Replies

1. 
   Gerard_D._Yankowski | Jan 02, 1999 07:54am | #1

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   The merits btween OSB and Celotex...OSB is a wood product adding tortional rigidity to the structure with little if any insulating value. Where celotex has little if any tortional stregnth to it but a little more insulating value. Osb is cheaper than plywood and celotex is very cheap per sheet that is why you see cheap builders mix and match both.
   Recomondation.....sheath your home in 1/2" or 5/8" plywood NOT Osb or Celotex and insulate your walls according to the recomended R values and then some for the area you live.

2. 
   Patrick_M. | Jan 02, 1999 08:10am | #2

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   Cole, Gerrard

   Seems like an apple & oranges question to me. Celotex (polyisocyanurate foam enclosed between reflective foil facers) has the highest R value per inch (7.4) of any avaliable insulating product, and a price tag to match. It is extremely excellent insulation and with the seams taped with their special foil tape forms an effective air barrier . . . sheathing board it ain't nor does it pretend to be, but I wouldn't put the boots to any one that uses it instead of OSB or Ply. Hopefully those applications use some other form of diagonal bracing which are approved by their Code. I personaly always use 1/2" ply but the cheapsters around here use 1/4" Chipboard/Aspenite and I doubt any of them have even heard of Celotex/Thermax.

   Reflectively,

   Patrick

1. 
   Gerard_D._Yankowski | Jan 02, 1999 08:26am | #3

   *PatrickThere we go building JUST TO CODE seems to be prevelant in todays quick and cheap enviroment.Sincerely, Gerard

3. 
   Guest_ | Jan 02, 1999 08:44am | #4

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   Patrick, I think Cole is referring to a different Celotex product than you are. I have a hunch he means the 1/2" fiber-like sheeting that resembles the material they use for asphalt expansion joints. This stuff was used on zillions of factory built houses for the last 30 years and is still available.

   I also think there is some confusion about "OSB". OSB (Oriented Strand Board) is a product meant to be used as an alternative to plywood in spanning floor joists,roof trusses ,etc. The product most commonly used for wall sheathing is actually waferboard (Blandex) , which is just a composite board made of large chips. I see these terms interchanged all the time, but they are two distinctly different products and should be used accordingly.

4. 
   Don_ | Jan 02, 1999 08:47am | #5

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   Gerald,

   Since money seems to be no object to you, why not use maybe 3/4 t&g kiln dried hemlock?

5. 
   Guest_ | Jan 02, 1999 09:41am | #6

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   Yea but, using osb at the corners for strength is perfectly acceptable. Sure we could all use 3/4" plywood to sheath walls but that is impractical and a waste of wood. I'm not saying Gerard is wrong, in fact he is correct as to what I know Celotex to be, but to blast anyone for using only osb at the corners is wrong. I have done it both ways, and my preferance is to sheath in at least osb, but celotex or R-MAX as I know another description offered is not bad. I have seen numerous details showing all foamboard with let in braces (wood or steel) in FHB.
   We seem to be dealing in an option based industry and if all plywood sheathing knocks out the worldpool / soaker tub, they will opt for the other guy. Maybe we just need to br better salesman, but this will be a tough sale. I will state I do not advocate slackass stanards to get work, but the original thread was not about sub-standard work. Many architects spec this type of system. Of course they are architects.

6. 
   Greg_Booth | Jan 02, 1999 09:49am | #7

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   Hey Patrick, I thought celotex was a really flimsy and cheap pressed fiber board with limited R value. It's a totally different product than Thermax, which is like you describe. Apparently celotex is approved as a structural sheathing some places but I'm not sure why.

1. 
   Mike_Merisko | Jan 02, 1999 11:29am | #8

   *I do not see the use of Celotex foam sheathing as being synonomous with cheap builders, but as a way to maximize the R-value of a newly constructed home. Plywood, OSB, or let-in bracing is needed with this product.

1. 
   Gerard_D._Yankowski | Jan 02, 1999 07:30pm | #9

   *DonDon name is Gerard not Gerald. No not advocating unlimtited funds be present when it comes to home building (Wish they were) but I thought this site was "FINE HOMEBUILDING", just to code ...yea that is fine for "BUILDER" let them have it.

1. 
   Patrick_M. | Jan 02, 1999 09:19pm | #10

   *GregI've got a 4x9x1" sheet of Celotex standing in my shop. It is as I described, polyisocyanurate foam enclosed with foil facers. In HUGE black diagonal lettering all over one side of the sheet read the words CELOTEX and in slightly smaller bold lettering THERMAX. It is made by the Celotex Corp. of Tampa Florida. I suspect what you guys are talking about is Exterior Tentest known in Ontario as 'Black Joe', basically pressed sawdust with a tar type facer, and it certainly qualifies as cheap s*it, and in 20 odd years I have yet to hear it referred to as Celotex. Celotex/thermax is a code approved insulating material around here, not a structural sheathing material. Regional differences. . . Or maybe local common terminology/slang getting to much usage?Happy New Year anyway!Patrick

