They’re beautiful, the wood floors we do for our clients --fine functional furniture. I love that our clients treasure them and want them to be perfect.
But, when all the dust has cleared and the last guest has gone – at the end of the day -- you’ve got to feel good walking all over them, because they’re your floors. That’s what they’re for. You have to use them. What else will you walk on?
I know you want them to be beautiful and to stay that way. You can love them and care for them or simply get along with them, but they’re still your floors and they’re what you’ve got to stand on. So, unless they last, how good are they, really?
We can make them look like a work of art, but they don’t belong in a frame on the wall. We hope you’re happy using them as they were intended -- like no other piece of furniture or woodwork in your home.
It’s pointless to worry how they look in this light or that. The occasional blemish or defect occurs in all natural products. Those are character. Every wood floor – including yours – will have them. Character makes them unique. Site finished floors are hand worked, so they will have even more character.
What you really need to worry about is how long your floors will last. How are they to clean – and stay clean? How good will they look in 5 years or 25? How will they take the abuse you and your family (and friends) will give them over time? Will you still love them then? Those are the most important issues to keep in mind. The true beauty of real wood floors is how they look – lived on. Their beauty is not skin deep. It runs all the way through.
We all love happy customers – especially me. Just know we work the hardest on the crucial qualities of your floor. The longer you have your floor, the more you’ll appreciate our work.
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OSB (update) February 2009
Some time ago I asked an old friend to review a proposed article I had written on OSB and its performance as a subfloor and/or underlayment under wood flooring. I knew I would get an honest and accurate critique of its contents especially in light his many years of experience working with highly reputable and internationally acclaimed wood products companies. He has studied numerous wood panel operations, including several OSB and plywood plants, in his role as research director and quality manager for two large wood panel producers.
Due to the intense schedule of his new digs at PSU, it was a few months in coming. When it did, it was well worth the wait. My experience working with and over OSB and that of my many colleagues in the wood flooring business tells one story, but I wanted an opinion from a researcher and scientist , a highly qualified and experienced QC expert from manufacturing. I wanted help understanding the WHY and HOW behind the many and diverse OSB quality levels. I reasoned that someone “in the known” who had worked for years at the manufacturing level could help explain some of the things my friends and I have experienced when installing wood flooring to OSB. Here is his response:
"Variability is an issue with OSB quality. The forming machines in the plants, the moisture content of the flakes out of the dryers, the presses, the resin type and application rate, and the resin quality itself as it comes from the resin supplier are all variable. Some companies attempt to control this variation, and do a fairly good job of it; others pay little or no attention to it. They all have QC testing of product at the plant level, but statistically the sampling is inconsequential; thus, the individual panels the contractor obtains may or may not have the minimum properties certified by the grade stamp.
This is the reason why some OSB installations come out great, while others (with OSB of the same supplier and grade) may fail. OSB just doesn't have the inherent consistency of plywood. Having said that, there are problems with plywood quality control as well, but generally, plywood producers are fairly liberal with their resin applications, and the processing of plywood is less complex than OSB, so there are fewer potential "problem points" with plywood."
Charles D. Ray, Ph.D.
Associate Professor, Wood Operations Research
The Pennsylvania State University
University Park, PA 16802
Formerly Corporate Quality Assurance Manager, LP Corporation.
|One Final Comment:
I’ve been told by an industry “insider” that the better OSB makers CURRENTLY hold their “flooring-grade” OSB products to a higher standard than ¾” OSB rated sheathing. This should mean that their “flooring-grade” OSB will demonstrate less variability than standard OSB products. While there is no proof of this, at least it’s something.
May 1, 2008
OSB or Oriented Strand Board,
is the name applied to paneled products (similar to plywood)
made from small cut (usually compressed) pieces of wood or
strands arranged or oriented in opposing directions (typically
in at least 3 opposing layers).
I’ve seen trade
associations refer to OSB and waferboard as “panel products
made from strands or wafers of various different wood species
bonded together under heat and pressure using a waterproof
phenolic resin or equivalent waterproof binder.” When you
look deeper, you see the binding adhesive referred to more
specifically to as phenol-formaldehyde resin.
On a personal note, I feel the
use of the term “waterproof binder” in the description
somewhat misleading. One gets the impression all OSB is
weatherproof. It’s not. I might go as far as using the term
“water resistant” when referring to some special types of
OSB, but certainly not waterproof. Formaldehyde is extremely
responsive to moisture by nature. So is wood. Modifying the
resin and sealing the wood can make the product more water
resistant. Coating & sealing the faces, edges and ends can
make it repel moisture. But, I have a hard time believing it
can be classified as “waterproof”.
