I am building a 8x12 playhouse and am planning to install 3/4" plywood
subfloor. I am following a book for plans & directions. Now, I would
have installed the 3 8x4 plywood sheets one next to the other (8ft
dimension of plywood aligning to the 8ft side of shed) to cover the
8x12 area.

However the book suggests to cut one of the sheets into half (4x4) and
then use one 4x4 and then an 8x4 (8 ft dimension of plywood aligning
with the 12 ft side of shed) on one side, and reverse on the other (ie.
first the 8x4 and then 4x4).

I am sure there is a good reason for it, but it does not say why.
Could someone explain?

Also, what kind of tolerances are "acceptable" when building something
like this? That is, if the size of floor or walls is within 1/8" inch
it is OK or 1/4" inch etc. Is there any particular dimension that
needs to be more exact (e.g. height of walls has to be more exact than
size of floor)?

Thanks

AK

wrote:

....snip...

I am sure there is a good reason for it, but it does not say why.
Could someone explain?

Simply to stagger joints to avoid one joint all the way across...it'll
tie the whole floor structure together more solidly than w/ a continuous
break.

Also, what kind of tolerances are "acceptable" when building something
like this? That is, if the size of floor or walls is within 1/8" inch
it is OK or 1/4" inch etc. Is there any particular dimension that
needs to be more exact (e.g. height of walls has to be more exact than
size of floor)?

1/8" is a good target....it's significant to make sure your spacing
isn't off enough to have to trim "just a smidge" off the finish
materials on any surface to make it simple...it's a real pita if the
ceiling height turns out to be 7' 11-1/2", for example and every wall
panel has to be trimmed to make it fit.

Duane Bozarth wrote:

wrote:


...snip...



I am sure there is a good reason for it, but it does not say why.
Could someone explain?



Simply to stagger joints to avoid one joint all the way across...it'll
tie the whole floor structure together more solidly than w/ a continuous
break.



Read his description again. 8' x 12' floor, 3 sheets with the 8' side
along the 8' joist. As long as the joist run along the 8' side, there
will be no joint to stagger. No continuous break. Lay three sheets,
square it up, and nail it down! Otherwise, you are correct, you want to
stagger your joints.



snip

wrote:
However the book suggests to cut one of the sheets into half (4x4) and
then use one 4x4 and then an 8x4 (8 ft dimension of plywood aligning
with the 12 ft side of shed) on one side, and reverse on the other (ie.
first the 8x4 and then 4x4).

I am sure there is a good reason for it, but it does not say why.
Could someone explain?

This approach doesn't make much sense to me. I assume the joists are
running in the 8 foot direction. Laying three sheets side by side will
give you joints between the panels directly over joists, so the sheets
will be fully supported around all their edges.

Putting the sheets the way you described will give you one unsupported
joint between the sheet edges along the middle of the floor for the
whole 12 foot length.

It could be this practice comes from floors with larger areas where
single sheets won't span the whole floor, and you have these butt
joints between the ends of sheets anyway.

On 7/26/2005 1:46 PM mumbled something about the following:
I am building a 8x12 playhouse and am planning to install 3/4" plywood
subfloor. I am following a book for plans & directions. Now, I would
have installed the 3 8x4 plywood sheets one next to the other (8ft
dimension of plywood aligning to the 8ft side of shed) to cover the
8x12 area.

However the book suggests to cut one of the sheets into half (4x4) and
then use one 4x4 and then an 8x4 (8 ft dimension of plywood aligning
with the 12 ft side of shed) on one side, and reverse on the other (ie.
first the 8x4 and then 4x4).

I am sure there is a good reason for it, but it does not say why.
Could someone explain?

Also, what kind of tolerances are "acceptable" when building something
like this? That is, if the size of floor or walls is within 1/8" inch
it is OK or 1/4" inch etc. Is there any particular dimension that
needs to be more exact (e.g. height of walls has to be more exact than
size of floor)?

Thanks

AK


I'm assuming they're wanting you to lay the plywood like such
(make sure you use a fixed font to view this)

+----+----+ instead of +---------+
| | | | |
| | | | |
+----+ | +---------+
| | | | |
| | | | |
| +----+ +---------+
| | | | |
| | | | |
+----+----+ +---------+

on 16" on center floor joists.

--
Odinn
RCOS #7
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rot13 to reply

I'm with Tim on this one.

In "regular" contruction, it is good preactice to stagger the joints, but
that need goes out the window when you can span the room with a single
sheet. For this appplication (Sheet-sized room, in a playhouse) it just
doesn't matter.

Cheers,

Steve



wrote in message
ups.com...
wrote:
However the book suggests to cut one of the sheets into half (4x4) and
then use one 4x4 and then an 8x4 (8 ft dimension of plywood aligning
with the 12 ft side of shed) on one side, and reverse on the other (ie.
first the 8x4 and then 4x4).

I am sure there is a good reason for it, but it does not say why.
Could someone explain?

This approach doesn't make much sense to me. I assume the joists are
running in the 8 foot direction. Laying three sheets side by side will
give you joints between the panels directly over joists, so the sheets
will be fully supported around all their edges.

Putting the sheets the way you described will give you one unsupported
joint between the sheet edges along the middle of the floor for the
whole 12 foot length.

It could be this practice comes from floors with larger areas where
single sheets won't span the whole floor, and you have these butt
joints between the ends of sheets anyway.

Thanks all for your replies. They are most helpful

Regards

wrote:

Thanks all for your replies. They are most helpful

I'll note in addition to Odinn's nice drawing, that doing it the way on
the left eliminates the 8-ft alignment along the length of a joist
(assuming the joists are run shortwise, of course) in lieu of two 4-ft
sections. This makes layout alignment slightly less critical.

wrote:
...

However the book suggests to cut one of the sheets into half (4x4) and
then use one 4x4 and then an 8x4 (8 ft dimension of plywood aligning
with the 12 ft side of shed) on one side, and reverse on the other (ie.
first the 8x4 and then 4x4).
...
I am sure there is a good reason for it, but it does not say why.
Could someone explain?


Plywood subflooring is typically laid with the face grain accross
the joists rather than parrallel to it. This is because plywood is
15% stiffer accross the face grain, than parrallel to it.

On most 4 x 8 plywood the face grain runs parrallel to the long
edge so the plywood is laid with the 8 foot edge accross, that
is to say perpendicular, to the joists.

--

FF