# Attic Cross Member Question



## Rmwoiak (Feb 18, 2013)

Guys,

I am getting ready to put some flooring down in my attic to make more room for storage. I have three cross members (?) in my attic that I was unsure about. I have included a few pictures below. They are located in my town house which was a gable roof. The cross members are about 8in tall but only a 1/2 in thick. They don't seem very sturdy so I cant imagine they are structural. I wanted to see if anyone could identify them and see if I am able to safely remove them. Thanks guys.


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## nealtw (Feb 18, 2013)

They are ties to stop the roof from sagging. They are very much structural and should not be removed.


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## Rmwoiak (Feb 18, 2013)

Thanks, I just wanted to double check before I did anything dumb.


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## Wuzzat? (Feb 18, 2013)

How are they fastened at the ends?  For structural purposes I'd think they'd use through bolts and thicker wood and a lot more of them.  

Since the force spreading the roof is uniform, the horizontal roof line should look wavy when sighted at right angles to these boards if these are resisting a tensile force.  The roof width would then be narrower at the few places where these strips are anchored.


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## JoeD (Feb 18, 2013)

Ignore Wuzzat.
They are called collar ties and they are needed.

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


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## Wuzzat? (Feb 18, 2013)

Ignore JoeD. 

The ones on my porch are 2 bys, three sandwiched with a center one for appearance.  At least 12 nails at each end.


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## poppa (Feb 18, 2013)

I'm an old carpenter and we called those wind braces and put one on every other set of rafters. You really should put more in you don't have enough.


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## CallMeVilla (Feb 23, 2013)

When I built a large shed last year, I used 2x4 lumber for the ties to the rafters.  Solid roof.  Never going to sag and the wind will not lift it.

KEEP those ties in place.

PS If you are putting down plywood for storage, DO NOT lay the wood over any wires which are sitting on top of the ceiling joists.  This could be hazardous!


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## AndyGump (Feb 24, 2013)

If you want to do away with them you would have to get a permit to make a relatively small change like this and install 20 gauge x 1-1/4" straps across the ridge from rafter to rafter.

Andy.


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## nealtw (Feb 25, 2013)

Andy: I would like to be polite but, wrong. Collar ties are placed in steep roofs  at the half way from the birds mouth to the peak to supply support against sag. By adding this support, they make the span of the rafter 1/2 of the full length. Your straps would be added to prevent failure in high winds and is a different problem.


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## AndyGump (Feb 25, 2013)

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.


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## nealtw (Feb 25, 2013)

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


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## AndyGump (Feb 26, 2013)

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.


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## nealtw (Feb 26, 2013)

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.


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## BridgeMan (Mar 4, 2013)

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.


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## nealtw (Mar 4, 2013)

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.


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