Collar Ties - framing

[OlJarhead]

Hope this isn't too redundant but I have this question:

When framing collar ties I'm assuming the following:

1. 2x10d nails nailed to the rafter
2. 2x4 ties
3. Framed at 7-8 feet in height from the floor of the loft (26" knee wall) -- or roughly half way up the rafter leaving head room.

Is there anything else I should consider?

[MountainDon]

IRC2008

collar ties to rafter, face nail,  3 - 10D (3" x .128") nails


Collar ties are usually higher up and may be replaced with 1 1/4" x 20 gauge ridge straps. In your application I think you are also asking them to restrain the rafters, to keep them from spreading at the upper wall plate connection.  Perhaps John R or Don_P will have something to add to that.  

[OlJarhead]

IRC2008

collar ties to rafter, face nail,  3 - 10D (3" x .128") nails


Collar ties are usually higher up and may be replaced with 1 1/4" x 20 gauge ridge straps. In your application I think you are also asking them to restrain the rafters, to keep them from spreading at the upper wall plate connection.   Perhaps Don_P will have something to add to that. 

3 huh?  OK cool -- I think JR's plans say every 4 feet -- any reason to go every 2 feet?

[John Raabe]

2' o/c will give you more wind bracing, 4' is traditional and a minimum.

[OlJarhead]

2' o/c will give you more wind bracing, 4' is traditional and a minimum.

Thanks -- I may do that.

We got them in at every 4 feet except the end rafters (gabled ends) as the cut outs for the look out 2x4's are right were I was putting my collar ties so I'll have to notch those or cut them differently -- I'll figure something out.

Feels good to have the 5 in that we have now though

[considerations]

Woops - John, do I need collar ties as well?  14 x 24 Olympic peninsula.  10' contiguous stud walls 7'6" to bottom of ceiling joists.

[OlJarhead]

Woops - John, do I need collar ties as well?  14 x 24 Olympic peninsula.  10' contiguous stud walls 7'6" to bottom of ceiling joists.

I think so but John will have to be 'your final answer'.

It's easy peasy to install if you still haven't finished the walls though, and one every four feet should suffice -- looking at the plans that appears to be the recommendation.

One thing I did, which may not be right, is I used 2x4's for collar ties.  I'm curious what John and Don think about that since I'm using 2x6 rafters....

[OlJarhead]

You can see the ties every 4 feet here.

I nailed them onto the rafters using 3 10d nails and an air nailer   Made life easy.

I also set them at 7 feet high becuase I don't expect anyone taller then that in the loft and it was easy to put them there

Basically I just measured up from the floor to 7' made a mark then measured across to the other side where I had a mark also, cut the tie with 45 degree angles and put it in place, checked level, decided it would work, nailed it in place and made the rest the same size.

Of course, this cabin might be a bit rough for some as I'm sure my ties aren't perfect across the roof.  There are always little variations in things and so cutting them out at once, leveling and nailing while faster, might leave 1/4" high or low every 4 feet.  But I'm ok with that

Cheers
Erik

[John Raabe]

If you have ceiling joists tying the rafters together you do not need collar ties as well.

[OlJarhead]

If you have ceiling joists tying the rafters together you do not need collar ties as well.

In my case with the loft at 7'6" and the top of the wall at 10' 4 1/2" there are no ceiling joists nailed to rafters.  So I think I have to have collar ties....

[Don_P]

Where ceiling joists are not provided as ties at the top plate they may be raised as much as 1/3 of the roof height to prevent spreading thrust.

Collar ties are required every 4' in the upper third of roof height or metal straps over the top to prevent uplift.

If this cannot be done a ridgebeam capable of supporting the roof load is used. Collar ties or straps would still be required.

[OlJarhead]

Where ceiling joists are not provided as ties at the top plate they may be raised as much as 1/3 of the roof height to prevent spreading thrust.

Collar ties are required every 4' in the upper third of roof height or metal straps over the top to prevent uplift.

