Author Topic: 20' floor joists?  (Read 2526 times)

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Offline jbar

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20' floor joists?
« on: November 29, 2006, 04:38:40 PM »
Ok, I bought the 20x30 1-1/2 story plans...have to take them to an engineer, $1800, to have them redrawn for 110mph winds, etc. I live in Florida. Anyways, I've been looking at standard size 2x12's and the longest "standard" size I found was 16'...are you guys special ordering your 20' floor joists? I was hoping everything in the plan was standard size so I wouldn't have the additional costs of special ordering. Any suggestions?

Thanks.

Offline John_M

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Re: 20' floor joists?
« Reply #1 on: November 29, 2006, 05:36:17 PM »
If you are talking about the joists for the first floor, you could use an engineered I-joist.  They can span very large distances.  If you are talking about joists for the second floor, you would have to use built up beams or perhaps fit in a load-bearing wall on the first floor.

I'm sure John's plans explain all of your 2nd floor options!!
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Offline jbar

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Re: 20' floor joists?
« Reply #2 on: November 29, 2006, 06:28:46 PM »
I thought the whole idea of the plans were to not have load bearing walls on the inside of the cabin. Looks like I'll have to special order the 20'ers...or shorten the width to 16'. Bummer.

Offline glenn kangiser

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Re: 20' floor joists?
« Reply #3 on: November 29, 2006, 06:32:05 PM »
I used to get 20' 2x12's at the lumber yard, no problem.  I know I made a carport without special ordering anything, however it may depend on your yard or location. :-/
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Offline bartholomew

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Re: 20' floor joists?
« Reply #4 on: November 29, 2006, 06:48:43 PM »
You might have to look around for 20-footers. The local big box stores here don't seem to carry them but at least one of the smaller contractor-oriented lumber yards has them.

Offline PEG688

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Re: 20' floor joists?
« Reply #5 on: November 29, 2006, 07:03:50 PM »
The big box boys would have to spec order, I think, not sure they could even do that , might be outside of their big box system :-/ :-/   My local yard only carries a few 20' ers , for a job like yours I'd go to a good yard and order them . It shouldn't  a true "special " order but 20 ft-ers don't just fall off the truck , well they could but ya know a lil joke .

[highlight]  They would be uncommon / not sold every day / rarely called for item, so ordering them would be best [/highlight]. The supplier seem to do a better job storing lumber , or they move so much of it that the lumber doesn't lay out in the weather, suns the worst thing on lumber around here. More stock is lost in summer due to quick irregular drying than in the other season we generally have which is called spriall (spring / fall) although for the past week we have been transported to Nome, Alaska  ::)

  So back to your lumber shouldn't  be any more costly , other than it will be more total brd. footage , than your standard 2 x12 stock.    And you'll end up with better looking / straighter stock MTL  ;) YMMV depending on the current supply they have on hand .

  G/L PEG
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Offline John Raabe

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Re: 20' floor joists?
« Reply #6 on: November 29, 2006, 07:04:13 PM »
See the foundation sheet page 1 - you can use engineered joists if you want. I show two different brand specifications. They are available from just about any supplier.

It is getting harder to get the best quality 2x12's - and you don't want crummy ones for that span - too much bounce.
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Offline PEG688

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Re: 20' floor joists?
« Reply #7 on: November 29, 2006, 07:07:29 PM »
To add to John's post , I wouldn't max span the I joist either , I have found they bounce as well when max spanned, a taller (height wise) I joist than called for will reduce that tendency.

   Edited to add in the crawl space you could reduce that span issue by adding another beam , not so easy for your 2nd floor ceiling /foor joist.
« Last Edit: November 29, 2006, 07:09:54 PM by peg_688 »
When in doubt , build it stout with something you know about .

Offline John Raabe

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Re: 20' floor joists?
« Reply #8 on: November 29, 2006, 07:27:54 PM »
When I design for I-joists I design to their high performance 1/480 deflection span. Code min is 1/360 and I agree with PEG. that can be a bit bouncy on a long span like this.

We've had lots of folks use 20' I-joists on this plan without problems.

PS - I've heard of others in FL getting hit by high engineering fees. I'm sure they have new requirements and since all plans must have the review you don't have much choice.

My guy up here does similar work for local plans and charges $300. (He doesn't redraw the plans just adds notes and details.)
« Last Edit: November 29, 2006, 07:35:22 PM by jraabe »
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Offline jbar

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Re: 20' floor joists?
« Reply #9 on: November 30, 2006, 04:36:19 PM »
Thanks for the responses.  :)

I'll have more about building in Florida later...

Offline tc-vt

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Re: 20' floor joists?
« Reply #10 on: November 30, 2006, 06:37:01 PM »
I used Boise AllJoist AJS-20 I-joists in my 20x30.  They are roughly 11 7/8 inches wide with 2x3  edges.  The web is 3/8 inch OSB.  The I-joists are full span only in the middle 10 feet of the 30 foot length of the house.  (There is a partition wall at one end of the house and the stairs at the other end).  They are spanning a few inches less than max. spec for a L/480 deflection.  There is some noticeable bounce but all I have so far are the joists and the glued and nailed subfloor.  Cross bridging, strapping and the ceiling I expect will add some rigidity but going up one size on the I-joist will add rigidity at small additional expense.  They are also available with 2x4 edges for a stiffer design.

Tom

Offline tibadoe

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Re: 20' floor joists?
« Reply #11 on: December 01, 2006, 12:34:51 PM »
I would go with the I joist for a 20' span.  In VA I can order 20' 2x12's from our local mill but the quality of the cut trees is going down hill.  Just my 2 cents.
Joe