OSB Vs. CDX

FRAMERBEN

Most of the time I think that old schoolers have the right approach but in this instance , I believe opposite. We work for a builder who swears by cdx over osb. I think that he needs to look to new horizons and bow down to the osb. If cdx gets any water on it, it immediately wants to buckel and go every which way. Yes, osb might swell after a little water but it stays much more true.

currently we are framing a new porch on an existing house. teh plans call for 1/2 ' plywood behind the 4x8x1/2 sheets of azec the we will be using. the builder ordered cdx. It got wet. We had to go back and litterallt nail the stufff 3" on center to take all the buckels out of it. point being, Listen to new innovations , in some instances. Any thoughts? ben

Ed the Roofer

Hi FramerBen,

The differences you point out do not begin to scratch the surface of the issues with OSB. If the job affords a premium product, I have been swayed to the disciples of a product called Advantech, but it would not be competitive for roof bidding purposes.

Please read through this pretty good discussion about the differences and then share some other thoughs to bring it back up again.

http://www.contractortalk.com/f15/plywood-vs-osb-18291/

Ed

A W Smith

That is true for southern yellow pine CDX which I refuse to use. But definatly not doug fir cdx.

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Ed the Roofer

AW,

Do you have any documentation to pass on regarding the differnce between DF and SWP?

An estimator once asked, when confronted with the question of which of those two were better, he replied with the following question:

What kind of leaves are on a Douglas Fir?

Ed

A W Smith

here ya go
http://www.centralforest.com/species.htm

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KentWhitten

That is exactly what I want to say. SYP blows, Fir does not. I wouldn't put that crap pine ply on a dog house. Advantec ply is good, we make it here in Maine. Most people use it for the subfloor, I've seen a few do it for wall sheathing. I hope it gets all of the suppliers switching. Good product.

I think there's good and bad. I've pulled off some siding that had a leak and the OSB was mush. I don't think CDX Fir would do the same, but I'm sure it'd be black or rotting, but not oatmeal. I think OSB is perfectly fine to use everyday as long as it doesn't get too wet. A rain or two doesn't hurt it.

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Kingfisher

I only use advantec subfloors. Do they make 1/2 & 5/8 for sheathing too

DrewD

yeah you can get 5/8 both straight edge and T&G, an not 100% on 1/2" though.

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adcoleman

Around here Advantech 5/8" T&G and 5/8" Doug Fir CDX are about the same price and IMHO Advantech is a much superior product. I use 3/4" or 7/8" Advantech for floors, 5/8" for roofs, and 1/2" for walls.

neolitic

There is a world of difference
in CDX.
I think most of the kids that hate it
have only worked for cheap skates
who order 3 ply, what ever is the
lowest price.

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Joe Carola

That's not true where I'm from. I'm using cdx fir and never have any problems with it getting wet.

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KennMacMoragh

All of the new construction around here is done in osb, except when the plans call for structural I plywood on walls. But remodels are different, occasionally our engineer specs out plywood. Sometimes the engineer doesn't care, sometimes he wants plywood, I don't get it.

As far as plywood being more durable when something goes wrong, I'd like to see proof of that. Lately I've been doing several fire and water damage restoration jobs. And plywood rots just like osb rots. If a building leaks, sheathing has to be replaced, doesn't matter what they used.

And if it gets wet during new construction. You can have problems with either one, the osb will swell and bulge at the seams if you don't gap them. And the plywood will buckle, I call it curling, it makes a bunch of waves. But that's pretty rare, you have to let it sit out in the rain and get dumped on for a while before covering it if you're going to have that problem.

So yeah, I still don't get it, why some engineers and I guess a few builders still insist on using plywood.

wallmaxx

Try 5 ply or 7 ply marine grade plywood....costs a butt load but it is AWESOME.

neolitic

There you go!
Marine would be a bit of over kill mostly,
but it sounds like a lot of folks forget
that you can get 5 ply rather than 3.
Fir when it's called for (not so easy back here),
YP when it will do.
You don't have to buy the cheapest
thing the Box wants to sell.

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Meetre

ply is just like drums, more layers=better product. why anyone one uses 3 ply where it could get wet is beyond me.

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dayspring

I agree, I'd much rather use osb than a 3-ply CDX, however, I do like and use 4 ply + plywood from time to time. Avantech is a very good product and I've been using it for subfloors and roof decks for a couple years with not one problem.

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Ed the Roofer

While nearly all of my competitors use OSB and 3-ply plywood, I point out in writing that I use either 4-ply cdx or 5-ply Douglas Fir. Along with making a bold point about what I do use, I also briefly touch on the reasons I will not use the other products which I consider to be inferior.

It may be the deal maker or the deal breaker, because my prices are higher, but the quality is more time tested.

Ed

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BirmanBuilders

An inspector once told me that OSB is stronger laterally, while CDX is stronger vertically. To me lateral stregnth is more important, studs carry the load down to the foundation not the plywood. I prefer OSB especially when dealing with nine or ten foot walls,just get 9 or 10 foot sheets. You can't get CDX in anything but 8X4 sheets around here, don't know if it's available anywhere else. The fir CDX is great for sheathing roofs, seen a few builders use the regular crap and will barely hold a mans weight. Still like OSB though, don't like the buckle in the cdx after moisture gets in it.

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neolitic

One can order plywood in
9' and 10' lengths.It's fairly common
in architectural grade HDO.

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dlcj

Advantech rules. We used it for the first time about 5 years ago on a new house subfloor (80 sheets 3/4" t&g). The h.o actually found out about it and special ordered it. It was not availabe here at that time. That house got about 20" of rain in 3 months on the floor before we could get the roof on it. The floor did not even show a sign of distortion so we've only used it sense. Right now 7/16" osb sheeting is 1/2 the price of 1/2" 4-ply cdx. Its alot easier to handle and get to lay flat too. If it gets wet on the walls it does swell a bit but it will stay flat. That house earlier mentioned the h.o also found out about and orderd 7/16" osb with a foil backing thermal barrier on one side for roof sheeting. It was only about $2 a sheet more at that time.