1. 
   Patrick_M. | Jan 02, 1999 09:42pm | #11

   *GerrardCool your jets sport, if you read my post I quite clearly state that I always sheath with 1/2 ply, this is a non negotiable detail with me. I was merely assuming that we were talking about the same product: polyisocyanurate foam board,(read my other post below) not pressed sawdust and tar, and deducing that the use of such an expensive exterior insulating board meant a concientious builder, who like myself builds in excess of the code, and would have used some code approved, and legitimatley structural, diagonal bracing. Now if we are talking about a structure with vertical ply, or chipboard at the corners with the rest of the walls sheathed with this sawdust board you guys, I think mistakenly, call celotex then I agree that it is crap construction and I wish I could say that it doesn't happen around here but it does,a lot,but not on my jobs!It's 25 below here, and I've gott go shovel snow. . . later eh?Patrick

2. 
   Bob | Jan 02, 1999 09:44pm | #12

   *"Celotex" as most know it is what is know as an AIFB (asphalt inpregnated fiberboard). It's use has been traditionally as a non strurctural sheathing applied to stick framing. Being a non structural product the framing must be strengthined at the corners for shear by diagonal bracing etc., this product has little R-value but is somewhat effective in breaking the thermal bridge between the outside and the wall studs. Celotex the company also makes a poly iso sheathing board that is also non structural and is used for the same purpose as the AIFB. However Poly Isocyanurate foam is highly unstable due to its structure. The trapped gas that is giving this product its high initial R-value of 7 per inch is constantly offgassing and the products efficiency decreases and eventually will become totally ineffective. Not a good choice and this type of product is being phased out by regulations against CFC's anyway. Or at least should be----OSB (Oriented Strand Board) is a structural rated sheathing by the APA (Amercian Plywood Association) and the 7/16" product is fine for use as such but has little or no insulation value. This product has been around for awhile now and has been very beneficial in the manufacturing of Structural and Semi-Structural Insulated Panels due to its ability to be manufactured in longer lengths and wider widths than plywood. The composition of OSB is such that the resins binding the strands is now polymer based and the product will withstand moisture much better than the earlier urea-formaldahyde resins. Still need to seal against moisture but no different than plywood. Engineered wood products such as OSB and TJI's are fast becoming the materials of choice for today's building industry. There is no need to be scared of these products and the resistance to change that is inherent to our industry is the only stumbling block I see these products up against. They are well thought out and have the ability to use sustainable yield resources that will ensure the building trades to endure the new millenium.

7. 
   Guest_ | Jan 03, 1999 04:56am | #13

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   Eh, Bob? Totally ineffective? R = 0? I thought it degrade to about 5.5 or thereabouts over a ten year period.

1. 
   Guest_ | Jan 03, 1999 06:53am | #14

   *Just a thought guys. Ever looked a house that a hurricane or high winds have damaged? Look at what stood up and what fell down. Then ask your self why? Then ask what could I have done to prevent this?

1. 
   Guest_ | Jan 03, 1999 06:58am | #15

   *While I'm sympathetic to your cause, what about places that never have huricanes?

1. 
   Guest_ | Jan 03, 1999 07:30am | #16

   *Do you then have to extend all the jambs?

8. 
   DRapps | Jan 03, 1999 08:28am | #17

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   Just a note on some of the information on this thread. Celotex manufactuers all the product mentioned above fiberboard sheathings and polyiso sheating Thermax and Tuff R. The poly iso board are R 7.2 per inch stabilized R value. I believe NAHB web site has info on the testing.

1. 
   JohnE | Jan 03, 1999 09:37am | #18

   *Bob;The resistance to change especially in the area of Engineered wood products is a warranted by builders.Remember, the b APAis the same organization that span rated MDF for subflooring.Cheers;JE

9. 
   Guest_ | Jan 04, 1999 07:41am | #19

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   Hi Bill

   Thanks for the support.Like Joe I've got a few years in this too and I'm always tring to improve on what we do.If a building is damaged I want to know why and if we do this can we prevent it? I don't want a client to see me in a few years and say that their house, that I build is a piece of junk.We started a owners manual for the work we do for home owners and EVERONE WHO WORKS ON THE SITE IS IN IT. Most subs will go out of there way to do a better job if they know that they are going to be in a book that tells what they did.Getting back to the hurracanes, well just about any high wind gusts can damage a home. Sorry if I sound like a broken record but we build to fix problems before they happen.Saves on comebacks and I always have a good rep with my clients. We are seeing a lot of work that is coming from clients that we have donne work for,so do us thhis apporach is working.

1. 
   Guest_ | Jan 04, 1999 06:22pm | #20

   *The AIFB referred to earlier is called "Homasote" around here (Rochester, NY) and is not a very good sheathing or insulating material. It does insulate better than ply or OSB, but it's usually used to deaden sound, or for expansion joints. I also do not see why this stuff is put on the outside of the house in the North east. This is a pressure barrier and a vapor barrier. When this is placed on the outside of the wall, doesn't it allow air access to all the different leakage paths through the wall? Won't this also stop moisture transmission and saturate the wall because it can't escape now? I thought CW (conventional wisdom) said foil faced ISO board (celotex around here) went on the inside.-Rob

10. 
    Gerard_D._Yankowski | Jan 05, 1999 09:23am | #21

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    Joe
    Like the way you think with regards to quality!

1. 
   DAVE_WILLIAMS | Jan 07, 1999 08:40am | #23

   *GO WITH OSB THEN USE TYVEK TO COVER YOUR HOUSE ON THE OUTSIDE. THAT WAY YOU GET STRENGTH AND A VAPOR BARRIER

11. 
    Guest_ | Jan 07, 1999 08:40am | #22

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    What are the merits of OSB vs. Celotex
    and other sheathings in terms of cost and insulating value? Builders in
    our area (ND) are about split in application.