Finally siding my house (T-111 with grooves on 4″centers onto OSB). This is 8′ material and I’d planned to use Z flashing for the horizontal seam at the gables.
But now I’m thinking instead to fir out the gable so that the gable panels hang over the wall panels a bit: *(attached drawing)
There are three gables, 24′ – 26′ wide 4-12 pitch.
How thick would you make the firring strips? Should the one on the seam be treated?
Replies
You furr out the same thickness as the T-111. Your rake trim needs to be able to accommodate the extra thickness. Could not get anything off your attachment so I don't know the specifics for your situation.
So I could rip strips off T-111 off-cuts? The worry there is that without a space between the back of the top sheet and the face of the bottom sheet, I could get water up in there to start all sorts of nuisance. I'm thinking more like 1" - 1 1/4" fir-out.
The eave overhangs ~ 12" so no problem there.
I don't know why water would get in, but if you are worried, couldnt you use flashing between the top 8' of panels and the bottom, so water getting in exits at the horizontal seam? If I were bothering with furring, I would use 2x2's vertically under each edge where one four foot panel butts the other, put felt or flashing on the furring before the panels and use flashing where the top panels butt the lower panels horizontally and put screen in the open (lower ends of the upper panels) to keep bugs out and that way any water would go right out. But, really, if you use house wrap or even felt (tarpaper) over the sheathing, that should direct water down to the z-flashing between the top and bottom panels and out.
I'm just guessing about your job. T-111 is more often used on sheds and garages for me. In those cases we use the T-111 as siding with no sheathing. Generally the gables are covered before they are stood. The T-111 is figured to overlap the pieces on the wall. I don't use Z flashing on an overlap but you certainly can. In your case, a retrofit, there isn't any reason to overlap unless you think the shadow will look better. I'm not sure where you think that water entrance will be a problem. I suppose it would not hurt to run some felt or Vycor under the vertical joints in addition to caulking them. You can cover the top edge where it meets your overhang with a molding . Here is a quick sketch in elevation. I left out floor or ceiling joists but I think you can get the idea. I like to land on something solid with the edges if I can. T-111 rips can be used as well as anything else that is close to the thickness. I surely would not furr it out far enough to leave an opening unless you want to help out the bat and bug population. Hope I'm understanding your question.
Thanks for your consideration and detailed drawing. That looks like the best solution, although I'm tempted to just butt the bottom of the top sheet right on the Z flashing, with about a 1/2 " space. That's the way I've done it before, but have noticed some de-lamination of the plys along that edge (after 8 years)where I wasn't careful to leave a space. I think the T-111 edge sat in water that stayed on the flashing during heavy, long, or wind-blown rain long enough to soak some up.
I'll run your detail by DW and maybe try a sample to see how the shadow looks.
It would be a good idea to at least seal the top and bottom before installation. We often prime and apply one top coat before installation on many materials. Much easier to do on the bench. I would not hold the gap too much but you may have an idea there. A small gap would also give you a little fudge factor if you have to stack a few and keep the grooves plumb and inline. Nickels get used for gaps around here all the time, they are just about 3/32". When it comes to putting that stuff up on an existing building, the easier the better. Here is a link for some info on Texture 1-11 plywood siding from Georgia Pacific. There are different grades. For the higher quality jobs we prefer the clear sheets in fir. There is a significant cost difference between that and the southern pine with the footballs.
http://www.gp.com/build/PageViewer.aspx?repository=bp&elementid=3860
This has all actually been pre-finished with two coats of Cabot stain, including the edges, and the backs are primed with linseed/turp. As we put it up we are re-coating all cut edges around windows, trims, etc, with the Cabot.
Amazingly, although this is SYP, there are NO footballs and only a very few fills, which we are mostly getting into the off-cuts.
Sounds like you've got all the bases covered. Have a safe and pleasant installation.