If this cannot be done a ridgebeam capable of supporting the roof load is used. Collar ties or straps would still be required.

I have a loft with joists a little more then 2' below the top plates -- I beleive that will hold the walls together (right?) and then with the collar ties about 2' below the ridge. 

[John Raabe]

A collar tie that high does help tie and triangulate the rafters but doesn't meet the lower 1/3 rule of thumb. You can help stiffen the rafter connection by using a metal anchor or strap between the rafter seat and the top plates at the wall. I feel this combination is fine for most loads but it is a complex relationship and I have not done engineering on it.

It is what I did in my own house and the inspector passed it without engineering.

You could also take the problem to the local truss company and they can provide trusses that will meet your local loads without you having to kick this messy issue down the road again. They have their own engineering program and will provide printouts for the inspector.

PS - looking at your photo it will help to put a tie on each rafter pair.

[OlJarhead]

A collar tie that high does help tie and triangulate the rafters but doesn't meet the lower 1/3 rule of thumb. You can help stiffen the rafter connection by using a metal anchor or strap between the rafter seat and the top plates at the wall. I feel this combination is fine for most loads but it is a complex relationship and I have not done engineering on it.

It is what I did in my own house and the inspector passed it without engineering.

You could also take the problem to the local truss company and they can provide trusses that will meet your local loads without you having to kick this messy issue down the road again. They have their own engineering program and will provide printouts for the inspector.

PS - looking at your photo it will help to put a tie on each rafter pair.

OK now I'm confused.

I've seen lots of cabins based on the 14x24 builders plan that have collar ties up this high and then loft joists 2 feet below the top of the wall in the gallery (nash comes to mind but there are others I'm sure)....so what did they do?

Putting a collar tie in the bottom 3rd means you won't have any loft space to use.  1/3 up the rafter would be at the 7 foot mark (down the rafter) or just a few feet off the floor.  Makes the loft useless.

So we need a drawing or something -- but looking at the plans I don't see this at all. 

[RainDog]

You're not alone, OlJarhead. It's throwin' me too.

[John Raabe]

In the Little House plans the loft joists (when there is a loft) or the exposed rafter tie (when there is a cathedral ceiling) are attached to the rafters and sit on top of the wall plates. This perfectly ties the rafters into a triangle.

When you balloon frame the higher walls and support the loft joists on a ledger you reduce the function of the rafter tie that the loft joists provide when they are nailed directly into the rafters. This is the case with the 1-1/2 story house and the 16' wide studio house in the Victoria Cottage plans. The taller the sidewall studs and the higher the pony wall in the loft, the more outward pressure on that wall by a standard untied rafter. That is why both of those house plans have site built trusses (or commercial trusses) called out.

I do have a detail on page 11 of the 1-1/2 story plans booklet that uses a higher collar tie on each rafter. It has a short pony wall.

When inventing you own framing layout you want to triangulate the rafter with the collar tie and attach these with metal hardware such as A35 anchors to the wall plates. You can also build a rafter - collar tie frame tied into a truss with plywood gussets such as I use in the 1-1/2 story plan or the Victoria Studio House.

You are safest building a plan as drawn because when you combine things from different plans such as doing a tall balloon framed wall on a Little House project you are changing the dynamics of the house. While the loads are small I am not worried. But, in more heavily loaded situations (hurricane alley or 6' of snow) you should get local advice and engineering help.

Hope that helps

[OlJarhead]

OK I think I get it now -- so using hurricane ties is probably a good idea in this case as it ads to the strength of the rafter to wall connection?

I could lower the collar ties and make the ceiling hieght 6.5' instead of 7 feet but that won't get the collar ties into the bottom 3rd of the rafter either.

So I'm thinking collar ties on all rafters (instead of every 4 feet), hurricane ties and then not worrying about it

At least I can be certain the walls will stay together becuase of the loft joists right?

[John Raabe]

Yes, that's what I would do. Don't lower the ceiling any more.

Sorry for any confusion I caused.