Floor Joists and Rafters - I-Joists, Truss Joists, Other?

mcbane said:

1) Dont buy from a big orange store, because they will load up the last two years worth of discarded, twisted wood that resulted as every other customer picked through the pile looking for straight boards
2) If you must buy from a big orange store, order 16 ft or longer, even if you will just be cutting it down. Usually it is the 8 ft and 10 ft lumber that gets the severe picking through, since most customers dont have lumber racks and are unable to carry the longer stuff home.

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I definitely agree with all of that! I have never bought a single piece of lumber from our local Big Box stores that I didn't have to dig for and the last time I had lumber delivered from Lowes I had to have about half of it sent back. GARRRRRBAGE!

I'm going to check out 84 Lumber this time. Never bought from them, but have heard good things about our local 84. We also have a Mom & Pop store right in town that some people swear by because of their quality. Slightly more, but I'm going to have them quote everything. They carry a lot of engineered lumber and may even put my BIG LVL beam in place for me for a bit more. Knowing the owner might work in my favor as well.

ssdave said:

I built a garage with loft woodworking shop like you describe, and used all I joists. Your span for the I joist floor is trivial for that application, they will work easily. You don't need to go to trusses, just use cheaper I joists and they take up less height. The advantage of trusses is they have more room for HVAC and plumbing in houses and can be spaced at 24" o.c.. If you don't need that, I joists are generally preferred. I think 9" ones 16" O.C. will be right, check the span table. I'd consider using 1 1/8" T&G OSB on the floor instead of 3/4". It has a lot less flex and bounce than 3/4", and cost isn't enough more to be prohibitive.

The rafters are a bit more of a question. i used 9 inch I joists, but framing details get a bit challenging. You have to cut spacer blocks and attach to let you use joist hangers and other framing ties. Blocking is a bit harder to do. The hangers at the top that go on the ridge beam are expensive. Hurricane clips are difficult to attach and need spacers. Overall, it was a pain to do. I'd pay to get select #1 rafters before I did that again. Another way to go might be to go with engineered LSL or LVL rafters. They are perfectly straight, but expensive. Once you take into account the work of using I joists for rafters, it might be worth it. Overall, sawn lumber looks the best in an open beam ceiling and is easiest to work with. And, it is the least expensive option. Just take the time to select the quality you need, even if you have to pay a bit more for the pick privilege.

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I totally agree with the cut lumber looking the best and with the other features of the roof that will be there (2-dormers and a partial tower), the cuts would be far more complicated and a ton of blocking. I will have to have the majority of the structure built in a week, so construction speed will be a consideration. That's great input! Thank you!

theoldwizard1 said:

2 quick comments.

Make sure your joist sit on top of the wall like in your picture.
Use construction adhesive and screws to secure the floor to the joists.

Want more information on engineered floor joist? Feel free to contact us.

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Absolutely agree!!

ducatithunder said:

I just did this with my garage. I wanted the clear span for 28' and it had to handle a snowload for my area in MD and a 1/12 pitch. No beam in the middle to support the roof. I went with nordic truss NI-40X I-joist in the 14 inch version. My building has a 3 ft overhang on the front with 2 ft around the other sides. I put them on 12" OC on 12ft and 14ft load bearing walls. My local lumber supply ordered them directly from nordic with a week turn around, straight from the manufacturer in 40 ft lengths that I was able to field cut down. Very little wastage. All in it was about $ for the material. I would use I joist again as it was a very easy and straight forward process. When we lifted them into place I had a man lift on the front and rear of the building. Each finished joist was about easy enough for 2 guys to move and lift into place. When the roof sheathing was place they were stable as a rock.

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That is fantastic information!! Thank you!

kasander said:

Sounds similar to my garage. I used floor joists because I am running HVAC, electrical, plumbing for the upstairs portion. My intention is a 1BR apartment upstairs. I also have head and sink downstairs in garage. I wanted to minimize overall height of my garage so I requested 14" tall trusses supported by a beam midpsan of my 26" width. Beam is nested up in the trusses so that it doesn't stick down into the garage very far. It is very roomy upstairs with the front and rear dormers. I designed this and passed to an engineer to size the beams and trusses. Original design was 12/12 roof, but I modified to 10/12 to reduce overall height. I still have 9' ceiling height upstairs.

If I could do over, I would have used 18" trusses so the beam would not protrude down into the garage, and HVAC ducts would have fit better.

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Now these are some additional great points. Something I'm on the fence about and wouldn't do until a bit down the road would be HVAC. I think any plumbing I do will be downstairs and plan to at least set some plumbing during the foundation build to make sure I have provisions for a toilet or even just a sink. BUT! HVAC is something I may need to think more about. Floor Trusses are definitely better for running HVAC. I will have 10 foot ceilings in this building, so it may be a non-issue, but it's on my mind. I would also probably consider mini-split systems as well and divide up the upstairs and downstairs work areas.

Reducing my pitch to 10-12 is also something I'm thinking about. Out house is 12-12 and wanted to match it, but the building will be set back to the rear of our property and the pitch would be faced away from view, so I may never even really notice the difference. We're trying to match the architecture of the house as best as possible because of it's historical value. Would also take just a bit of cost out of structure at the end of the day. I'm going to draw it up both ways and see how much space I really lose. It would be REALLY tall with a 12-12 pitch and that's something that has crossed my mind. OH! And roofers charge an up-charge around here for anything over 10-12, so there's that point, as well.

GREAT stuff! Thank you!

You guys are FAST! Wow! GREAT feedback!! Some great looking builds, also!! Keep the input coming.I definitely agree with all of that! I have never bought a single piece of lumber from our local Big Box stores that I didn't have to dig for and the last time I had lumber delivered from Lowes I had to have about half of it sent back. GARRRRRBAGE!I'm going to check out 84 Lumber this time. Never bought from them, but have heard good things about our local 84. We also have a Mom & Pop store right in town that some people swear by because of their quality. Slightly more, but I'm going to have them quote everything. They carry a lot of engineered lumber and may even put my BIG LVL beam in place for me for a bit more. Knowing the owner might work in my favor as well.I totally agree with the cut lumber looking the best and with the other features of the roof that will be there (2-dormers and a partial tower), the cuts would be far more complicated and a ton of blocking. I will have to have the majority of the structure built in a week, so construction speed will be a consideration. That's great input! Thank you!Absolutely agree!!That is fantastic information!! Thank you!Now these are some additional great points. Something I'm on the fence about and wouldn't do until a bit down the road would be HVAC. I think any plumbing I do will be downstairs and plan to at least set some plumbing during the foundation build to make sure I have provisions for a toilet or even just a sink. BUT! HVAC is something I may need to think more about. Floor Trusses are definitely better for running HVAC. I will have 10 foot ceilings in this building, so it may be a non-issue, but it's on my mind. I would also probably consider mini-split systems as well and divide up the upstairs and downstairs work areas.Reducing my pitch to 10-12 is also something I'm thinking about. Out house is 12-12 and wanted to match it, but the building will be set back to the rear of our property and the pitch would be faced away from view, so I may never even really notice the difference. We're trying to match the architecture of the house as best as possible because of it's historical value. Would also take just a bit of cost out of structure at the end of the day. I'm going to draw it up both ways and see how much space I really lose. It would be REALLY tall with a 12-12 pitch and that's something that has crossed my mind. OH! And roofers charge an up-charge around here for anything over 10-12, so there's that point, as well.GREAT stuff! Thank you!

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