I’ve noticed trade
associations and others frequent use of the term “commonly
used” or “successful uses” when referring to
applications for OSB, composite board or waferboard as a
subflooring material for hardwood flooring. Why not declare it
“rated for use” or “recommended for use” as a
subflooring material for all hardwood flooring. If all makes
and brands of OSB and composite board are without deficiency
as a subflooring material under nailed down wood flooring, why
not say so?
RATINGS & STANDARDS
OSB or oriented strand board
(like most things) comes in a variety of different qualities.
Standards vary depending on intended use as well as intended
destination. Many of these appear to be changing year by year,
especially in the USA. OSB manufactured in and intended
for use in the USA may be rated, but at best will conform only
to “voluntary product standards” compared to that intended
for use in Canada, which must conform to set CSA (Canadian
Standards Association) product standards.
AN INDEPENDENT STUDY
Some independent testing was
conducted at the collegiate level a number of years ago at the
request of and paid for by one of our wood flooring
associations. It was to determine, among other things,
OSB's feasibility, suitability and overall reliability as
a subfloor or underlayment for solid wood flooring. Without
getting into a whole lot of specifics and details about the
sampling methodology, testing procedures or the findings, the
results were such that it caused the wood flooring
associations to approve (more or less) the use of ¾-inch-thick
OSB as a subfloor or underlayment material for hardwood
flooring in the absence of other more definitive data or
restrictive constraints pertaining to a specific installation
specification. I think it’s interesting to note that given
the same circumstances, 5/8” plywood remains approved as a
subfloor for solid nail down wood flooring by these same
WOOD FLOOR STANDARD SUBFLOOR/UNDERLAYMENT
I would like to go on
record as saying once again -- I personally recommend as a
MINIMUM subfloor for solid nail down wood flooring ¾”
underlayment grade plywood (minimum 7 ply construction) glued
& screwed or glued & nailed to 2 X 12 or better joists
set 16” on center or closer. This is only if the flooring is
set perpendicular to the joists. If the wood flooring is to be
set parallel to the joists OR if the flooring boards have an
average length of under three feet OR if the flooring is to be
laid in a pattern (parallel with or diagonally to joists) OR
if the flooring is to feature borders, inlays, insets or other
unsupported objects, a minimum additional ½” of
underlayment grade plywood (minimum 5-ply construction) should
be installed by ring shank nails or screws over the ¾”
plywood subfloor insuring that all underlayment and
subflooring seams are offset by a minimum of 18 inches.
One strong caveat to OSB’s
use as a subfloor or underlayment for hardwood flooring that
came out of the study was that the OSB must not be allowed to
“get wet” prior to its installation or prior to the
installation of the hardwood flooring over it. This disclaimer
came as a result of observations made during testing that
showed a substantial reduction in the holding power of
fasteners driven or shot into the OSB when it was wet or after
it had been saturated with water and then allowed to dry.
These observations also showed that the OSB tested exhibited a
tendency to swell more at the seams when allowed to get wet.
This was particularly pronounced along cut edges. Further,
this swelling did not appear to subside significantly, once
the material was allowed to dry. Finally, these “swollen”
areas showed a marked reduction in holding strength compared
to other sections of the OSB panels.
Since OSB has come onto the
market (roughly 25 years at this writing), I have enjoyed both
good and bad experiences with hardwood flooring installed over
it. I have rarely seen out-and-out failures, but on a number
of occasions have observed what I consider to be below
standard results partially or entirely due to the use of an
OSB product, no doubt of a lower or inferior grade compared to
some others on the market.
MY CONCLUSION – Caveat Emptor
To the best of my knowledge at
this writing, the resin formulations and the processes
utilized in the fabrication of OSB and composite panels vary
considerably by manufacturer and as a result the quality and
suitability of the panels they produce for use as a subfloor
or underlayment for hardwood flooring.
Let me quickly make two
comments about this. To my knowledge, at this writing, and as
a general rule, the majority of “industry standard” OSB
manufactured in the good ole USA still does not carry a
grading stamp that specifies or qualifies its functionality
specifically or indicates the specific formulation of resins
utilized in its manufacture. Rather, panels are “performance
rated” allowing manufactures to toy around with the
methodologies, procedures and products utilized with and in
Currently, the Canadians hold
themselves to a bit higher standard. The OSB manufactured
there must meet CSA standards, unlike OSB products made here
that have only to meet “voluntary” levels or standards of
manufacturer. Of course, this alone does not insure a better
product – just a more consistent one.
