Are ridge ties needed in post & beam garage?

[guy48065]

I've added a 24W x 14L addition on to the rear of my 32 x 24 detached workshop. Constructed with 6x6 posts & double 2x12 beams like the main building. Unlike the main section the addition is unheated storage so no ceiling. The builder installed one ridge tie made from a single spliced 2x4 to span the top of the beams in the center of the 14' span. Do the massive posts & thick beams eliminate almost all the need for ridge ties when there are no ceiling joists present?

I'm probably going to add 2 4' wide storage lofts so this will add 2 more ties but I still want to know what's required to keep the walls straight and the roof from sagging.

 

[premierplayer]

the 6x posts an 12" beams hold it up, they don't keep it from spreading appart, yes, you need collar ties if engineered truss's were not used.

 

[guy48065]

OK but I'm asking about rafter ties.

 

[ddawg16]

OK but I'm asking about rafter ties.

Same difference.

 

[guy48065]

Same difference.

Ummm...no.
http://www.nachi.org/collar-rafter-ties.htm

 

[kbs2244]

If your double 2x12 beam is the ridge then you have a ridge beam roof vs. a ridge board roof.
This is common in post and beam construction.
IMHO you are very lucky.

Note that in Guy’s link the ridge is noted to be non-structural.
They are just something to line up the top ends of the rafters on.
This is called the ridge board and I have seen a 1x 6 used.
That is the most common roof and you need the joists to keep the walls from spreading under the outward pressure of the rafters.

But if your 2x12 beam is supported at both ends by posts it becomes structural.
When the rafters are installed they are under tension vs. the compressive load of the light weight ridge board style.
So the rafters are what keep the walls from spreading.
Structurally you don’t need either joists of collar ties.
If you have one it was probably put in place to keep things square during construction.

 

[Falcon67]

KBS2244 has it down. Collar ties will not hold a ridge board roof together without joists. Joists are technically rafter ties and as those move up off the plate, the load on the rafters in a ridge board constructed roof goes up. As noted, if the building has a ridge beam and it supported structurally, then you need neither collar ties nor joists.

 

[guy48065]

I have a non-structural ridge board, held up only by the rafters. The beams I refer to are the top plates the rafters rest on. I don't believe presence or position of rafter ties (ceiling joists) or collar ties has any effect on the rafter load. Rafter ties just keep that load which is transferred to the top plate from pushing it out, causing the walls to bow and ridge to sag. All collar ties do is hold the rafters down against lifting in a wind storm. They aren't even required if there are metal storm ties attaching the rafter boards to the ridge board. That is if you trust those scrawny little sheet metal ties

Still would like to know if my builder got it right or skimped by only installing one rafter tie.

 

[ddawg16]

Same difference.

Ummm...no.
http://www.nachi.org/collar-rafter-ties.htm

Brain fart....that is what I get for being tired and answering in a rush...

But....if the collar ties are low enough (like in my roof), they sort of act like rafter ties....

Still a brain fart though