In y’alls experience, what are common materials for ridge beams? I am told that dimensional lumber (i.e. a 2 x 10 doug fir) is “standard” and that LVLs are not all that common?
Is someone just yanking my chain here or is there something to that?
Thanks!
Ed
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Replies
We use LVLs for structural ridge beams when framing vaults that will not allow for collar ties. Typically we have an engineer size the beam because we really don't want the roof to saddle-back. When framing a roof over a room that will have ceiling joists, we use dimensional lumber. In this case the ridge board does not need to carry such a load.
Very good explanation. Most people think the terms ridge beam and ridge board are interchangable, which they are not.
They are generally engineered lumber around here.
In my shop I used a 6x18 glulam and some big PSLs for dormer headers. The straightness of that material is nice. In my last house I reframed half the roof using a 4x12-24' with a couple of intermediate posts. The engineered stuff can span farther than sawn lumber of the same size, and it costs more.
2x is standard, engineered for structural ridges when the floor system can't hold the walls from spreading.
>> 2x is standard, engineered for structural ridges when the floor system can't hold the walls from spreading. <<What does the floor system have to do with walls spreading?Joe Carola
Well, many of the houses I design and build have finished space under the rafters. The rafters come down to the same plate as the floor joists or sometimes as a raised heel on top of the floor system. The floor system of the "attic" is also the rafter tie that hold the bottom of the rafters together.
There are plenty of situations where that's not true and a structural ridge is required.
Mike Maines
>> Well, many of the houses I design and build have finished space under the rafters. The rafters come down to the same plate as the floor joists or sometimes as a raised heel on top of the floor system. The floor system of the "attic" is also the rafter tie that hold the bottom of the rafters together. <<Mike,Your just talking normal framing then. Houses like your talking about are Cape Cods where the rafters either sit on the top plate or on top of the joists. Either way the walls can't ever push out because the floor joists are holding them together.If the rafters are sitting on the top plate and nailed into the joists, the wall can't push out.If the rafters sit on top I always use hurricane ties and we nail angle 2x's along side the joists running the same direction and the joists running opposite when nail blocking in and nail the angle 2x's to them. This keeps the rafters from pushing off the plates.Either way you do it you don't need a structural ridge for a Cape unless you throw a dormer on one side and have it full cathedral. If you don't have the dormer full cathedral, you don't need a structural ridge.Joe Carola
We always use what you call hurricane ties, no matter what. Those Simpson H2.5 and similar variations are priceless.
Framer, great post, but a couple of questions.
You say unless you have a cathedral you don't need a ridge beam. Two questions:
1. is this true regardless of how high up the rafter you nail in your rafter/collar (don't recall which term is appropriate in this case)? In some cases your ties have to be pretty close to the ridge in order to get an 8 foot ceiling in the space.
2. Secondly, as a devil's advocate if you tie the rafters into the floor with angled ties and or huricane ties, the walls can't spread (to quote you) and if that is so the ridge CAN NOT sag. Therefore, why can't you use this method of construction without a ridge beam, even for a cathedral space?
When you talk about the angle ties you were a bit vague. Did you mean nail a 2 by to the side of the rafter and tie it into the floor joist? IF so is this 2x4 stock? do you nail it as low to the floor as possible on the rafter and nail it as low as possible on the floor josit? And how long is the bracing 2x4?
I'm no expert, but a ridge board is different from a ridge beam. A beam is needed only where the rafters are not supported by opposing rafters and/or where you want to keep downward/outward pressure exerted by the rafters from pushing out an otherwise unrestrained wall segment. Ridge beams are designed to remove the outward lateral forces exerted by rafter ends. Ridge boards are useless for this. Heck, I've seen roofs without ridge boards or beams -- just rafters nailed together at the tops and held in place by the decking. Unless you have a triangle with all three legs intact, you probably need a beam. Collar ties are in the upper 1/3 of the rafter spans; rafter ties are in the lower 1/3. Both act as the bottom leg of a triangle. If your floor joists securly connect the bottoms of the two legs of the triangle formed by opposing rafters, you MAY not need either rafter ties or collar ties. I say "may" because these components do serve to add rigidity to the roof structure other than just preventing spreading at the base. They make an intermediate triangle that adds stiffness to the roof deck and resists the effects of wind lifting. The length of the rafters is an important consideration for this. An architect or engineer should determine if either of these components are required.
When undergoing a recent inspection, I pointed out to the inspector the lack of collar ties on a hip roof on an addition, saying that I knew I needed to add them per code, but just hadn't gotten around to it yet. He said "don't bother -- your floor joists are enough." The archi disagreed though, and I'll put 'em in regardless of the inspector's assessment.
Mike HennessyPittsburgh, PA
Mike, Thanks. I basically knew/know all of which you spoke with the exception of the collar vs rafter tie terminology. And as for that terminology, I will very likely forget it in ten or fifteen minutes. Just no good way to trick the mind to remember that one.
Your post is all good and fine, but general. I realize it is difficult to be definitive as to when a ridge beam is necessary and when it is not, as there are alot of variables include, One I would guess, snow loads.
As such I was asking the two posters here to discuss teh specific technics used and under what conditions. Still would like to hear there input to my questions.
woodguy99, When you build a roof system where the rafters come down to rest on a "raised hell" (just assume it is a 2 x 6 on the flat, nailed to the second floor floor) do you still use a ridge beam? And do you use any special hardware to tie the rafters to teh raised heel?
It really depends on the situation. One addition I designed that another contractor is building has a 10-pitch roof supported with ridge beams. The 2x10 rafters are toenailed to 2x6 plates and are tied back to the floor joists with angled 2x4 struts.
The house I will start framing this week, which I didn't design, is a gambrel roof with 2x10 rafters sitting on a 2x6 plate. The lower pitch is 25:12 so there's not much outward force; we'll be using some sort of Simpson clips (forget the item#) but that's it. There are several dormers which will sit on the floor system and act as shear panels as well.
Mike Maines
if indeed you are speaking of a ridge BEAM a 2by won't do the job more than a few feet.
An engineered size for the span and load comes in all sizes, but it has to be planned for the job. Not just any old LVL or glulam will do.
But if you mean a ridge BOARD instead, all you need is for a nailer to balance out opposing rafters and a 3/4" board will do it.
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