A QUICK STORY
A couple years back one of my
installers (let’s call him Bill – not his real name)
called me on my cellular phone and said, “Boss, we have
problem.” Bill was working on a high end residence where he
had just finished installing a border and was preparing to put
down the initial portions of an inlay. As Bill began dry
setting the interior inlay, he was not happy with the
appearance of a couple of flooring planks he had already
nailed down on the perimeter border. He began prying up the
disagreeable boards with his crowbar when he noticed that they
popped up way too easily. He reached down with his bare hands
and easily pulled up several more planks. All of the boards he
removed still gripped their fasteners. There were plenty of
nails to secure the boards. They should have held firm.
Removing the boards, even with a crowbar, should have been
difficult. But he was using his bare hands and had no
Bill said the face ply of the
subflooring looked like plywood so he assumed that’s what it
was. He went down below the subfloor and looked up. The bottom
face of the subfloor also looked like plywood. Bill was
confused. He had never seen a nailed down wood floor pull up
so easily. After searching around the house, he found a couple
of large holes had been cut through the subflooring in the
kitchen area, probably to allow for plumbing or electrical
lines. Using a flashlight he saw what looked like a
particleboard core sandwiched in between the top and bottom
layers of the subflooring. That’s when he called me.
I finished what I was doing as
quickly as possible and drove to the jobsite. Sure enough, I
could pull up virtually any board Bill had nailed down using
just my bare hands. I was appalled. I immediately called our
primary contact for the project -- the homeowner and advised
him of our concerns. To my surprise, the homeowner, also a
general contractor (a commercial builder) told me he had
already noticed what his builder was using as subflooring.
But, when he questioned him about it, his builder told him
that his lumber supplier said the product was now rated for
use under hardwood flooring. Our client said he didn’t think
that it was right, but chose to go with what his contractor
had elected to use.
We refused to warrant our floor
over the existing subfloor and pulled off the job. In the
meantime, the builder contacted his lumber supplier and they
in turn contacted their subflooring supplier. The builder said
his lumber supplier called the product a composition board and
that it was rated for use as a subfloor under hardwood
flooring as was standard OSB material. I told him, it didn’t
matter to us how it was rated or by whom, if we could pull up
our flooring boards with only our bare hands, we were not
going to install our wood flooring over it.
The owner and builder waited
for several weeks to have the subflooring inspected and tested
by the vendor’s supplier, but to no avail. Finally, the
owner had the entire subfloor removed and replaced at his own
expense. He may have made his builder pay for it later, I
don’t know. The new subflooring the builder installed was a
good ¾” 7-ply ACX plywood. This time however, another ½”
5-ply plywood underlayment was installed on top. From that
point on, things went extremely well and in the end, our
customer got a superlative wood floor on a sound foundation
FINDING A GOOD OSB PRODUCER
I’ve become aware of several
“quality oriented” OSB manufacturers attempting to
differentiate their products from lesser products by using
names that sound like they’re superior (and no doubt
charging more for them). Of course most of us are aware that
this might be nothing more than a marketing ploy. “New and
improved” has sold an awful lot of product over the years.
Without indicating on the panels just “how” one
manufacturer’s product is superior to others, I don’t see
On a positive note, I have
noticed that some “principled” OSB manufacturers (who also
make plywood) do not recommend their OSB for subflooring under
hardwood flooring. They indicate instead the use of their
plywood products for hardwood flooring subfloors. I
congratulate them on that. Still, I know, as do they, that
many builders simply opt to buy OSB panels for use where
hardwood flooring is going to be installed regardless of
anything but price. They can’t force their customers to
follow their recommendations.
WHO CHOOSES TO USE OSB
An impromptu polling of many of
our customers found that the normal purchaser of OSB panels
was a general contractor, developer or their purchasing agent.
What was surprising was that the purchaser had little
knowledge about the overall “quality” or “suitability”
of the OSB they purchased for use under hardwood flooring.
They purchased what their lumber or materials supplier
suggested or what was available at a given price point
befitting the budget. By the time a wood flooring contractor
came onboard or visited the site, the OSB panels were in place
(and in our part of the country, had often been rained on
WHY CHOOSE OSB
Let’s quickly pop the “OSB
is greener” bubble. I’m not buying into it. I know the
size trees it takes to make OSB vs. plywood and I know the
chemicals going into both products. It makes more $$$ for the
lumber companies I’ll grant you. Like the over-used saying
goes…at the end of the day and like the once popular, now
ex-Seattle athlete playing back East put it: “It’s not
about the money. It’s all about the money.” Now I have
nothing against making money. I wouldn’t own a business for
profit (well it does sometimes) if I did. I simply think the
more we know about what we buy the better our buying
decisions. It really disturbs me to see a small wood flooring
contractor eat an installation simply because a poor choice
was made (not by him) on the proper subfloor.
