Installing T11 Siding where the joints meet

[mancave]

I'm building a cabin and plan to use that T11 siding. If you dont know what that is, it's plywood with vertical grooves to make it look like individual boards. In some ways, it's similar to paneling except for exterior use.

Anyhow, the sheets are 4x8 foot, just like regular plywood. The walls will be 8 ft. so on the side walls these sheets will cover right to the roof overhang. The problem is that on the end walls, where there is a gable, I will have a horizontal joint where the wall sheets meet the sheets on the gable. I really dont like the idea of just butting the sheets together, because water will get in, which will not only cause decay of the plywood ovfer time, but also get inside the walls.

I've considered applying a bead of silicone caulk to the joint before placing the sheets in place, but there is no guarantee that I'll get

100% of them sealed, not to mention that I intend to apply a paint or wood stain when the walls are complete, and I know well that paints do not adhere to silicone caulk.

However, I'm wondering if there is some sort of material made specifically for this use? I'm aware that when butting together some pole barn steel, they sell a special metal trim (divider) piece that sits under the upper sheet and has a lip over the lower sheet. I've already considered using that same metal piece, and just getting a color similar to that color I intend to paint the siding. This will at least keep water out of the walls, but that upper sheet's lower edge will still get moisture. I suppose I could paint that lower edge before applying it to seal the wood. I think this is preferred to just using caulk. However, I'm wondering if there is a specific material made for this purpose? Anyone know?

Note: I asked the clerk at the "big box" store about this, and the "kid" had no clue what I was talking about. I figured it was a waste of time to even ask, but I tried.....

Thanks

[DerbyDad03]

The "metal trim" you mentioned is call Z flashing. If you DAGS (images) you'll see pictures of it being used with T11.

You still want to use caulk between the flashing and the upper sheet. Will it last forever? I doubt it.

[HerHusband]

Install metal Z-flashing at the top of the lower sheet before you install the upper gable sheets. Z-flashing is usually stocked in most home centers.

The Z-flashing ensures that any water that finds it's way into the joint is directed to the outside of the wall. Do not caulk this joint, you don't want to trap water in the joint which could wick up into the upper siding.

Ideally, your T1-11 siding should have shiplap edges on the vertical sides. Basically, each sheet overlaps the previous sheet to keep out water. Otherwise, you should caulk the vertical joint to keep moisture from entering the wall at these joints.

Good luck,

Anthony Watson

[mancave]

Thanks

I visited a "real" lumberyard today, and he showed me the Z flashing. And yes, the sheets are ship lapped on the vetical sides. I can understand what you're saying about not caulking that horizontal joint by the Z flashing. But I think I'll apply some paint to that bottom edge of the upper sheets (same paint I'll use on the finished walls). Nothing lasts forever, but simple things like that can extend the life. For example, I always paint the eaves before installing rain gutters. Bare wood is just begging to decay, so a little extra paint and time insures a better protection for the wood.

[HerHusband]

If you have the time to prefinish that lower edge, it would be good insurance. I left a small gap (1/16") between the Z-flashing and the upper sheet. Water can drain out easier and I can still get in with a paint brush to paint that lower edge.

Take care,

Anthony Watson

[ChairMan]

if your really worried about rot, I'd use hardieboard. they have some that looks just like T1-11 and I'm using it to replace my T1-11 that is on my shed that has delaminated and started to rot

[mancave]

What did you use to get that 1/16 gap in there? I'm assuming cardboard or something like that, or else some thin steel or other metal plates. I know one cant just hold the sheet with a tiny gap like that before fastening it.

[mancave]

I tend to put more faith in plywood materials than any of that compressed sawdust stuff. A building I tore down some years back had a hardieboard siding and the stuff was all decayed. Just like every trailer house I've been around, it seems that the flakeboard they use on the floors just falls apart. A friend of mine is overweight, and lives in a trailer. He is constantly having to repair the floor because he will sit on a chair and the leg of the chair will go thru the floor, or he has just stepped in a spot and his foot went thru. I also see what happens when a piece of that (raw) stuff is left outdoors, it swells up from wetness and never goes back to the original thickness. I've already made a point not to use any compressed flakeboard, or any of that in my building. Plywood costs a few dollars more, but it far superior.

If I could afford it, I'd cover the building with aluminum siding, but that stuff is no longer affordable. The old redwood siding is also way too costly, although that stuff always seemed to hold up well, but paint tended to peel off of it. Seems these days that ugly vinyl siding is used for darn near everything. I absolutely hate the stuff. So that really only leaves me with the T11. I am looking to see if they make it with treated plywood. I was told it's available, but have yet to find it.

By the way, does anyone know why it's called T11 ???

[Gordon Shumway]

Holding the sheet with a gap and then fastening it is precisely the way to do it if the wall has been erected first.

The only alternative would be to sheet the wall prior to erecting it. Even then you still have to put the sheet in place with the proper gap before fastening it. Sheeting first would also allow you to ensure the wall is perfectly square.

Either way, easy peasy.

[hot-text]

Start with Tyvek First <

>

[ChairMan]

In news: [e-mail], [e-mail] belched:

you're confusing particle board/waferboard with hardie board. Hardie board is a concrete fiber material with a 30 yr warranty

I've replaced the T1-11 twice on 2 sides of my shed 16 x 20, west and south sides and each time it's delaminated/rotted in the last 15-20 yrs. YMMV

[Gordon Shumway]

Not all T11 is created equal. Some of it is made from 5/8" thick plywood. That's the good stuff. Other T11 is OSB. Some of that may only be 1/2" or maybe less. That's the not good stuff.

[hrhofmann]

I would not only paint the bottom of the sheets in the gable end top, I would also paint the bottom 3 or 4 inches on the inside in case water gets into the groove when wind-blown and creeps up the backside.

[ChairMan]

mine is the plwood type and it still sucks. It was primed and painted with quality paint the same paint that was used on my home. Home is fine, shed is rotting and delaminating I wouldn't buy ply T1-11 again if you paid me

[DerbyDad03]

I hate it when things creep up the backside.

[HerHusband]

To be honest, I didn't really plan it at the time. It just worked out that way as I was positioning the sheets. But any kind of thin spacer would work OK too.

Gable ends are usually just partial sheets anyway, so they don't weigh as much as you would expect. If you're using an air nailer, it's easy to hold the sheet with one hand and nail with the other (it's nicer if you can get someone to help hold the sheet). Otherwise, temporary spacers would work fine.

Anthony Watson

[HerHusband]

I don't remember what it was called, but I think you're thinking of that compressed fiberboard stuff. We had that on our old mobile home. It doesn't hold up well to moisture.

Hardiboard is different material. It's basically made of cement and wood fibers. It's extremely durable. I avoid it because it's heavy and hard on the cutting blades (makes a dusty mess when cutting). But I've used some of the hardi siding materials and they hold up well.

Old mobile homes used to use a particle board underlayment. We had that and it was terrible. It fell apart if it got the least bit wet.

Modern OSB is a completely different product. It's strong, and holds up to moisture at least as good as standard ply. The T&G OSB sheets made for floors have additional coatings to protect the sheets while exposed to weather during construction. Ours got soaked in rain numerous times over several months while we were building. No swelling or other damage at all.

OSB is actually better than standard ply for floors because it doesn't have any voids for a chair leg to poke through.

Hardi lap siding seems to be popular here in the Pacific Northwest, but vinyl is used a lot too.

You could always go with traditional cedar siding.

We used 5/8" rough sawn plywood (kind of like T1-11 without the grooves). Our plan was to install battens for the look of traditional board and batten siding. But, we were happy with the rough sawn siding by itself.

Anthony Watson