HELP! Build Rafters for a Loft in my Cabin

[bkchristopher]

Ok guys, Im new to the building era for the most part.  I'm building a 16x24 cabin at our hunting property and really want a loft area to use for a small bedroom.  I was thinking a 12/12 pitch on the roof.  Should I use regular 8' walls or should I go with 10' walls?   Also, how high up is my ridge board suppose to be with each wall height?  All and any help/info will help.  I plan on building this baby very soon.  Actually the dozer is coming this next Tuesday....


Thanks guys!!!

[Redoverfarm]

You might consider "attic engineered trusses"  if you can't get the details worked out to stick build.  A little more money but IMO well worth it.

[bkchristopher]

Where do i order them from?

[Redoverfarm]

Most lumber yards deal with truss manufacturers.  Give them the style truss (attic) ,demensions of your build , specify the span (16-24"OC) and the amount of overhang you want.  I might recommend that you set on 16"OC to make it a more rigid floor.  You will not get the size room normally the same as your cabin demensions but reduced somewhat in a attic truss.  Example on mine I had a 26' wide structure and was given the option of either a 12' or 15' wide room.  The additional room on either side was used for storage.

[rick91351]

Where do i order them from?

Yellow pages / phone book / local internet link.  They engineer them, stamp the engineering sheet as part of the deal or at least around home they do.

As Redoverfarm says

You might consider "attic engineered trusses"  if you can't get the details worked out to stick build.  A little more money but IMO well worth it.

I might add they are a lot quicker to set as well.  However you might most likely will need something to swing them up with if you can't get a large crew together.  But you might not have to have a crane.  We use a guy with a logging truck where I am from.  His truck has a self loader.  If he is not real busy he will run over if close, and do it on the real cheap.  Especially compared to renting a crane and operator.  Or large farm tractors and loaders work as well.     

[bkchristopher]

I'd really like to make them myself to eliminate the bottom joist of trusses.  I can cut the birdmouths I'm sure.  I just need to know how to figure the height of my ridge board and rafter lengths. 

[rick91351]

I'd really like to make them myself to eliminate the bottom joist of trusses.  I can cut the birdmouths I'm sure.  I just need to know how to figure the height of my ridge board and rafter lengths.

  As far as trusses here is a type I thought you might be interested in.

http://www.truswood.com/attictruss%20pic.htm

Here is a handy download that goes way past 12 12 pitch.  Gives you your rise and runs and all the good stuff.     

http://www.empirelevel.com/images/products/squares/17453.pdf

Here is a link explaining rafter ties and collar ties.  Another reason I like trusses.   

http://www.nachi.org/collar-rafter-ties.htm

Mountain Don and Don_P are the pros here.   

[MountainDon]

In the OP a question was asked about the wall height; 8 feet or 10 feet. If the idea of the 10 foot height is an attempt to increase the headroom in the loft area, there are potential problem issues associated with that. The problems stem from the "stubs" of the studs that stick up above the loft floor joists which are usually inserted at around the 8 foot height*. If you search the forum for "kneewall" you should find some past discussions.

*  Briefly, when walls are built like that the vertical little stubs have outward forces from the rafters applied to them. All rafters do this. However, in a normal wall and rafter design there are ceiling joists or rafter ties spanning from one wall top across to the other. These rafter ties are nailed to the rafters and the rafters connected to the wall tops. A triangle is formed which is very rigid, very strong. Dropping the ties down the wall studs breaks that triangle. That one issue. The other is that loads on the roof will be trying to spread the stud tops outwards. The notches usually cut into the studs for the ledger board that helps support the loft floor joists weaken the studs. All that results in a structure that is weaker than one built in the manner prescribed by building codes. Ohio uses the IRC. on a statewide basis.


If there was a building inspection involved, and if the inspector knows and goes by the code book, that sort of thing will not pass.

[Redoverfarm]

Here are the attic trusses that I have over my garage that I am currently working on.



A view of the inside



Other photographs of them are located @  http://countryplans.com/smf/index.php?topic=12788.0

[MountainDon]

There are some other methods for obtaining better loft headroom. They involve raising the rafter ties rather than lowering them. There are limits to how high a rafter tie can be raised tho' If you to explore that, we can have a look at it later.

[mnboatman]

Ok guys, Im new to the building era for the most part.  I'm building a 16x24 cabin at our hunting property and really want a loft area to use for a small bedroom.  I was thinking a 12/12 pitch on the roof.  Should I use regular 8' walls or should I go with 10' walls?   Also, how high up is my ridge board suppose to be with each wall height?  All and any help/info will help.  I plan on building this baby very soon.  Actually the dozer is coming this next Tuesday....


Thanks guys!!!

On my 16x20' shed I set the bottom of my ridge 66" above my 10 foot walls. That puts  it 90" above the loft floor.



I was going to go a little steeper, but would have lost too much on the eve overhang with my 12' rafters.
To determine my exact height, I laid out a pair of rafters on a flat deck and tried a few different heights until I got the balance of overhang and pitch that I wanted. To go steeper, my rafter blanks would have been 16' with a lot of wasted wood.

Here is a website that can be used to calculate rafters:
http://www.blocklayer.com/Roof/GableEng.aspx

Here is the loft: