OSB Vs Plywood for soffits

[Raider Bill]

What are your feelings on this subject?
Money is getting tight on this build. I am very close to being completed enough to move in although it will be primitive living for awhile.
Jimbo who is building his cabin on a shoe string budget brought this up last night.
If sealed on the edges and a good paint used why can't osb be used for soffits?
I've left osb and plywood out for a couple months and the osb seemed to weather it better. It did get discolored some but the plywood warped bad and started to delaminate.

[Rocky_J]

OSB takes a LOT more paint to seal it. And then it still looks like OSB. Why not just use a thinner sanded plywood? The soffit isn't structural so you don't need 1/2" and the thinner, sanded plywood will be less expensive than OSB. And cheaper to paint. And it will look better.

[beenthere]

.........If sealed on the edges and a good paint used why can't osb be used for soffits?
.............

There are many more "edges" to seal with OSB, than with plywood (like Rocky says )

I'd go with the plywood.  The 2 month outdoor test you made isn't a good test...IMO. Neither was good for the wood nor was it a realistic test for soffits (protection from rain and sun, and a good paint system is important). 

[Raider Bill]

It really wasn't a on purpose test It just happened that way.

What thickness plywood would you suggest 1/4"?

[Warbird]

Why not use sheet rock?

[Raider Bill]

Just checked the blue store. 3/8 ply not sanded is $11.23 4x8 sheet.

[Raider Bill]

Sheet rock? Don't see how that would work? Green board, blue board?

I did look at a log cabin where they used osb then covered it with poplar bark. Guy said critters didn't like the bark.
I have millions of poplar trees and the bark seems easy to remove but..............?
I don't know.

[Warbird]

Guess it depends on how you are building and where.  Inside my house, I framed out a soffit and then used sheetrock.  Of course, I didn't do a flawless job and the lines are not perfectly straight.

[beenthere]

It really wasn't a on purpose test It just happened that way. (I understand  )

What thickness plywood would you suggest 1/4"?

3/8" sanded is what I use. Seems to be a product designed for soffits, and will stay flat if 16" centers for fastening.

[Raider Bill]

My centers are 24"

[TexasTimbers]

OSB resists moisture much better, that's just a fact, but as mentioned you have the OSB look which is an unattractive finished look to many people.  It does take more paint, but not as much as some think unless you expose the wrong side of course. One side is much more porous.

I suppose you have ruled out Hardi plank for price concerns. Have you considered 1/4" or 7/16" hardboard? Hardboard has many advantages. I haven't priced it in a while but it used to be cheap. Also consider vinyl soffits. You can buy cheap no frills non-perforated vinyl soffit material and install your own cheap vents.

Don't forget soffit baffles! Proper ventilation is crucial. If not properly ventilated, your attic space will trap moisture. Excessive moisitrue will kill the effectiveness of your insulations ability to retard thermal transfer efficiently. You probably know this, but you would be suprised how many homes are 20 to 40% less efficient simply because of improper attic ventilation. Also do not mix types of ventilation systems. Don't mix ridge vents (my preference)  with anything else i.e. gable, power, turbine. They all fight each other. As a general rule you should not mix any two ventilation systems if they are functiong properly. Some say it's okay to mix gables vents with turbines but I do not like it either and don't want to explain why it's long.

General rule you need one square foot for every 300 sq. ft of attic space.

If you want to get real creative, you can scrounge real cheap underpinning and soffit if you have time to look or wait. Those piberglass pool skirts that often get trhwon away make great underpinning. That's what I used on or add-on. One side was slick as a babys hnd and it was 1/4" thicj. It will never rot or rust. It would work for soffit as well. The other side which has the fiber exposed is nearly slick but would hold paint much better. We didn't have to as we have a wrap-around porch around the entire house but you can scrounge many free and cheap soffit material types given time to scrounge.

[DouginUtah]

Why not use soffit vinyl?

I did.

\______/\_ __ __ _/\______/
                  Vent

[Raider Bill]

They are invented. The plan is to foam spray insulation on top of my ceiling dry wall and the gap between the roof decking and top of the ICF block thus sealing the living space completely. Space above the ceiling to roof deck will be dead air with no venting. If needed later I could put some kind of vent up there such as gable or solar fan.

Living area will be like a igloo cooler or refrig and all I will have to condition.

There are no ducts in this space. Peak is around 9' from top of great room ceiling to bottom of roof.

There will be no insulation under the roof decking.

http://www.buildingscience.com/documents/primers/bsp-042-read-this-before-you-ventilate-1

In my Florida house  I used Styrofoam soffit baffles from bottom vented soffits to vented ridge vent top and insulation.  I used them on every run all the way. [Bought a garage full of them cheap years ago]. Different climate. I also have thermoregulated gable vents but in my case they do not work against each other.
All ceilings here in Fl are also insulated to about r-30 or so. My florida attic is pretty cool even in the hot summers we have here.

Vinyl for me in Tenn might not be a bad idea. Won't work for Jimbo's cabin due to looks but I certainly can rethink my color ideas. White is right they say

The pool skirting idea intrigues me too.

HArdi board is too pricey for this IMO. Yes it's probley the best bet but as I draw near the end the $$$ is getting tight. I don't want to skimp in areas that need the most attention.

I am using hardi plank for my gables hopefully next trip.................  I keep saying that.

[breederman]

For the cabin he could use t&g pine. I am not sure how that would look on your house. I just put CWF on mine every so often to keep the color, but on your house that could be a real job?

[Raider Bill]

Yepper my end gables are going to be a real pain to cover and or maintain.
I am not looking forward to doing them.
The side soffits I can walk along the deck and touch them.

I'm still not sure what color the gable end are going to be put for sure I will paint the hardi plank on the grtound.

[Warbird]

Ah.  You mean something much different than what I meant by "soffit".  Sorry.

[ely]

i like breedermans idea best. i am actually going to use pine on my building, remember the outhouse? i will most likely use a rabbited edge instead of a true tounge and groove. thats if i can not cut a wide enough board to cover it in one fell swoop.
all i like is across the back of the building and both ends of it.

i guess i better dig that thread up when i get my pictures and update it, i know how we like pictures and all.

[ely]

Ah.  You mean something much different than what I meant by "soffit".  Sorry.

that is funny stuff warbird, when i read your initial post i was tryin not to spit tea out. then i guessed you were thinking different than he was or i was anyway.

then after i thought a bit i thought well maybe he was being fasicious, like yeah use sheetrock at least there won't be much hanging up there in your way when you get ready to do it right. :D

[breederman]

If you start the t&g from the out side and then from the house side
you can end up with the grooves facing each other and if you manage to figger right you can start at one end and slide continuous vent the whole length of the house. Raider won't need it as he has no ridge vent.

   

[Don P]

I start at the fascia with the groove out, rip the tongue off, put in a strip vent, then another detongued then whatever it takes to finish. On a wider soffit there can be several boards each side of the vent, I face nail with a trim nailer.

We did one log house with bronzed aluminum soffit and aluminum fascia, it actually didn't look bad. I do prefer wood though. I hate ply or osb on soffits but thats just me, got 3/8 ply on mine  :.

[WH_Conley]

Bill, only thing that would bother me would be the " dead air, no venting". Got to vent the attic space or deal with water. Vented ridge cap and a few vents on the eves will take care of this. Maybe I read your post wrong, but, you got to have air flow. I like the idea of sealing off the living space.

[Raider Bill]

I was going to put good sized gable vents up to vent until I started reading new building technoligy sites. They say if the attic isn't vented and the liveing space well insulated there won't be any condensation, no air movement no problem :-\
The front gable south west towards a valley and generally gets a nice breeze through.
I've got a few weeks to think this over so I'm open.

Sometimes I think to much into things.

Even if I put up durarock I'll still have to repaint it from time to time so maybe vinyl siding for the gable ends would be best along with vinyl soffits. Done and over with. They got tans, greys etc. If I remember right it runs about $60 a square plus channel and trim.

By the time I'm done I won't have any wood on the place :'(

[Radar67]

I would put the gable and soffit vents in. If there is a variation between inside the attic temp and outside temp (especially if the sun hits the roof) there is a possibility of condensation. No air flow equals rot. Just my dime's worth. (inflation ya know)  ;)

[Handy Andy]

  Where did you get this info that you don't need attic vents if your attic is insulated?  If not ventilated moisture will collect in your insulation.  Then the insulation doesn't do it's job.  Sounds like wishful thinking. When I built my house, limited funds, I used 1/4" plywood for soffit.  Put my nailers on 2' centers, then when I upgraded it, had the plywood to screw the vinyl soffit to. Worked pretty well. 

[Raider Bill]

http://www.buildingscience.com/documents/primers/bsp-042-read-this-before-you-ventilate-1

This is one of them.

It doesn't make sense to me either but seems to be the new way of thinking :P

I believe the thinking is if you don't insulate the roof deck and super insulate the ceiling the temp will be close enough that there won't be condensation. Plus with no air flow nothing in nothing out.
It's confusing.

Prior to this I would have always put in vents. Probaley still will.