What is the difference between trusses and rafters?

Question

Ive been doing drafting now for a couple years.. I need to learn the basics such as... Roof framing, Foundations and just basic knowledge about construction so I dont sound inexperienced in the presence of a contractor. Thanks... Any good books that would teach me that sort of stuff ? thanks

Answer 1

A rafter is a single board that runs from the outside wall up to the ridge....It may or may not have supports below it.  

A truss is a unit which has single board that runs from the outside wall up to the ridge, then another board returns down to the opposite outside wall....(sounds the same, but)  the truss has a series of engineered triangular shaped supports, below it, and includes the roof joist.   Advantage: requires smaller size lumber.  Stronger, and capable of large spans, without center support.    Google "truss" and you will see the variety of designs available.  Downside, may require a crane to erect.

Answer 2

Trusses are engineered roof systems built by  specs for your house and delivered, rafters are boards running to a ridge board from your wall exterior top plates and fabricated on the job site.

ADD

Trusses are pre-fab and rafters are conventional framed on site.

Answer 3

Ask the question in the engineering section. Those guys are very good.

Answer 4

http://www.ehow.com/guide_12-home-garden...

Answer 5

Doctor feelgood nailed it word for word what I would have said. A couple more tidbits:

I have always preferred rafters because of the enormous ceiling space you can get, I love wide open rooms, that's just me.  With trusses you can't get a full cathedral ceiling. They engineer trusses known as "scissor" trusses where instead of a horizontal board across the top plates they angle the truss supports in a manner where you have a bit of a cathedral ceiling.

Trusses put up by professionals can be run in no time with a crane, rafters are tough because you need to be able to put up the ridge board before setting your rafters and to some it can be tricky (not to mention the massive weight of the rafters themselves haha)

It really comes down to preference, they both have their pros and cons. But like the other poster said, a truss is an engineered unit of many boards designed to be thrown up and anchored down with ease, with a great amount of strength and stability, while rafters are just long boards individualy erected and fixed to a ridgeboard creating the peak of the roof pitch.

Answer 6

Rafters are a single piece of lumber that span from beam to beam or beam to wall or wall to wall.  The may be sloped or flat.  Although flat rafters are usually called joist.  Typically roof rafters are 2x8's or 2x10's depending on the distance and the load applied. When using rafters or joists, this is called conventional framing.  Trusses do the same as rafters but consist of a top chord, bottom chord, and web members.  The top chord and web members are usually constructed out of 2x4's and the bottom chord is constructed out of 2x4 or 2x6.  Because of the shape of trusses, trusses can span much further then rafters and can support much more weight.  Trusses can be used for roofs or floors and can span large distances, some wood roof trusses can span 60 feet.  Trusses are typically built in a factory and shipped out to the job site.  Sounds like you will be visiting a home construction site.  Here is a glossary of construction terms.

http://www.homebuildingmanual.com/Glossa...

The best knowledge though comes from actually going to the site and observing with someone who can point out aspects of construction.