AndyGump

HI Neal, you are polite, on this topic I guess we will just have to agree to disagree I guess.

It sounds like you are describing a purlin rather than a collar tie but of course those run perpendicular to the rafters.


Andy.

nealtw

Purlins are supported with bairing points to the ground. Low pitch roofs have nee walls down to bairing walls.
I found this for you.
http://www.managemylife.com/mmh/questions/112690-collar-ties

AndyGump

I have to say, who ever the self-described "Expert" is in the link you provided has a lot of things really mixed up.

A collar tie runs from a rafter on one side of the ridge board to the opposing rafter on the other side. Are usually connected with 16d nails, are required to be minimum 2x4 lumber now but for a long time 1 x material was O.K. to use. They are usually about 1/3 the way down from the ridge board too.
Now rafter ties are used to keep the walls from spreading and ties the bottoms of the rafters, normally your ceiling joists perform this function in most homes but some homes have ceiling joists that are perpendicular to the roof rafters, hence the use of rafter ties in these situations.

Purlins run perpendicular to the rafters, usually at about the mid point of the rafters, are a minimum of the depth of the rafters and are supported by 2x4 or greater bracing on 48" centers to a bearing wall that will carry the load of part of the roof to the foundation.

Andy.

nealtw

A collar tie runs from a rafter on one side of the ridge board to the opposing rafter on the other side. Are usually connected with 16d nails, are required to be minimum 2x4 lumber now but for a long time 1 x material was O.K. to use. They are usually about 1/3 the way down from the ridge board too.
Your first post indicated this can be removed. If you are suggesting to build a knee wall to barring, an angle wall to barring or a purlin supported to barring wall yes, but just remove it, not a chance. Not without checking loads live and dead and the span of the rafter.
BTW For walls that do not have rafters landing on them. A 1x4 or 2x4 nailed across the ceiling joists from wall to wall hold the wall straight. Commonly called cat walk placed no more than 10 ft apart are found in rafter houses and houses with trusses and homeowners should be aware of their importance when applying a deck to the ceiling joists.

BridgeMan

If a collar tie is to perform as a structural member, it must be rigidly attached to rafters at each end with through-bolts to be most effective. A flimsy 1x of any depth will not do well, as it is prone to bowing and buckling when acting in compression to resist vertical rafter forces.

nealtw

If the only concern is lift do to wind the tie will only prevent tension and a 1/4 is acceptable, nailed. More than 1/3 from the top.
If the rafter is overspanned, a 2x4 or 2x6 will be called for somewhere between 1/3 and 1/2 from the top to serve as tension and compression, bolts are seldom called for.

The plans for new construction usually read something like trusses supplied by others or (built on site) The city will ask for an engineered design on the roof, nothing more to think about.
The bottom line is if it looks like structure, it likely is and don't remove it until you know what the h!!! you are doing.