loft joist question

[jdhen]

I have a question for John or any of the resident experts on the forum.  I'm working on
modifying the Builders cottage plans, keeping it 14 ft wide but extending it to 34 ft long
with 10 ft sidewalls.  I plan on using the 2x6 let-in ledger to support the loft joists.  The
loft will extend the entire length of the building.
My question is this:  If I frame the walls on 16 inch centers (as I know you all prefer)
and I place loft joists on 32 inch centers so that each one matches up with with
a wall member what size joist would be required? I was hoping to use 2x8 joists but would I
have to keep the loft joists on 16 inch centers if I did that? For the loft floor I plan to
use 2x6 tongue and groove decking. Visually, I would prefer to have a wider spacing on the loft
joists so the decking can show through.
The plan lists 4x8 on 48 in centers which I may do but I was wondering what some of the other options would be.
Thanks.

[MountainDon]

The AWC calculator comes up with a max span of 13'6" for 2x8 SPF #2, on 16" centers using a deflection of L/360 and 30 lbs live load. So changing that to 32" OC would not work with that material.

Remember span is measured from the inside face of the supports. A 14' wide with 2x6 wall studs would have an approx 13'1" span.

[John_M]

Can you find someone in the area that can get you some solid beams that measure 4 x8 for you.  The built up beams will do and you can box them in...but I think the entire 4 x 8 beam cut out of solid lumber kind of goes with the T & G flooring you mention.  I found an Amish Mill near me that was able to make me 4 x 12 hemlock beams.  It was well worth the hassle!!

Here is what mine looks like:

[jdhen]

Those beams look great, John.  I guess I just thought it would cost so much more for such large dimension lumber.  There is a sawmill not far from the property we are closing on so I'll have to look into it. 
From the pictures on your site it appears you started the beams at about 32" in from the end wall.  Is there some sort of ledger board attached to the the endwall to support the ends of the decking?

Mountain Don- The AWC chart doesn't have any options for spacing over 24 in on center.  Is that because any size of 2x is not recommended anything larger than 24 o/c?

I guess if I went with beams the let-in ledger would be insufficient and I should use cripples instead?

[John_M]

the flooring is a little closer than that...I think it is actually like 22 or 24 inches.  But to answer your question, he do kind of rest on some 2 x 6's that sort of act as fire blocking.  It is really a low traffic area and they are T & G so they lock in together.

Find the beams if you can...I think you'll be happier!

[Don_P]

A quick and easy way for most applications would be to use the allowable span for 16" and double the member width if doubling the spacing. Using Mountain Don's info of a 2x8 being acceptable for the span at 16" spacing means that a 4x8 beam of the same species and grade will work at 32" spacing. The flooring has to be able to handle the 28-1/2" span between joists. This method does not work on heavy timber above 5" thick though. Some terms, 2-4" thick is referred to as "dimensional lumber", 5x and thicker is termed "heavy timber". Heavy timber carries lower allowable design values because we know less about what's inside and it carries more load per member.

I checked it in #2 SPF lumber @32" on center, a 2x10 worked.

If you want to run the calc I made this one for doing this type of work, it uses the code referenced math, I suck at long strings of calculations so I stuck it in a javascript program;
http://www.windyhilllogworks.com/Calcs/beamcalc.htm
inputs were
Load-1183
span-133
width-1.5
depth-9.25
Fb-962
E-1.4
Fv-135
Click "Show Result"

The ledgers are carrying half the load each, 591.5 lbs. SPF has a side grain allowable crush strength of 425 lbs per square inch. 591/425=1.39" square inches bearing area needed minimum. A 2x joist on a 2x ledger is 1.5x1.5=2.25 square inches, we check out bearing on a ledger.

I can walk you through any part of that or joist options if it is of interest.

One thing to remember joist strength is very dependent on the grade of lumber used. The building code specifies that structural lumber is to be graded by a certified lumber grader. Small mills do not have graders but some inspectors and some states don't enforce this. Do keep in mind that the laws of physics are generally unbreakable though, even if you are not required to have the joists graded do use good judgement. Calling a beam a number one when its actually a number 4 is not going to keep it from failing (I do have the same complaint with the official graders BTW, their stuff still has to pass my grading no matter what the ink says) Just be safe with ungraded if you are allowed to use sawmill wood.

I like the 4x option if it is possible.

[jdhen]

Thanks, Don.  That is very helpful information.  I called a local lumber company and got a quote for rough sawn, real dimension cedar 16ft, 4x8 beams for $97.35.  Not having investigated this before, does this sound like a reasonable price?

