Ridge Beams

[BG999]

I am renovating an old milk house from the 1920s, turning it into an insulated shed/office. It is 14' x 14'. I recently re-roofed it, and in the process added a new layer of OSB under the shingles. I just realized, though, that the rafters simply butt up against one another at the peak -- there is no ridge board nor ridge beam. The structure has rafter ties and no collar ties. Since the building has survived nearly a century of winters, it is apparently stable. But now that I'm renovating, should I use the opportunity to upgrade the design? Should I, for example, try to add a ridge beam under the join between the pairs of rafters?  Or do I leave well enough alone?

[Jim_Rogers]

You're going to have to explain to me what the difference is between a collar tie and a rafter tie.

I would imagine it is the elevation of the timber but you should explain that to me.
And please be specific.

Jim Rogers

[starmac]

Well if it ain't broke???

[ChugiakTinkerer]

Welcome to the forum!

A picture or sketch would do wonders for helping us understand better.  Also what is the condition of the side walls?  Any evidence of bowing, or sagging along the roof line?

[timberwrestler]

In short, you're fine.  It's only 14' wide.  It's fine for the rafters to butt against each other.  A rafter board just makes it easier to nail.  A traditional timber frame might have a five sided ridge (or something similar), and unless it's posted down, it's just a fancy version of the board.  A structural ridge is an entirely different thing, and overkill for this building.

I would call a rafter tie a member in the bottom third of the roof, that ties the walls together.  A collar tie is higher, and doesn't tie the walls together, but is in compression, and helps the rafters with bending. 

[flyingparks]

Let's see a photo! ???

[rasman57]

You're going to have to explain to me what the difference is between a collar tie and a rafter tie.

I would imagine it is the elevation of the timber but you should explain that to me.
And please be specific.

Jim Rogers

Not the original poster, but Jim this is what I was taught.. FWIW    Not sure how this affects BG999's project.
Collar ties and rafter ties are both horizontal roof-framing members, each with different purposes and requirements.



Collar Ties.... ties are designed to tie together the tops of opposing rafters. This helps brace the roof framing against uplift caused by wind. Collar ties must be placed in the upper third of the roof.

Other facts about collar ties:

They may or may not be required, depending on jurisdiction. Inspectors should not call out lack of collar ties as a defect unless they know that collar ties were required in the jurisdiction in which the home is located at the time the home was built.

Collar ties are probably not needed if metal connectors were used to fasten the rafters to the ridge.
Where they are required, they should be installed on every other rafter where rafters are on 24-inch centers. 

The 2006 International Residential Code (IRC) requires they have a minimum nominal dimension of 1-inch x 4-inch.

Collar ties, contrary to popular belief, do not prevent walls from spreading.

Rafter Ties are designed to tie together the bottoms of opposing rafters. This helps keep walls from spreading due to the weight of the roof. When the walls spread, the ridge will sag. A sagging ridge is one clue that the home may lack adequate rafter ties. Rafter ties form the bottom chord of a simple triangular roof truss. They should be placed as low as possible in the roof framing.

Other facts about rafter ties:

Rafter ties are always required unless the roof has a structural (self-supporting) ridge, or is built using engineered trusses. A lack of rafter ties is a serious structural issue in a conventionally framed roof.
In most homes, the ceiling joists also serve as the rafter ties.

Where rafters are oriented perpendicular to the ceiling joists, rafter ties should be installed just above the ceiling joists. The ties usually rest on the joists.

When rafters are installed on 24-inch centers, rafter ties are typically installed every other rafter.

It's not unusual to see rafter ties of either 2-inch by 4-inch or 2-inch by 6-inch. The 2006 IRC requires them to be at least 2-inch by 4-inch.

In summary, collar ties and rafter ties perform different functions but are both essential roof-framing members.

[Stone]

Yeah a picture would go a long way. It sounds like what you have is just a homemade truss. Adding a ridge board at this point would be a PIA and not needed. Are the collar ties up near the top? If so you should be fine. A 2x6 up on edge from plate to plate/heel to heel screwed into the rafter will help stiffen things up which will double as a ceiling joist to hang whatever you use to finish the ceiling off with, sheetrock, car siding, etc,etc.
Just make sure you nub the top corners of the joists to match the pitch of the roof.