I've looked for a definition on the web and it seems that T1-11 is
hardboard. But I've also seen it called plywood. Which is it?
I thought they were very different. Plywood is iiuc 3 or more layers
of wood, where each layer comes from putting a log on a big lathe and
taking off a continuous strip of wood, each layer deeper into the log
for every rotation of the lathe. That's why one sees a repetitive
pattern on plywood, because if that part of the tree is 16 inches in
circumference, every 16 inches one sees a different level of the same
Hardboard otoh in wikipedia is described "Hardboard, also called
high-density fiberboard, is a type of fiberboard, which is an
engineered wood product. It is similar to particleboard and
medium-density fiberboard, but is denser and much stronger and harder
because it is made out of exploded wood fibers that have been highly
compressed. Consequently, the density of hardboard is 31 lbs. or more
per cubic foot and is usually about 50-65 lbs. per cubic foot. It
differs from particle board in that the bonding of the wood fibers
requires no additional materials, although resin is often added.
Unlike particleboard, it will not split or crack. It is used in
construction and furniture."
I think T1-11 is heavier than plywood of the same thickness. It seems
to be hardboard. Right?
My cabin built in '97 used this material as exterior horizontal sidng.
T1-11 is hardboard. Ours has natural wood color with grains Ver very
hard. Driving nail on it is not easy. I used screws when I had to hang
or attach something. It came with a 20 year warranty for color and still
it looks like just installed. Better fire resistant than plywood as well,
MODERN t 1-11 is usually OSB with a layer of ply on the pretty side, or
sometimes even a 'prefinished' plastic skin. REAL t 1-11, like we used
back in the stone age, is indeed plywood. As a kid I humped plenty of
it, in full 1/2" and 5/8" thicknesses. No idea if the real stuff is
available any more, since I no longer swing a hammer for money.
T1-11 is either plywood or OSB (Oriented Strand Board) with grooves cut
vertically to simulate wood planks. The term "T1-11" apparently refers
to "Texture 1-11", a description of its appearance.
Plywood is, as you state, several layers of wood glued together. The
grain is perpendicular in alternating layers, making the sheet very
stable and resistant to size changes due to humidity.
OSB is "flakes" of wood glued together. The grain of the flakes is
alternated in different layers to make the panel stable, similarly to
The T1-11 I've bought has been slightly lighter than the same thickness
plywood because of the missing wood in the grooves.
Hardboard siding is available with pressed-in textures that look a lot
like T1-11, but it's more fragile and more easily damaged by water. I
once had a house with this type of siding, and it's a lot of trouble.
Fiberboard comes in LDF (Low Density), MDF (Medium Density), and HDF
(High Density). Pegboard is typically LDF, painted or hidden parts of
cabinets is typically MDF, and Masonite is a common brand of HDF.
FYI - The botton of the door on my 25+ year old shed was rotted so I needed
to replace it. A few trips to the home centers showed 2 products that
looked similar. One was a hardboard but the other, the ONLY one actually
labeled T1-11, was plywood which is what was on my shed. I purchased the
latter. It is in fact plywood and matched the old one perfectly.
As others have said, T1-11 is plywood. It comes in 3/8" or 5/8"
thicknesses and either 4" or 8" wide options. Hardboard siding has
been manufactured to look like T1-11, but it is in fact, hardboard
siding with a finish "like" T1-11. Even Hardipanels come with a
T1-11 finish, although they call it Sierra 8. That doesn't make it
OK. so what do you call the stuff on my house , a tract home built
in 1971, which has siding that "looks" like T-111 but is
definitely not plywood (like the other posters picture). It is
some kind of composition I would compare to thick cardboard. If
allowed to get wet, it swells like a roll of paper towels would.
And it does not hold a screw very well at all.
Here they offer an additional option to the 4 & 8" O.C. grooves, they offer
it with a 12" O.C.
They also offer it in yellow pine, or fir, with fir being more expense.
24 years ago, I finished my place with 5/8", 8" O.C. fir. I have stained it
twice. It still looks fantastic.
The first time I stained, I used a colored transparent stain. The last
time, I used a solid stain. The transparent stain does not hold up to our
Midwest elements as well as the solid stain.
When you say : "Or do you mean pignmented stain, that these houses were
done in, that
seems an awful lot like paint to me?" You very well may have paint, and not
stain. I've seen pre-painted masonite, that's how it leaves the
I will never use exterior paint again. Exterior stain is the way to go.
Stain will not peel or flake like paint, it appears to just weather.
If it is 12" OC, then it is not T1-11. That particular pattern is
called Reverse board and batten. It will look like T1-11, but the
spacing changes its designation. T1-11 is ONLY 4" or 8" OC. I am
not trying to nitpick here, just educate.
You're about the only one to understand the properties and description of
Here are two of my T1-11 'pet projects; :
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