggregate. Asphalt/fiberglass shingles are asphalt and aggregate coating on a fiberglass base. They may be laminated (layered) for architectural appeal, added strength ,and and wind resistance. Both have an adhesive strip to bond them together after they are applied.
Roof tiles may be made of differing materials but traditionally are of ceramic or concrete.
From an environmental point of view, there may not be a lot of difference between the choices, when everything is considered. I believe the best thing to do may be to choose a product with a longer life span, particularly where the cost differential is not great. I would like to see someone do a detailed analysis in this regard.
This is a large subject for one blog post. If you would like more information, please use the links I have provided.
For an interesting look at how things are done down under, check out this link
Bill said he couldn’t make any money building a roof——-Too much overhead.
It is snowing heavily outside my window right now, and I am pretty happy to have a roof over my head.