Correct Panel Spacing.
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Old Habits Die Hard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Proper Panel Spacing Can Save Time And Money. . . . . . . . . . . . . . . . . . . . . . . . 4
How Important Is Panel Spacing? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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Correct Panel Spacing
Old Habits Die Hard
A builder called today upset that he had been supplied OSB that was the wrong size. They measured
47 7/8” x 95 7/8” and should be 48”x96”. This “manufacturing defect” was going to cost him a lot of
money to correct the framing and result in him losing money. He proceeded to tell me that after decades
of building homes he knew what he was doing. This was bad material because the panels were missmanufactured because they didn’t line up with his stud layout and this was the manufacturer’s problem.
I explained that unless the unit was stamped, “Full Face”, the material supplied was the proper size
and would meet the required specs and standards and if he had spaced the panels the required 1/8”
everything would have lined up correctly. Then he told me he has never spaced panels and he didn’t know
anything about spacing panels. I explained that OSB producers stamp each panel with the “1/8” spacing
requirement” as well as “sized for spacing”. This was done to allow any expansion or contraction to take
place with changes in moisture conditions and to prevent buckling. When the call ended he was not happy
but I think/hope he understood where the problem was – The sheathing should have been spaced 1/8”
on all sides.
There a few things going on here so let’s see where things went wrong.
• The panels were not measured to determine the size before starting to frame the walls
• The walls were framed without allowing for spacing the sheathing
• The panels were installed without the required 1/8” spacing
• The studs were laid out and framed based on a full face 48” but still no allowance for spacing the
panels. If “Full Face” 48” panels had been spaced he would have been off the studs the other way.
How to prevent this kind of issue
1. First of all – always measure products (any product) so you can make adjustments if necessary.
Remember the old saying “measure twice and cut once”. Frame according the material you are using
and “not the way you always have”. Building practices and products change and methods need to
change along with them.
2. Always, always space wall and roof sheathing (plywood and OSB), 1/8” along all edges. Wood
expands and contracts with changes in moisture conditions. Without that required spacing you may
have buckling issues. I suspect that over the years many issues, such as siding and windows were
blamed as defective product and/or poor installation when the lack of spacing the sheathing may
have been the issue. A report based on job site inspections by the APA (The Engineered Wood Assoc)
showed “not allowing the spacing” was in the Top 5 Framing Errors in North America.
3. Watch this APA video on spacing sheathing it’s REALLY GOOD! http://www.youtube.com/
watch?v=y0VaZw1E2Xg
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Correct Panel Spacing
Proper Panel Spacing Can Save Time And Money
“It’s Cheaper To Fix Issues In The
Beginning Of Any Process Than At The
End”
When structural panels are not spaced properly and
moisture conditions change some problems can arise.
Construction companies have been dealing with the
issue of panel expansion for years and they should
take the time to educate the installers in easy steps to
prevent or reduce future issues. Space the panels using
a nail as a space guide. It’s easy, fast and the panels are sized to allow for that 1/8” spacing.
Of course every effort should be made to avoid the subflooring panels wet, but the reality is, panels may
see rain before the home is dried in. When moisture conditions increase, wood will expand and adjust to
the surrounding moisture conditions. Leaving that 1/8” space between edges means it acts as a “mini
expansion joint” and the panel can expand and move without causing deflection or buckling.
How Important Is Panel Spacing?
Question
How important is allowing for the 1/8 inch space with 4
x 9 x 1/2 material when sheathing an exterior wall?
Larry, Portland Oregon
Answer
Panel spacing is absolutely essential. Your OSB wall
sheathing will expand or contract as it adjusts to the
ambient conditions of your climate zone. Insufficient
spacing between the panels can result in buckling and
expensive call-backs.
Using 10d nails as a spacer will help provide the
required spacing and speed up your installation process. Consult the manufacturer’s instructions as well
as those set out by your design professional when installing OSB wall sheathing.
Correct Panel Spacing Prevents Buckling
Plywood and OSB paneling expands and contracts as it adjusts to the moisture content of the building
site. Unrestrained by fastening and framing, panels can move an average of 1/8 inch as they acclimatize.
Correct spacing between panels when framing will absorb most of this expansion, but where insufficient
spacing or dense nailing patterns prevent movement, a net expansion of floor and roofing decks may
result in unevenness or buckling.
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Correct Panel Spacing
The cumulative effects of panel expansion can also result in walls and floors that aren’t straight and door
and window openings may be affected in both interior and exterior walls. The resultant gaps in the building
envelope compromise energy efficiency. Remember; “Energy Savings start with the Framing™.”
Prevent Buckling
When adequate spacing between panels is not present, buckling may occur in walls and roofs and may
also result in uneven flooring or roofing. Panel spacing of 1/8-inch is recommended and, in most cases,
required to provide installers a means of minimizing the potential for panel buckling.
Although buckling will not adversely affect panel performance, it has a negative aesthetic impact and can
cause related problems. While proper panel spacing should be a part of every build, there are certain
circumstances under which the risk of buckling increases. According to the APA document X480C, these
include:
• Shear wall or diaphragm applications with edge nail spacing 4 inches o.c. or closer
• Use of 3-ply plywood panels with a face grain parallel to supports (i.e. walls)
• Panels installed within a few days of their manufacture
• Extended rainy weather where panels may become saturated with water
• Panels that have not been allowed to acclimatize properly
Under these conditions, the 1/8-inch panel spacing may not suffice. Buckling can be minimized by
allowing panels (especially those which have just been manufactured) to acclimate to their new conditions.
Store panels on-site under the conditions outlined in the APA guidelines prior to the build.
If there is no time to allow for acclimation, consider increasing panel spacing to ¼ inch. In instances
where nail spacing is 4 inches o.c. or closer, the panels will not be able to expand, rendering the 1/8inch panel spacing ineffective in preventing buckling. Where possible, framers should opt for 12 or 24
o.c. nail spacing initially and then leave the panels to absorb moisture and expand. Once the panels
are acclimatized, the nailing patterns must be completed or you will not have the structural properties
needed.
Preventing Net Expansion In Larger Buildings
Structures longer than 80 L/F must have expansion joints built into them to allow for expansion and
contraction. The APA document U425 indicates that with flooring, gaps of ¾ inch must be created between
panels at the designated joint intervals. Nailing and fastening of panel ends can be left until the wood
has acclimatized to allow for expansion. With roofs, the APA recommends sheathing large roofs in 80-foot
sections… “omitting a roof sheathing panel (in each course of sheathing) between sections. This provides
effective temporary sheathing joints.” Once the panels have acclimatized, the missing panels can be
trimmed to size and installed.
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Correct Panel Spacing
Wood Grain Directions
Make sure plywood is installed with the grain in the right direction. When plywood is incorrectly installed
it can lead to soft spots, squeaky floors, buckling or (worst case scenario) structural failure. Plywood
and OSB sub-flooring must be installed with surface grain at right angles to the joists. Plywood or OSB
roof sheathing must be installed with surface grain at right angles to the roof framing. Don’t install
panels parallel to the supports. Span ratings are based on the proper installation of panels, so ensure
that yours are installed according to your local building code, design professional’s instructions and the
manufacturer’s installation instructions.
Always ensure the supports (joists and roof framing) are level and straight and take corrective action
before installing any panels. Installing your plywood and OSB wood panels with sufficient panel spacing
and with the grain oriented in the right direction will ensure perfect walls and roofs, an efficient building
envelope and even flooring that doesn’t squeak.
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