I am building a workshop that is 20′ x 30′. I was planning on using 2x12x20′ Douglass Fir at 12″ on center for the joists for the second floor. The problem I have is that no one in my area carries Douglass Fir of that size. One place had Spruce, another has “framing lumber”.
Do I need to worry about the difference between grade of lumber or will Spruce or “framing lumber” still work?
You can see the plans at: http://www.theworkshopproject.com/plans.php
Thanks in advace.
JPS
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Replies
Our building code has span tables for various types of wood. I suspect yours does too. Spruce, while nicer to work with, is significantly weaker. A 20' span is pretty big. Have you considered TJI's?
Scott.
Scott -I was waiting for that question. :-) I'm assuming TJI's are engineered joists.I considered them, but ruled them out, because of the extra work involved in tying them to the rafters. I was planning on nailing the rafters to the joists so that I wouldn't need collar ties. This leaves me more headroom.Being that I am a homeowner and not a pro, I don't know if there is a way to directly tie an engineered joist to a rafter. Is there a way? If so, I might consider engineered joists.JPS
I see in your plans that your floor joists are acting as ties for your rafters, and that the rafters are also specified as doug fir.
Where are you? West of the Rockies, doug fir should be readily available, but in the east, it is not easy to find framing lumber in this species. I am in upstate NY, and only one of my lumber suppliers has doug fir, and what they have is appearance grade. It is quite expensive, maybe 5 times the price of "framing lumber."
From what I see, your entire shop can be built with #2 SPF framing lumber. SPF means "spruce-pine-fir" and a supplier selling it might have a mix of species, but all graded and stamped.
SYP (southern yellow pine) framing is the species generally found in the southern states across through Texas, and your shop can be built in graded and stamped #2 SYP.
I-joists might be a choice for your upper deck, but because of the need to nail the rafters to the joists for the tie connection, you will expend labor and materials to pack out the webs of the joists at the connection, and your I-joist engineer will need to take a look at your design. Sawn lumber will be cheaper than the I-joists.
Stinger -Thanks for the information.I live outside of DC. I wasn't sure about the cost difference between framing lumber, Douglass Fir, and I-Joists, but I assumed they would be more expensive. JPS
I'm with Dieselpig now that attic trusses are suggested.
Take your plan to a lumberyard and get a quote for a truss package with "attic truss" specified. Ask that they provide gable end trusses as well.
If your attic space above this shop is for light occasional storage, meaning no heavy loads, and just occasional access, consider trussing the whole thing on 24" centers stacked above your wall studs below, and use a folding attic ladder for access.
If you need access wider than the 22-1/2" you'll get between two trusses with an attic ladder, then you'll have to stickframe four feet of your roof and floorframe, and probably post down to the floor below for bearing.
Regarding the 3/8 sheathing on the roof, it might be OK although others here are saying no. Just ask someone at the lumberyard that handles pro builder accounts, how much 3/8 he's selling to the builders for roof sheathing. Those of us in snow country never see roof sheathing that thin, but you aren't in the kind of roof snow load territory we are.
May we presume you are going to build it yourself, with a little help from a couple friends now and then?
May we presume you are going to build it yourself, with a little help from a couple friends now and then?
Stinger -
You are correct. I am framing the shop myself. I get a hand here and there from some friends or family, but I can't always rely on people to be there. Sometimes schedules just don't mesh.
As for the trusses, I looked into them, but the cost is higher then framing, plus I am already going to have a bear of a time getting the 2x12 stock up there let alone a roof truss.
JPS
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http://www.theworkshopproject.com
"I wasn't sure about the cost difference between framing lumber, Douglass Fir, and I-Joists, but I assumed they would be more expensive."What's "Framing Lumber" mean?Every house or addition I frame we use "Doug Fir" but I've never heard "Framing Lumber" used before as opposed to any other lumber before.Joe Carola
We spec DF here too, but I believe it is Hem- Fir and mixed.
EricIt's Never Too Late To Become
What You Might Have Been
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What's "Framing Lumber" mean?
Framer -
I think "framing lumber" is SPF, or Spruce-Pine-Fir. Since I am in the mid-atlantic (D.C.) that is mostly going to be pine.
JPS
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http://www.theworkshopproject.com
I'm not a pro, but is 3/8" OSB going to work for roof decking @ 24" O.C. ?
Seems like in past discussions, people have favored 1/2" with clips or 5/8".
r- Good question. I'm assuming that 3/8" for roof decking is fine since the engineer at the permit office OK'd it. She made me up the rafters to from 8" to 10" and my joists from 24" O.C. to 12" O.C.JPS
Whoah....made me up the rafters to from 8" to 10" and my joists from 24" O.C. to 12" O.C.......thats a considerable amount of upgrading in an effort to accomodate 3/8" OSB.
