Roof Trusses

[Mark Kelly]

Here is a quick scetch of a roof truss. Inside the circle is a gap to show how the cut angle is supposed to be. Now, when I was building these this weekend, I had a problem where the bottom horizontal board was warped like shown in the picture. If it is hard to tell, it is bowed on the sides, not the face and the ends are a little lower than the middle. This warping caused the angles NOT to match.

What is the best way to fix this problem? I run the risk of not making all the trusses the same (making nine total)

[Mark Rios]

When cutting a roof (I learned to cut roofs 20 some years aog), whether it was cut and stack or building trusses, I've found that it just won't pay to use anything but good, straight, sound material. Problems will continue to show up, both inside on the finished surfaces (level, flat ceiling, cabinet installation, crown moulding, etc.) and on the outside (wavy rafter tails/eaves, wavy roof deck, etc.). Sorry, but I have to recommend that you get some material to replace any non-straight, unsound material that you have. Just my opinion.

[Michael Cody]

I've built a fair number of trusses & other roof structures in my life. I am not a pro so the Addy Protocol does apply.. but in roofing, if it ain't straight - I don't use it! Mark is dead on. All you will get is more problems.. I believe that professional truss builders actually clamp them straight and when all the tuss components are attached, the truss comes out straight, but they don't always stay that way as any good plaster guy will tell you right quick.

[Wes Bischel]

I would have to agree with Mark. Get good straight wood and use the warped stuff in small pieces for blocking etc. I have seen people spend hours trying to work around a warped piece and it really isn't worth it. My dad was a stickler for getting good lumber - we culled out anything that even looked like it would warp at the beginning of a job to use for deadmen, blocking etc. It really does make the job go smoother.

FWIW
Wes

[Rob Russell]

The first thing to me is the design of the truss. If you're planning to nail the roof joists into the edge of the bottom stretcher, I think you're in danger of the truss failing. I believe you want the elements to overlap as shown in my quick diagram and pin it sideways. That way your nails are holding the truss together based on the shear strength of the nails, not the pullout power of the nail.

Maybe I'm interpreting your design incorrectly - if I am, please holler.

Rob

[Mark Kelly]

Yes, I didn't give the whole story. The joists and stretchers will be attached via 1/2" plywood gussets on both sides...with construction adhesive and nails. I was trying to show where I do have a gap because of the warped piece of wood.

And after reading all the above, I realize, yes, that I need new stretchers and I think a few rafters. I was wondering if that was the solution, but since this is my first real "framing" project I didn't know.

[Rob Russell]

Yes, I didn't give the whole story. The joists and stretchers will be attached via 1/2" plywood gussets on both sides...with construction adhesive and nails. I was trying to show where I do have a gap because of the warped piece of wood.

And after reading all the above, I realize, yes, that I need new stretchers and I think a few rafters. I was wondering if that was the solution, but since this is my first real "framing" project I didn't know.

Is there are reason you're using gussets and introducing all that extra precision into your construction?

Why not build the truss as I showed? You eliminate a lot of the mechanical fastening and transfer the load directly from the roof joists to the stretcher rather than using plywood as the transfer mechanism. Easier to build too - your stretcher just needs to be trimmed so it doesn't stick out/up past your joist.

Just my .02 ...

Rob

[Mark Kelly]

Yes! I am using this design cause that's what the plans say! I told you, this is my first framing project and I have NO experience in framing. I have read a book and bought some plans and going from there.

To tell you the truth, your design actually appears weaker than the one I am using. But, like I said, I don't really know since I have never even seen your design. It seems that if the roof joists are directly on the stretchers which are directly over the wall studs that it would give you the best strength overall. The wall studs are 24" OC if that makes any difference.

Wouldn't your design put too much weight on the nails to hold the trusses together? I assume the rafters are nailed to the side of the stretcher, right?

[Mark Rios]

Mark, After reading your responses to some of the replies that have been posted, I would like to respectfully suggest that you read a book or two more on roof structure and construction and/or have a custom home builder in your area give your some pointers and advice.

I just reread your oringial post. You are only building nine trusses; Is this for some sort of outbuilding, i.e. a shed or work shop? At 24" o.c. (on center) that sounds like a 16" deep building.

Rob's drawing, I'm sure, is just a quick drawing to give you another idea for roof construction. Actually the rafter in his drawing would have a birdsmouth cut out of it and it would sit on the wall and nail up next to and into the roof/ceiling joist. This connection (or intersection) of material would sit directly over each stud an a wall layout of 24" o.c. If your walls were on a 16" o.c. layout the rafter/joist connection would be able to set on the double top plate of the wall and the roof weight would be carried just fine. Depending on your local codes, I see that you are in New Mexico, there might also be some Simpson hardware required to help tie the roof framing to the wall framing.

As for your truss construction plans, I would also suggest that your continue to follow them VERY carefully, as it sounds like you are, and be very diligent about using good sound materials and all of the recommended hardware and glue products. The plans that you have probably outline some sort of nailing/screwing pattern and maybe even some sort of a gluing pattern as well. Try to follow those instructions to the letter.

Keep on asking questions as you need to and even drop me an email if you would like and we can talk further. I'd be glad to help. It sounds like your having a good time with a fun project.

[Mark Kelly]

yes, this is an outbuilding and it is 16' by 12'.

Oh yes, I am following the plan. I don't want to deviate from it at all, other than moving a window from one wall to another. Unfortunately, there is no diagram on a nailing/gluing pattern. It says to use construction adhesive. My guess is liquid nails construction adhesive. I hope that is good enough.

By the way, my problem with most of this stuff is terminology. Some call it different things and I get confused since I am not really sure what the exact termonilogy is.

Yes, am having a great time doing this project...until I run into one of these situations! Then it isn't fun, because I don't know where to turn.

Thanks for the invite to email you. I may do just that after I go and see just how many stretchers (ceiling joists?) I have to replace with straighter wood.

[Mark Rios]

Mark, the terminology can be very important to the outcome of the project, as you're finding out. Please don't hesitate to email with any question you might have.

The Liquid Nails will probably be okay as long as it's not too old. It shouldn't be starting to get stiff in the tube. Sometimes the product sets on the store shelf too long in my opinion. Actually, construction adhesive is a little different animal, a separate product. You should be fine though unkess an official is actually going to want to see what you used for an adhesive. In that case you would look for "sub-floor adhesive". It comes in the regular size tubes, probably like you're using and it also comes in a giant tube that is used on the jobsite.

The idea on the nailing/screwing pattern is not to get too many fasteners in a line in the same grain, creating the potential for a split. You want to look carefully at the grain that you are nailing/screwing into and try to stagger the fasteners so that they don't exactly line up in the same grain.

Hope this helps.

[Michael Perata]

Mark

The "bow" you are experiencing is called the crown when a plank is used as a rafter or joist. It is normal (1/2" in 12' feet would be ok, 1/4" better) and should be at the top of the joist or rafter.

The "crown" will collapse out when you hang drywall.

[Mark Kelly]

Here is the followup. Turned out that 4 of the boards were too badly warped for use. So, those were replaced with new ones and what a difference that made. All of those problems mentioned above just went away. It sure felt good when everything started fitting. I do appreciate all the help. I learned a lot just from this problem.

On to building...

[Chris Padilla]

Hey Mark!

How about some pics!? Pics go a long way to helping to explain things and getting you quick answers. Besides, we LOVE pics! :D Glad SMC came to your rescue...we're here for you! :D :D

[Mark Kelly]

Ok, I'll remember that. I will post some pics when I am finished. It'll look better then anyway. :)