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Flooring Underlayment - Types and Uses
Introduction
This article discusses the different types of underlayments and how they are
used for the installation of laminate flooring and some floating wood
floors. A question we hear quite a bit is, "what is the best underlayment to
use when installing a laminate floor"? Over the past few years, the
manufacturers have made it a little difficult by introducing various types
of underlayments with different features. The object of this article is to
give you a general idea of what is available, and what may be the best
choice for you.
When & Why are Underlayments Required?
Underlayment is required anytime you will be installing a laminate floor, or
a floating engineered real wood floor. Both laminate flooring and floating
wood floors are installed using a "free float" method, where they are not
actually attached to the sub-floor, instead the boards are attached
together. The underlayment gets laid down over the sub-floor, the flooring
lays on top of the underlayment and gets attached together either by gluing
the tongue and groove, or by locking the boards together if it is a
"no-glue" type product.
Well that answers the when part of the question, now let's answer the why.
The function of the underlayment is to absorb some of the minor (very minor)
imperfections in the sub-floor, to help deaden sound when walking on the
floor since the flooring is not attached to the sub-floor, and to slightly
(very, very slightly) soften the feel when the floor is walked on. Let me
clarify one very important point that is a topic of discussion every time
underlayment is brought up. Underlayment for laminate and floating wood
floors should not be confused with padding for carpet. If you think you can
buy a better or thicker underlayment and the floor will feel softer, you are
wrong. Unfortunately there are some salesmen in the industry that are
accustom to selling customers upgraded carpet padding, and now they are
using the same sales tactics with flooring underlayments.
There are different types of underlayment available which we will discuss in
the next few sections. It is important to mention that when choosing an
underlayment for your new flooring, you must use underlayments that are
offered, or approved by the manufacturer of the particular flooring you are
interested in. The four basic underlayments offered in most cases are:
Standard Foam - a standard foam usually 1/8" in
thickness without any moisture barrier attached
Combination Foam/Film - sometimes referred to as
"Combo" underlayment - most of the time identical to the Standard Foam
except there is a moisture barrier attached to the bottom
Modified or Upgraded Underlayments - these are
available in different thickness and densities, usually constructed of a
higher density foam, rubber, etc.
Solid Cork - Used only when required for maximum sound
reduction. This product is generic and used mostly in condo buildings
because the condo rules specify it be used.
Standard Foam Underlayment (Without Attached
Moisture Barrier)
What is it? - The most common underlayment is the Standard Foam
underlayment. Most manufacturers have their own fancy name for this
underlayment, but essentially they are all the same. This underlayment is
simply a thin foam padding, for lack of a better word, usually measuring
about 1/8" thick. The roll sizes vary from manufacturer to manufacturer, as
does the price. We have seen manufacturers offer this underlayment in rolls
ranging anywhere from 100 square feet, to 1,300 square feet. Depending on
the size or your flooring project, you may want to take advantage of the
larger rolls if they are available. In most cases they are priced slightly
less per square foot because you are buying in bulk. The standard
underlayment offers a more than adequate level of topical sound reduction,
comfort, and sub-floor correction.
Where is it used? - Since Standard Foam underlayments do not have a moisture
barrier attached, they are typically used where there is no possibility of
moisture coming up from the sub-floor . In most cases, this would be over a
plywood sub-floor, however there are some instances where they would also be
used over a concrete sub-floor. This would be for example, if you lived in a
condo building and your unit was on the second floor or higher, or if the
second floor of your home was concrete sub-floor. Whenever you are
installing a floor that requires underlayment on the second floor or higher,
be it in a home or a building, you will not need a moisture barrier and the
Standard Foam will be an acceptable underlayment. (Note; if you are
installing the floor in a building or home on the second floor or higher and
require more sound reduction, a Modified or Upgraded underlayment may be
required. This is discussed in another section below). If you have a plywood
sub-floor and under the plywood is a crawl space, while it might not be
required, we would recommend using an underlayment with an attached
underlayment, or laying down a 6mil plastic prior to the Standard Foam. We
will discuss the plastic moisture barrier further in the next section.
So let's recap. If you have a sub-floor that is well above grade (above the
ground, dirt, etc.), whether it is plywood or concrete, the Standard Foam
can be used. If you are installing a new floor on the second floor or higher
of your home or building, the Standard Foam can also be used providing you
do not need to reduce the sound traveling below the floor. If you need
protection against moisture, the Standard Foam cannot be used, or it can be
used in conjunction with a 6mil or thicker plastic moisture barrier. If you
are on a second floor or higher, and require above average sound reduction
(need to reduce the sound traveling below the floor), the Standard Foam will
not be the choice.
Combination Foam/Film (sometimes referred to as
"Combo" underlayment)
What is it? - Combo Underlayment is essentially the same as the Standard
Foam except it has a moisture barrier attached to the bottom. This moisture
barrier prevents moisture from getting up into the flooring and potentially
causing major damage. As with the Standard Foam underlayment, each
manufacturer may have their own specific branded name for this product, but
they do not vary much in quality. The thickness is the same as the Standard
Foam, as are the levels of sound reduction, comfort, and sub-floor
correction. Depending on the manufacturer, the size of the rolls in which
this underlayment is sold also vary. Again, if it is possible to take
advantage of the larger rolls, the benefit is usually a slightly lower
square foot price.
Where is it used? - The Combination Foam/Film underlayment is used wherever
there would be the possibility of moisture coming up from the sub-floor.
Most of the time this would be on the ground floor when you have a concrete
slab (sub-floor). As we mentioned in the last section, if you have a plywood
sub-floor that has a crawl space under it, in other words it's just above
the ground, we would recommend using this Combo underlayment as an added
precaution.