Any reason you don`t go with a plywood deck instead?
Lemme get this straight....
YOU BANNED REZ?!?!
Holy bagels and lox Batman!
Any reason you don`t go with a plywood deck instead?
JDHRI -
OSB is cheaper. I don't think they upped the rafter and joist size to accomodate the decking. I think that was an engineering calculation... or something. To be honest, I'm not really sure. I was just so stressed about getting the permit that I didn't want to question the engineer too much.
JPS
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http://www.theworkshopproject.com
You should find out.
While the rafter sizing may not have been changed to accomadate the OSB, its possible (likely even) that the spacing was changed for this reason.
If using OSB to save money is your goal, doubling the number of rafters needed isnt going to save you anything.
As others have mentioned....16" centers should be fine for a 1/2" plywood deck. You can do the cost calculations for yourself.....but even if this suggestion ends up costing the same as what the engineer has approved, it will be a superior finished product.
FWIW.....A house is first and foremost a means of shelter. The roof being literally the pinacle of that shelter, I`d look to save dollars elsewhere.
Best of luck to ya!
Lemme get this straight....
YOU BANNED REZ?!?!
Holy bagels and lox Batman!
"ood question. I'm assuming that 3/8" for roof decking is fine since the engineer at the permit office OK'd it. She made me up the rafters to from 8" to 10" and my joists from 24" O.C. to 12" O.C."She's WRONG!Don't even think about putting 3/8" sheathing on your roof. This Engineer wants you to put your rafters 12" centers also?Is that to keep the 3/8 sheathing from sagging in between the rafters?Why not just go with 2x10's @ 16" centers with 1/2" or 5/8" sheathing. She's costing you more money for 12" centers with garbage 3/8" sheathing to nail roofing into. I don't get it...........I seen 3/8" on a roof once about 15 years ago on 16" centers. The whole street had it and you could see it a mile away all the sagging in between the rafters. I has to rio the roof off and it was a joke.Just because there might be other houses that have it doesn't make it right or look good. So do yourself a favor and go for at least 1/2".When I first starting framing all we ever used was 1/2" on the roof but now we use 5/8" with rafters at 16" centers. Joe Carola
You are right about the sag if using 3/8" OSB. But he might be OK with what little sag might occur on his roof, which has a nice steep pitch.
I still think he might be best off, for this workshop building roof, to use 2x4 purlins on 24 centers and roof it in something like Fabral GrandRib steel. No valleys, no hips, it would be an easy day doing it, and he would be done with roofing for a long time.
I've seen 3/8" over 16" o.c. on some Habitat houses in Long Beach, CA. Never saw the finished product, so I can't say how well it worked. I agree that it's really pushing the lower limits of the envelope on how you build the envelope.
-- J.S.
My opinions are:2X12s spanning 20' are overspanned. I wouldn't do it, regardless of the spacing. Using 3/8" ply for the roof would be a big mistake. I wouldn't do that either. Attic trusses will work. They would be less labor, but more expensive. Deeper I-joists would work for the floor also. Most manufacturers show situations like this in their literature.
Work: It isn't just for sleeping anymore.
I don't know where you are, but here in MA, doug fir isn't available either. For sticks longer than 18' we use hem-fir as SPF isn't usually available in longer lengths and can't handle the same loads. We can get hem fir from 2x6 to 2x12 in lengths up to 28' without special ordering. Maybe that's available near you?
Also, yes, you can nail your rafters to the side of I-joists without any special hardware in most situations. Just be careful that the plane of your roof won't force you to 'clip' the top of the I joists beyond acceptable limits. (in other words... RTFM) ;) I'd use I-joists if I wanted a decent floor up in that attic, but if I was looking at using the space for light storage, I'd probably go with conventional lumber or even attic trusses.
Also, just a pet peeve of mine, but the framing member you are trying to eliminate by nailing your rafters to your joists isn't a collar tie. Your floor joists will serve as your wall ties, but you will still need collar ties in the upper third no matter how your frame the roof. Wall ties fall in the lower third of the rafter span and prevent the walls from spreading. The can be eliminated by using a ridge beam instead of a ridge board, but in your situation the floor/ceiling joists will serve this purpose.
Also.... skip that 3/8" OSB roof sheathing. Use 1/2" at a minimum, but 5/8" would be my first choice. Especially at 24" oc.
"but 5/8" would be my first choice."
