lkazanov2
Basic Member
Posts:177
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| 12 Jan 2009 06:01 PM |
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Guys,
Need some opinions of pro/con of attaching the floor system. I am planning 1.75" LVL J bolted to the ICF, 16" OC (spaced to avoid the joists). I am planning on open web floor trusses. I am looking at OJ 2000. It has been suggested to me to use floor trusses and mounting to the LVL using their top chord, then small filler for the height difference in between the joists for the subfloor. Using this method (which I like) would eliminate the costs of the joists hangers. Opinions?
Thanks,
Leonard
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BrianW
New Member
Posts:6
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| 12 Jan 2009 06:25 PM |
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Open Joist 2000 are trimmable trusses and are only meant to be bottom bearing.This means you would need to use them with hangers. Top bearing trusses need to be ordered as such. Keep in mind the price of the LVLs which are pricey. You might want to consider the hangers that are inset to the forms before pouring that do not require a ledger.
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lkazanov2
Basic Member
Posts:177
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| 12 Jan 2009 06:51 PM |
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Brian,
Thanks for the reply...correct, the OJ 2000 cannot be chord mounted. I know that ICF Connect hangers are likely $5-6.00 per set and would not require an LVL (still have to fill in for the subfloor between the trusses). That is an option. I am trying to find the least expensive, most squeak free way to attach the floor system. |
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Buntly
Basic Member
Posts:162
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| 12 Jan 2009 07:17 PM |
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In the past I have used a double 2x8 ledger. Screw 2 2x8's together just to hold them tight. Drill holes thru the double 2x8 ledger and attach ab's. Install ledger prior to pour. This will keeps wall straight during pour and gives you a 3" brg surface for joists. Much cheaper and lighter than a lvl ledger.
Bunt |
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lkazanov2
Basic Member
Posts:177
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| 12 Jan 2009 07:19 PM |
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Bunt,
Thanks again as always...I am seriously studying your recommendations. |
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Alton
Veteran Member
Posts:2157
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| 12 Jan 2009 07:30 PM |
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Bunt,
Should the two 2x8's be put together so that the crowns are opposite - one up and one down. On regular made up beams where I glue and screw 2x's together I always alternate the crowns to make the beam level. This avoids making a camber in the beam. Should this also apply to ledgers? |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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Buntly
Basic Member
Posts:162
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| 12 Jan 2009 07:54 PM |
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I find the straightest 2x8's I can and screw them together in the best way such that the tops line up. I've seen 2x8's that vary from 7 1/8 up to 7 5/8". The most important thing is that the tops line up to provide a 3" brg surface for the joist. Strength of the 2x8's is not an issue really since the ab's are typically 12" or 16" o.c. There will be minimal bending and/or deflection of the 2x8 ledger over a 12" or 16" distance. One thing to consider, depending on the span of the joists is that an appropriate species of 2x8 (or whatever size ledger is being used) is used. Here in Michigan, spruce is common. The perp to grain properties are much less than southern yellow pine. Most of the time spruce works, but there are times when syp is needed because of the end reactions of the joists and/or trusses. I guess if one really wanted to, they counld cough up some $$ and use a 3 1/2" wide deep lvl. This would eliminate the connection issue of the 2 2x8 ledgers. Last I checked, I think a 9 1/4" deep x 3 1/2" wide lvl was arount $9/foot.
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lkazanov2
Basic Member
Posts:177
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| 12 Jan 2009 08:46 PM |
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Bunt,
So ideally southern yellow pine would be best? I know this is the strongest of the "framing" lumber but I thought that it is usually wet and not dimensionally stable? I know that much PTL out there is SYP. Am I correct on this? |
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Buntly
Basic Member
Posts:162
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| 12 Jan 2009 09:12 PM |
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Syp is typically the most sensitive to moisture form what I've seen. It is one of the more dense framing lumbers. In service though, if a proper environment is maintained,...there are no issues. Much of the lumber trusses are designed with are syp. The nail and screw holding values are significantly higher than typical spf. Many framers I know do not like trusses with syp chords. It's more difficult to drive nails in, etc. Many girder trusses are made with syp becuause of the properties of the syp. (higher hanger values and larger bearing capacity). If you have a copy of NDS, you can compare the properties of syp to spf,.......you'd be surprised at the difference. Most of the time though spf or similar is sufficient.
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James Eggert
Basic Member
Posts:411
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| 12 Jan 2009 10:32 PM |
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ik
It is doubtful that 1/2 ABs at 16" oc bolts is providing the proper bearing for floor loads, however, you don't say whether or not you are using 2 ABs per 16"? I have used 3/4" before as singles. By the way, I like the OJ2000 stuff, and am incorporating it into a project again!