Also, you mentioned the 2x ledger.  The plans call for a let-in 2x10 band joist but every discussion I've read on the forum always talks about 2x4 or 2x6.  Is that because most are using 2x joists instead of the 4x beams and the 4x requires the 2x10?  This likely makes sense to everyone else but since it's new to me this stuff is sinking in a bit slower 
If this is the case, I wonder if using 2x6 cripples is easier since I only need to support 8 beams in my plan.
Thanks to all for the help.
Jesse

[John_M]

My 4 x 12 beams (which were cut at 4.5 x 12.5 and then planed down) were 18 feet long and cost me about $56.00 each or so.  They were hemlock.  So the price is a little high..but they're cedar?  Not sure on the strength of cedar....others have more knowledge on that.

I used cripples to hold up the beams because some of them rested on some of the headers and it was harder for me to figure it out.  Jus tmy personal choice I guess! 

[Don_P]

Cripples is certainly stronger, John will have to speak to the ledger dimension  I go for strength if all else is equal, here the other factors might be insulation and cost.

A contractor i'm going to be helping here shortly told me he got a price on some WRCedar 1x4's this morning that was $3/board foot, we about...umm never mind. At (4x8x192)/144 there's 42.66 bf per joist so he's charging $2.28/bf. WRC would not be my first choice for a joist or beam it is not particularly strong or stiff and can have bad knots all depending. It is stable and relatively decay resistant so it makes good siding and trim or log home logs. Sized and graded appropriately you can use balsa wood for joists, they might need to be 8' thick though. Plug these design strengths in, I think it'll take more than a 4x8.. If its #2 or better WRC, Fb=770, E=1, Fv=155. If its ungraded I'd be suspicious of even those numbers. Don't buy a pig in a poke, see what you're getting if at all possible.

Notice John paid .66/bf for the hemlock, which is a lower dollar value wood. It is weaker in bending but stiffer than cedar but he got twice the beam you were quoted so is stronger. Hemlock tends to have shake but is fine wood when it doesn't. Generally if wood smells like cat pee it has a bacterial infection that leads to what the old timers call "wind shake", a seperation between growth rings that can cause wood to fall apart. I see none in John's, just trying to think ahead and rambling. I've got some yellow poplar here that I'm selling for .60/bf but poplar checks badly if sawn into timbers so I milled it into 1 and 2" thick lumber. A couple of folks have told me they think that is too high but I know what I've got in it so there it is from my end. I'm guessing John and I are east coast and I'm not sure of your location but if you're not west coast the WRC has alot of fuel tied into it's cost. We are quoting mill price for green timbers, you are quoting dealer price and I don't know if green or dry, drying takes energy or time, both have a cost, dryer is better, less shrinkage and suprises. WRC is also a fairly high demand tree that spotted owls also like to hang out in so it has a number of things contributing to its higher cost.

In general (you know how safe that is) softwoods tend to be weaker but move less while drying and are easier to handle than hardwoods, which are stronger but tend to twist and check more and are harder to machine and connect to, but those connections are stronger. If the washing don't get you, the rinsin sure will 

The primary spanning wood in the east is SYP, southern yellow pine, out west it is DF, douglas fir. They have closer to hardwood strength but closer to softwood stability. 

Hopefully I didn't just turn that into a mud puddle 

[MountainDon]

The primary spanning wood in the east is SYP, southern yellow pine, out west it is DF, douglas fir. They have closer to hardwood strength but closer to softwood stability. 

FWIW, here (NM) the primary 2X spanning wood is Hem-Fir. DF is available usually only in 4X material (S4S).

Hem-Fir is a species combination of Western Hemlock and the true firs (Noble, California Red, Grand, Pacific Silver and White fir). With strength properties slightly below DF-L (and above DF-S),

[jdhen]

I spoke to another lumber supply company and they quoted me $86 for 14 ft #1 rough cut DF .  I only need 8 of them so I think this might be the way to go. 
Don P.- he said the same thing about the cedar- not a good choice for horizontal beams. I would love to use southern pine as I'm in Northwest Arkansas and it would be best to use something more local but he told me that the pine industry is built around the 2x market and he thought it would be hard to get 4x.
Thanks for all the input.

[John Raabe]

That rough cut DF should work fine. Stay away from cedar for structural uses. Makes great totem poles though. 