MY OWN TESTING ON EARLY
VERSIONS OF OSB
Back in the days when many of
the US plywood manufacturers were developing their own
versions of OSB, I tested several different products from a
number of different companies on their behalf and at the
request of one association. What I discovered still intrigues
Virtually all the products I
tested not only proved the equivalent of 7-ply or better
underlayment grade or marine grade exterior plywood, they were
far superior. Water didn’t seem to faze them. Left for weeks
submerged in water, test samples show no signs of moisture
impregnation even when cut or with fasteners driven into them.
Each retained fastener holding strength even when left to soak
in water for weeks (months in one case). My own personal
assumption is that the resins used in those early products
proved too expensive for production run products (at least for
the average manufacturer).
It wasn’t long before I noted
the quality of OSB products produced by most manufacturers
failed to equal or even come close to those initial test
results. The MDI resin formulations I was told was utilized in
the manufacture of those early products quickly degenerated
into resins formulations of lesser resolve. I found that
formaldehyde-based resins formulations were quickly adopted by
almost everyone. The pendulum had swung way backward in my
Formaldehyde has long been
utilized as an inexpensive (yet generally effective) resin
base for many wood composites. Unfortunately, like wood, it is
also extremely moisture sensitive
SOME BASIC FACTS
A dry (never allowed to get
wet) ¾-inch-thick “industry standard” OSB panel installed
by gluing and nailing (or screwing) over 16” on center
joists or closer, will provide adequate holding power for
nailed down solid wood flooring -- in some instances. However,
more movement and loosening of flooring boards must be
expected over time compared to the same or similar
installation over “industry standard” ¾” 7-ply plywood.
This is particularly true over I-joists and/or where joist
spans exceed 16 feet.
Significant swings in relative
humidity will subject OSB subflooring or underlayment to even
greater stresses when solid wood flooring is nailed into it.
Some common examples of this might be found in vacation
properties, homes with in-floor heating or wood burning
stoves/fireplaces, and structures located in especially moist
or especially dry regions. The most profound effects are
generally noted in areas where the indoor atmosphere
fluctuates significantly (moist to dry or dry to moist with ±
40% or more relative humidity) between seasons.
OSB panels constructed with
many of the more commonly used resin formulations should not
be counted upon to adequately withstand the severe additional
stresses placed on them by wide swings in moisture content
within wood flooring. Once completely flooded, wood flooring
installed over OSB should under most circumstances be
considered “ruined” and not capable of drying and
resurfacing as with comparable installations of solid hardwood
flooring over solid wood subflooring or plywood subflooring.
For this and other reasons
(e.g. potential for off-gassing), OSB must generally be
considered a “poor choice” for subflooring or underlayment
over in-floor radiant heating systems.
WHAT TO LOOK OUT FOR AND WHEN
Swelling of OSB panels along
the seams or along cut edges represents evidence of an
inferior subflooring material and should be given strong
consideration for replacement prior to installing any solid
wood flooring. Flattening the raised or puffed edges of the
OSB by sanding or other methods will become necessary to make
such a subfloor installation even workable. Still, the
fastener holding power in affected areas (if not the entire
panel) must be considered highly suspect. To my knowledge, no
conclusive testing has ever been conducted (or at least made
public) on the overall fastener worthiness in water damaged
STAPLES AND OSB PANELS
Some evidence exists that the
“all or nothing” holding characteristics of staples
affords some enhanced properties when used to fasten solid
wood flooring to OSB or wood composites. A portion of this may
be due to the overall mass or bulk of most staples in
comparison to that of nails, cut fasteners or cleats. There
appears to be a reduced tendency for staples to “fracture”
or “crumble” the fibers of composites when they are shot
or driven into them compared to what can sometimes happen with
larger fasteners. Unfortunately, the holding power of staples,
nails, cut fasteners or cleats appears to be universally and
dramatically assailed when the composite has been damaged by
water or exposed to moisture.
SOME FINAL WORDS
It is important to note that
the foregoing observations are based on OSB and composite
products previously and currently (as of this writing)
available on the market in North America -- primarily the USA.
Not all OSB panels have proven, at least to this observer,
even intermittently deficient as subfloors under hardwood
flooring. Further, construction products manufacturing of
these types of products should be considered a “real time”
effort. As advances in resin formulations, processing
procedures, etc., come about or are discovered by these firms,
real and substantial changes can occur. Movements away from
certain processes, techniques or resin formulations
(especially given the primary grading authority’s stance of
“performance rating” such products) could happen without
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