Trusses, Rafters... What the Heck is the Difference?

By
Home Inspector with Diadem Property Inspections - Serving Southeast Michigan
https://activerain.com/droplet/4QTK

Trusses, Rafters... What the Heck is the Difference?

One of the frequent questions I am asked is: what is the difference between trusses and rafters?

 

Rafters

Rafters are sloped framing members running downard from the peak of the roof all the way to the plates of the outside walls. They are the support for the roof load. Ceiling joists tie the outside walls together, support the ceiling materials for the room below, and secure the bottom ends of the rafters.

Carpenters build conventional rafter roof frames on-site. The rafters are installed one piece at a time.

rafter

 

 

Trusses

Roof trusses are engineered and pre-fabricated, triangulated wood structures which are built in a factory. They are designed to carry the load of a home’s roof to the outside walls, shipped to the construction site, and installed using a crane after the home’s walls have been framed.

The triangles formed by the beams, bars and ties allow the truss to distribute the weight it carries over a broader area.

Trusses come in many varieties. Two are shown below.

 

cambered trussscissor truss

 

According to the National Association of Home Builders (NAHB), conventional roof rafters and ceiling joists are less often used in new home construction these days. In fact, in 2008, about 4 out of 5 homes nationwide were being built with pre-manufactured roof trusses instead of traditional rafters.

 

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Jason Channell     Twitter - Home Inspection LinkedIn Twitter - Home Inspection

Diadem Property Inspections
(888) 699-8710

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Michigan Builder's License 2101198700
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International Indoor Air Quality Commission CC1983 --  Indoor Environmental Certified Consultant

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  1. Not a real person 04/17/2011 04:33 PM
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Rainmaker
1,402,493
Vickie Nagy
Coldwell Banker Residential Real Estate - Palm Springs, CA
Vickie Jean the Palm Springs Condo Queen

This is a really great post. I'll have to follow to see the series I believe might be developing here.

Feb 13, 2011 12:59 PM #1
Rainer
171,130
Robert Butler
Aspect Inspection - Montreal West Island, QC
Montreal Home Inspector | Aspect Inspection

Hi Jason. Being a master carpenter it did't occur to me that there are people out there that don't already know it. I'm an InterNACHI member myself. Their graphics library is great.

Feb 14, 2011 03:24 AM #2
Rainer
130,991
Jason Channell
Diadem Property Inspections - Serving Southeast Michigan - Troy, MI
The House Sleuth

Thanks, Vickie!

Robert, I agree. They have a great graphics library, and a great use policy. I love them.

Feb 14, 2011 04:56 AM #3
Rainer
478,183
Not a real person
San Diego, CA

I bet eventually someone is going to be able to fabricate trusses for these high-end, customized homes. Maybe modular will eventually get to the high-end homes, too.

Mar 07, 2011 02:05 PM #4
Rainer
171,130
Robert Butler
Aspect Inspection - Montreal West Island, QC
Montreal Home Inspector | Aspect Inspection

Russel, they do already. Contractors here just give then the plans and get back a quote for for an all custom set of trusses for the roof framing, engineering all done and a delivery schedule. Usually less than 21 days, some times less than 14, delivered to your site, anywhere (Quebec, Ontario, New York, Vermont, etc.)

Mar 07, 2011 03:39 PM #5
Anonymous
Max
Correction: Both trusses and rafters can be built on-site by framers. Building a truss is only a little more work than a rafter. People order trusses pre-fabricated for the speed. You can build your own trusses for much cheaper though and that comes in really handy with big buildings which they usually can't deliver trusses for anyway due to the height and widths involved with trying to get them on the truck.
Dec 16, 2013 03:42 PM #6
Anonymous
Jackson Willis

It's nice to see the difference between the two laid out. I am about to start building a new house, and I have been trying to make all of these less noticeable decisions lately. I think it will help me to have this information when I talk to the contractor about what i want to do.
http://www.campbelltruss.com

Jan 14, 2015 12:06 PM #7
Anonymous
Danil

thanx, but very little about truss installation, check here http://myrooff.com/how-to-install-roof-trusses/

Sep 30, 2015 05:14 AM #8
Anonymous
Buzz ricketts

Wha kind of roof structure do you think sponge bobs house has?

Feb 11, 2016 06:10 AM #9
Anonymous
dessa frey

Useful ideas ! Speaking of which , people are searching for a MPW Incident Report , my colleague used a template document here https://goo.gl/aieEcN.

Oct 07, 2016 03:29 PM #10
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