truss spacing

RebelPride · Aug 31, 2004

I am planning on building a 24 x 24 pole barn, using a metal roof installed on top of 2 x 4 purlins. I am not sure how far apart the trusses should be placed. Some of the posts that I have read show trusses being placed anywhere from 16 inches to 4 feet. What is the correct way to determine their placement?

_RaT_ · Aug 31, 2004

If these are manufactured trusses, it will be engineered and the spacing will be given to you based on that engineering. It will take into account loads from snow if any, roofing material and of course span(s). Sometimes trusses are spaced at 24", sometimes more. It depends on many factors including the size and type of wood used.

RebelPride · Aug 31, 2004

They will be enginered trusses, so what you are saying is, they will make them to your specifications, or that they are already built to there specs, and are spaced according to the load?

Glenn9643 · Aug 31, 2004

Rick,
What works for me might not for you, but my two shops and houseboat have trusses on 4' centers. Built my own trusses using SYP 2x4. I've also used treated 1x4 for purlin instead of 2x4 and it works well as the metal roof is relatively lightweight and we don't have a snow load problem in the south.

Gatorboy · Aug 31, 2004

What is the correct way to determine their placement? 

It is based on several factors, for example, snow load, roof material, slope, type of wood, what size wood for chords and webs, etc.

I bought this publication called Designs for Glued Trusses. It was $7 and is full of truss designs to aid you in determining the answers you seek.

Egon · Aug 31, 2004

Go check with the fellow selling you the trusses. You will get all the information you need.

A 24 foot span with a rise of one foot for every four feet of run should be a very common span if that is what you intend on using.

Egon

Nasty135 · Aug 31, 2004

Rebelpride, I live in md. and we have had snowfalls up to 16"-18" at times and my barn roof is metal on rough cut 1"x6" purlins with trusses on 4' centers and I have had no problems. /forums/images/graemlins/smile.gif See pic I would think you should be fine.But I'm not an engineer! /forums/images/graemlins/ooo.gif

chucko · Aug 31, 2004

( They will be enginered trusses, so what you are saying is, they will make them to your specifications, or that they are already built to there specs, and are spaced according to the load? )

Trusses, something I know
You tell them what you want and they will see if it works by eng-ing them on the computer. If they do not work like you wanted they will let you know what works. It is all part of the quote process. Most places do not stock trusses because everyone wants something a little longer shorts steeper...

boustany · Sep 1, 2004

As said, the truss manufacturer tells you what the spacing is. Based on your description, I'd guess 24". If you went with a heavy roof (say tile) they'd probably be 16". Usually wider truss spacings are used when you timber frame the roof.

By the way - ask about attic trusses. They usually do the same span, cost only a bit more, and leave you with loads of useable storage space in the attic. My barn attic has a 12' x 7' x 40 storage space because I went with attic trusses. All I had to do was add a floor, but that can be done later, if you want.

fishman · Sep 1, 2004

Boustany,

The attic truss really intrigues me, as I am in the process of planning a 30x40 shop, and I NEED open attic space. Do you know where to get the plans for a truss like that? How about a picture? I'm familiar with the Fink-style trusses and they look easy to build, don't know about these attic-style trusses.