Bunt
I'm not following why you would want the 3" bearing showing under the joists? I guess in the basement it wouldn't be more than a visual thing, but what about in a 2 story house? I don't see this as a 3" ledger that you are using joist hangars with? Or did I not understand your method?
However, each of these AB placements would typically have the foam removed behind the ledger so the concrete flows against the back of the ledger! |
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| Take Care<br>Jim<br><br>Design/Build/Consulting<br>"Not So Big" Design Proponent |
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lkazanov2
Basic Member
Posts:177
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| 12 Jan 2009 11:37 PM |
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Jim,
Thanks for replying...yes, I am calling for two 1/2 or 5/8 AB's at 16" OC for the ledger. Foam will be cropped 6" around the AB. I believe PCA 2007 allows 4" cropping for 1.5" for EPS foam and then 1" additional for each 1/2" increase in thickness of EPS. I will have my engineer verify. Bunt is referring to use the top chord of the truss to hang on the ledge. The width of the ledger will be "absorbed" into the depth of the truss. The wider the ledger the larger the bearing surface for the top chord of the truss. I would imagine that a 16" truss could easily accommodate a 2x8 or even 2x10. |
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OnTheLevel
New Member
Posts:15
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| 13 Jan 2009 03:37 AM |
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What about using a brick ledge to support the bottom chord? Absent that, what about using 8 inch block to build a ledge, then using 6 inch there on up to the truss plate? |
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Buntly
Basic Member
Posts:162
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| 13 Jan 2009 07:05 AM |
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Jim, the 3" brg is not required as you mention. However, 1 1/2" is min brg width by code. If I am bearing the joists on top of the ledger, I sometimes find it difficult when I have only 1 1/2" to bear on. If hangers are used with a single 2x member, there is a significant reduction in the hanger capacity. (typically about a 36% reduction depending on the hanger, per simpson catalog).
Most of the time, a single ledger is fine as you mention, but many times I use 14" deep floor truss or joist to span larger distances and/or spacings. These joists have a larger reaction than a typical floor joist and many times the hangers will not work in a single 2x member.
PS, Jim I just re-read your question,.......... and I typically use a top chord bearing floor truss when I use a dbl ledger, so the ledger is hidden. If I use hangers, I typically use a ledger the same depth as the joist and use face mount hangers. I always hide the ledger as you mention. There's no reason to have the ledger exposed either in basement or above grade
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thagreen
Basic Member
Posts:283
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| 13 Jan 2009 11:51 AM |
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onthelevel,
You're wright, I hhave done the 8'' to 6''. Personnaly I don't think the extra money for the cement, etc. is worth it. To do this you have to pour at least 1 block of the 6'' w/the 8 which demands more labor and harder to align but very doable. The ledger w/ hangers is quick and easy.
For you guy's whom put on the ledger before the pour how do you deal w/ the compression factor of the block ?A 2x down to footing? Makes for alot more wood (cemented)does it not? |
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Buntly
Basic Member
Posts:162
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| 13 Jan 2009 12:33 PM |
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When and if i install the ledger prior to the pour, i typically transition from a 11 1/4" icf to a 9 1/4" icf. I do the top of the pour with 9 1/4 then i rest the ledger on top of the 2" transition and screw the ledger to the 9 1/4" block, and the bracing to the ledger. If I am using the same wall thickness all the way up, I will rest the ledger on top of the bracing with shims or stud down to footing. I will only do this with a block I am confident with (one with minimal compression). There are a few blocks I have used that I wouldn't attempt to install ledger prior to pour.
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OnTheLevel
New Member
Posts:15
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| 13 Jan 2009 12:58 PM |
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I was told a local contractor did the 8 inch and 6 inch for a commercial job. I was wondering why you couldn't/wouldn't use a tapered/brick ledge to hold the rim joist and truss? |
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Buntly
Basic Member
Posts:162
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| 13 Jan 2009 01:08 PM |
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In most cases a 6" concrete wall works below grade, so if you want to create a ledge for the rim, the basement must be 8". Most people don't want to spend the extra $$ on concrete. I guess you could do a 6" below and a 4" above, but most contractors I know prefer not to pour a 4" wall. Using a brick ledge to create a floor ledge creates other issues such as getting wiring/plumbing up to next floor as well as a profile in the living area which needs to be dealt with.
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thagreen
Basic Member
Posts:283
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| 13 Jan 2009 01:16 PM |
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Most probably the commercial job was engeneered as such(structurally stronger). There is no reason why it couldn't be done other than $. The brick or tapper are mostly used on the inside to accomodate a hambro flooring system or other cement floors.
Cheers! |
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