[jdhen]

John R.- Now that I've settled on the beams I have a question about supporting it.
I know the let-in ledger has been discussed here ad nauseam but I can't find any evidence to explain my question.
I have the builders cottage large sheet plans which I'm modifying to 10 ft sidewalls.
The detail on E-4 shows a 2x10 band joist with the 8" beams suspended by hangers.
Most other examples in the gallery and on the forum are using 2x6 ledger with the beams over and resting on it.
Is there something unique about this application that a 2x10 and hangers should be used or can I modify the detail using the 2x6 ledger?  If so do I then use lag screws to connect the beam to the 2x6 wall stud?  And what would be the appropriate pattern for the lag screws?
Thanks.

[John Raabe]

Using the detail you have in the Enchilada booklet to hang the beams off a let-in ledger will eliminate the lag screws (use hanger hardware). There are other ways to do this such as is done in the 20' wide 1-1/2 story which is most likely what you are seeing on the Gallery. That's a little different - Not necessarily better, just different.

You can also do the built-up posts that John_M showed you earlier.

[rick91351]

This may sound a little weird and just a thought - but did you ask for ruff cut Doug fir or is that the look you want?

The lumber yard I use mostly will special order ruff cut dimensional lumber and beams.   However most times it will cost more than the planed.  And some times a lot more per board foot.  If I want ruff cut I know several people that have sawmills and will custom cut just about anything.  This sounds a lot like what John_M wrote about the Amish mill.

Now assumin' most areas are the sort'a the same.  Check around, there might be some one in the area.  I really don't know how you would find them.  They are most the time not in the yellow pages but word of mouth or the locals know them.  I am not talking like a big production mills but small two three man operations.  They might run when the farming is all done or logging is finished or when they can get a crew together. 

I am surprised you can get pine in dimensional lumber in your area.  Around here framing lumber was all gone to the way of Hemlock-Fir market.  Doug fir is available but at a greater price per thousand.   Our pine is all sawed in to four quarter boards or five and six quarter shop.



             

[jdhen]

Sorry, I don't think I was clear in my post.  
I would prefer to use the other example I was seeing that you say is in the 20' 1-1/2 story (2x6 let-in supporting joist beams which are over and above) instead of the hanger option.   I just wanted to make sure there wasn't another reason that I shouldn't do that.  And I believe you are saying there is not  
So when I do use that option do I use lag screws to connect the beams to the 2x6 wall studs?

Also, I want to lower the ceiling to give more headroom in the loft.  If I put the ledger at 6' 10-1/2 (to set the beam height at 7'4") that's the same height as my door and window headers.  Can the ledger act as one half of the double header with the other 2x6 being supported by the trimmers?
Sorry if this is an obvious question but the framing books I have don't address let-in ledgers.
Thanks.

[jdhen]

Rick,
I didn't ask for rough that's just what he said was available.  Interesting that it costs less to have it planned?   You'd think that would add to the price!
I'll have to double check with the guy who gave me the quote.  I just liked the idea of the rough look so I went with it without thinking.
I think Don P. scared me off of using a small sawmill.  He said that most don't have graders and I have no idea what I should be looking for so I'd rather go with something that has had an experts eyes on it (even though Don admitted that he's not so sure they do a good job either).

[Don_P]

It's partly prejudice, I've taken the training to grade. If you look at stamps and see "TP", the largest grading agency, that's where I trained. The fresh faced business major beside me went on to work for the agency as a check grader overseeing the graders on the line, I can't afford to pay the dues so cannot stamp which code requires. He was a business major with no experience, I was a carpenter with over 20 years. It was an attempt to get our local building inspectors to allow local wood to be used without going to the expense of bringing in a certified grader. I helped bring in a trainer to give them a one day quick session, didn't work, over 20 inspectors got up and walked out of the meeting. When I've talked to carpenters and sawyers alike everyone thinks they can grade but it is a little more complicated than most assume. I've worked in places where they don't care and have used lots of sawmill lumber, I have a small mill. Just cause a guy has a mill and is whacking up trees doesn't mean he's making lumber. I guess that's where I'm coming from.

A couple of ways to avoid worrying about it... no knots larger than 2" anywhere, no other defects. Or specify clear, or check with a larger mill if there is one nearby and see if you can hire a grader or I can give you contact info and they can send a grader to you. I could also give you a tutorial but it probably isn't going to cover everything. I can probably keep you out of real deep water.

Woodmizer and Timberking keep lists of sawyers if you do want to go that route there are also "find a sawyer" links on the Forestry Forum and Woodweb.

Yup you could use the ledger as part of the header, helps support the ledger too