Thats what I used.
I also built with SYP it is more $$ but in the big picture it wasn't extremely more $$ and the availability of boards was superb.
But I am in the south-----------------------------------------------------------------------------
WWPD
First off, You really need to find out what species and grade "framing lumber" is.
SPF has longer spans than DF-South.
There must be some local wood that is suitable.
I found an online calculator from the American Wood Council that allows you to input your requirements, and it will spit out what size/span you need. Pretty cool.
Maximum Span Calculator for Joists & Rafters
Span Options Calculator for Joists & Rafters
JPS
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http://www.theworkshopproject.com
The one I use showed #2 SPF 2x12s maxed at 19-11 for a "sleeping rooms" loading of 30 psf live and 10 psf dead. That was on 16" centers, and would work for you, because the span is measured from insides of bearings. 20 feet overall on 2x6 plated walls yields a span of 19-1.
That would work for you except that you need to tie your rafters, which are on 24" centers, to the floor joists. So it looks as if you will have quite an attic floor at 12" centered 2x12s, especially since you are only flooring the stand-up space, and not going out to the walls.
Did you ask a lumberyard guy about 3/8" roof sheathing? Is 3/8" square edge OSB actually available to you? Does Simpson make sheathing clips for 3/8" thickness? Are builders around you using 3/8? If the answers are all yes, then you'll be OK with it.
Edit: I just went to Simpson's site, and they have 3/8" clips. I went to another site re OSB roof sheathing, and the maximum span 3/8" can handle with edges supported by clips is 24" centers. It looks as if you have light roofing (28 gage steel would be good) and a very low snow loading, you will be OK. Actually, with a steel roof, you can forego sheathing it and instead strap it with 2x4s.
Edited 10/26/2005 10:37 am ET by Stinger
Nice job on the plans
I'm not too familiar with sheathing under metal roofs but I'm feeling skeptical about 3/8 osb. I'd be skeptical about 1/2 osb @ 24"oc but thats my prejudice. I'm posing this question for those more experienced in this area?
Tom
How much money are you going to save by using the 3/8 sheathing? Do you plan on being there any length of time? Spend an extra couple of bucks and put something worthwhile on the roof.
If you ever walked roofs with 3/4 and 1/2", you would know the difference. And you want to go to 3/8"? You can go through that stuff way too easy. (Let your skinny friends help do the roofing.) Granted, the 12" rafters will help, but somewhere down the road, like when the next roof is going on, I'll bet they cuss you out.
Good luck with the project.
Don K.
EJG Homes Renovations - New Construction - Rentals
All right. I'm sold. I'll go for the 1/2" sheathing. 1/2" can't be that much more.JPS
I can hardly see them, but, by en large, I find the format of those plans highly unusual.
I live in NC, but used to live in No VA. To keep with standard methods and materials I'd use I-joists for the 2nd floor and use 2x8s, on 16" centers for rafters. I'd also use 7/16" OSB for the roof sheathing.
Depending on what you intend to use the 2nd floor for (living space or storage) and also depending on if there are going to be stairs going up there, as an alternate plan I'd use roof trusses set up as storage trusses.
Another plan would have been to use open web floor trusses.
For the I-joists or floor trusses you would have probably built the 2nd floor floor system and then put one or two 2x4 plates around the perimeter and then set you rafter birds mouths on top of that, meaning the sides of the 2nd floor system would have made up the upper portion of your side walls (at the eaves).
Any builder or framer in your area could have told you that 20' joists made of conventional lumber was questionable at best. Also, around here anyway, stick framed roofs are normally - like 95% of the time - done on 16" centers.
Depending on a plans reviewer for building advice is not the best idea as is evident by the fact that she approved a plan using material (DF) that is not commonly available. Who is to say that that person has ever built anything in their life - or are they just someone with a thorough knowledge of the building code and also knows how to look stuff up in span tables, etc. Maybe the plans reviewer will give you your money back and give you another chance ;-)
All that's hind sight now...
You are kind of hosed because you have an approved plan set (and I gather a partially done project) and now can't get the material that has been approved. Are you sure you can't go to a real lumber yard and order the DF for the floor? The place that told you they sold "framing lumber" is not a real lumber yard - was that HD or Lowes? Either that or use SYP - that should be readily available - although possibly special order.
Using conventional lumber is gonna be kind of "bouncy" though. For a ~20' span L360 allows 2/3" of deflection.
Also - use 7/16" OSB on the roof with H-clips.
To wrap up this thread. I went with the SPF joists, 12" O.C. I started putting them up this past weekend:
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See more of the photos
JPS