Note: While it is very rare these days, in some cases certain manufacturers
may not offer the Combo underlayment. If you need moisture protection, but
the manufacturer does not offer the Combination Foam/Film underlayment, then
you will need to lay down a 6mil thick plastic first, and then install the
Standard Foam underlayment over it. 6mil plastic is acceptable to most
manufacturers, but make sure to check with the manufacturer of the flooring
you are going to install if you have to use this method.
Modified or Upgraded Underlayments
What is it? - Modified or Upgraded underlayments refer to underlayments
which are usually thicker and/or denser than Standard Foam. These
underlayments are sometimes constructed out of a denser foam, closed cell
foam, fiber, or rubber. Their main purpose is to reduce more sound than the
Standard Foam type underlayments. These underlayments offer a higher level
of sound reduction. The level of comfort and sub-floor correction would be
the same as the Standard Foam and Combo underlayments. One misconception
with this underlayment is that it reduces the topical sound dramatically
versus the Standard Foam. If you are installing laminate flooring on a
ground floor, Modified Underlayments will only slightly reduce the topical
sound when you walk on the floor. Their main purpose is to reduce sound
traveling below the floor.
As with the other underlayments we have discussed, each manufacturer has
their own branded name for these underlayments. Unlike the other
underlayments in this article though, they will vary in thickness, type of
construction, sound reduction levels, and overall quality. As an added note,
some of these underlayments are available with a moisture barrier attached,
and some are not. Read the next section to get an idea of where these
underlayments are most beneficial.
Where is it used? - Modified or Upgraded underlayments are most commonly
used on a second floor or higher. In some condo building across the United
States, if you live on the second floor or higher, they have requirements
where if you install a laminate floor, free-floating wood floor, or ceramic
tile, you need to use an underlayment that reduces the sound traveling down
to the floor below you. These underlayments would also be used if you were
installing the flooring on the second floor of your home and felt there was
a need to reduce the sound below that level. You can use these underlayments
on the ground floor of your home, but there will not be a substantial
reduction in sound when you walk over the floor with hard heels for example.
It will only be a minor reduction. With that in mind, you will need to
evaluate your situation, and decide whether or not the added expense for
this type of underlayment is necessary. As we mentioned in the introduction
of this article, there are some dealers pushing this type of underlayment as
they do upgraded carpet padding. This type of underlayment should not be
sold as a product that will provide "increased comfort".
Note: In some cases, if you live in a condo building on the second floor or
higher, they may have rules that determine what type of underlayment needs
to be used. They may also require that you install underlayments that reduce
the sound even more than these underlayments. In these cases, usually "cork"
is an acceptable underlayment. We discuss cork in the next section. In our
experience, if you do live in a condo, we would highly suggest getting a
copy of the condo rules to see what is required. We also suggest that prior
to the commencement of any flooring work, you get a letter signed by the
condo board reflecting the type of underlayment you will be using and that
it is acceptable to them.
Solid Cork Underlayment
What is it? - Solid Cork underlayment is simply constructed out of cork. The
most commonly used cork is 1/4" thick, but the thickness may vary depending
on the vendor selling the material. The Cork is generally only used when it
is required, because the cost is much higher than other underlayments, and
it has to be glued down to the sub-floor. The cost of Cork varies, ranging
between $0.75 to $1.50 per square foot, plus the cost of the Cork
installation. The sound deadening level of Cork is very high. It does not
increase the comfort of the floor. Also, when installing cork the sub-floor
must be flat.
Where is it used? - Solid Cork underlayment is used when a high level of
sound reduction is required. As we mentioned in the previous section, we are
referring to the sound traveling below the floor, not the topical sound you
hear when you walk on the floor. Cork is most commonly used in condo
buildings where it is a requirement. Cork underlayments are usually 1/4" in
thickness. They are installed by being glued directly to the sub-floor, and
then rolled with a weighed roller. Cork underlayment can be used as an
underlayment for the installation of laminate floors, free-floating wood
floors, as well as ceramic tile.
Another use for Cork is to increase the height of the sub-floor. Here is an
example. Let's say that there is ceramic tile throughout the living areas of
your home, and carpet in the bedrooms. You decide that you want to install
laminate flooring in the entire house including the bedrooms. You are now
faced with a height difference. The difference being that when you take up
the carpet in the bedrooms, the tiled area will be higher than the bedroom
sub-floor. You can install the laminate flooring over the tile since it is
free-floating floor, but what do you do about the height difference in the
bedrooms? You can go through the huge expense and mess of ripping out the
ceramic tile, or take the easy route and install cork in the bedrooms prior
to the laminate flooring. The cork will bring the height in the bedrooms up
to the same level as the ceramic tile. This way, you can now install the
laminate flooring in the entire area without any changes in the finished
height.
Summary
Once you have read this article, you should have a good understanding of
what underlayments are and how they are used. The decision to use one
underlayment over another is, in most cases, is a personal one, unless of
course a specific underlayment is required. One thing that we have found
since we started selling free-floating type floors many years ago, is that
in some cases using a thicker underlayment can sometimes actually make the
floor sound more hollow than with the thinner types. In our opinion, this is
common sense. The farther away you get the flooring from the sub-floor, the
larger the gap or area where sound can be trapped. In plain English, the
larger the space, the more hollow the sound. This is not true though if the
underlayment is the same thickness as a standard type, but much denser.
Bottom line, figure out what underlayment is best for you and don't go
overboard. If you feel that the standard type underlayments are right for
you, they probably are. Don't loose sleep over it. There are more important
things in life to be concerned with.
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