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Q: polyurethane sealer ( Answered,   0 Comments )
Subject: polyurethane sealer
Category: Family and Home
Asked by: jodi65-ga
List Price: $10.00
Posted: 01 May 2006 13:09 PDT
Expires: 31 May 2006 13:09 PDT
Question ID: 724461
why is polyurethane sealer recently applied to redwood deck bubbling
and peeling? And how can I rectify this and apply additional coats?
Subject: Re: polyurethane sealer
Answered By: crabcakes-ga on 02 May 2006 10:27 PDT
Hello Jodi65,

 Was your deck completely dry before applying the sealer? If your
sealer is oil based, and it was applied over an existing water based
product, this problem can occur, as moisture in the wood has no place
to evaporate ? causing bubbles and peeling. It sounds as if it?s
sealer removal time for you! There are some methods to stripping a
deck below in my answer.

?Paint peeling, blistering and flaking occurs when moisture under a
non-breathing film finish destroys the film's adhesion to the wood. A
properly installed vapor barrier is the recommended way to control
this problem. Vapor barriers should be on the warm side of the wall.
Problems also may be caused by faulty surface preparation, or the use
of incompatible materials.?

   ?Varnishes and polyurethanes crack and peel when used for
exteriors. They are difficult and expensive to apply and deteriorate
quickly. Removal is expensive and difficult.?

?  Apply finishes on windless days. Temperature should be between 50
and 70 degrees Fahrenheit.
?  Surfaces should be clean and dry. 
?  New structures built with unseasoned wood should air-dry one month
before finishing.
?  Back-priming is recommended for all exterior finishes, particularly paints.

?  Don't mix incompatible materials. Finish failures may result from
mixing incompatible products or applying them over one another.
?  Moisture is the most common cause of finish failures, so use proper
vapor barriers, air vents and flashing in new construction.

Please see the web site for further information. Because of copyright
restrictions, I can not post more from this site, but scroll down to
?Removing Finishes? to find how to remove your sealer.

   ?Redwood takes and holds finishes better than most other woods. For
long lasting good looks and performance, a quality water repellent
finish containing a mildewcide and an ultraviolet inhibitor is
recommended For best results, the finish should be applied directly to
the lumber before construction covering all sides, edges and ends. A
second application is recommended when the deck is completed.?

   ?It is not a good idea to paint a wood deck. Instead, use a
penetrating stain or a latex stain, followed by polyurethane sealer.
Experts recommend against using paint on wood deck boards for two
reasons: 1) the unpainted underside of painted wood deck boards
absorbs moisture, which can result in peeling paint on the surface of
the boards; and 2) a painted deck gets hot enough to make walking
barefoot painful, especially for tender baby feet.

            Many fine stains are available. If you are planning to
finish the deck yourself, ask your contractor, builder or lumber
supplier for advice. If you used concealed deck fasteners, you won?t
have to worry about removing any splinters, because, of course, there
won?t be any. However, if you used nails or screws, you may need to
lightly sand splinters or rough areas.
            Before staining, carefully sweep your deck, but don?t hose
it down. You can remove pencil marks made during installation with a
little rubbing alcohol. And before applying polyurethane sealer,
follow the manufacturer?s instructions, and wait for a spell of dry

1.	Follow manufacturers label instructions (they have been tested).
2.	Don't mix materials / or apply over another finish.
3.	Unseasoned wood should dry 30 days before finishing (except K.D.)
4.	Use exterior finish only.
5.	Always start with a clean surface.
6.	Keep sprinkler over spray off wood decking / fencing etc.
7.	Keep potted plants on coasters or mats.
8.	Varnishes and polyurethanes will crack and peel.
9.	High oils and resins attract dirt, are susceptible to mildew and darken wood.
10.	Periodic rinsing (every 60 days) will remove dirt and grime, help
preserve finish.
11.	"Clear" finishes generally deteriorate quickly.
12.	Paint your deck as a last resort.
13.	Ask a professional for advice.
14.	Always do a test area.
15.	Establish a regular maintenance schedule for your wood.

?Q. What can be done to wood if it becomes discolored?
A. A wood conditioner can be applied, followed by pressure washing,
which will remove any old coatings and prepare the surface for
refinishing. After the wood is dry, any repairs or sanding can be
completed. Most deterioration can be reversed with the right wood
cleaners and surface preparation.
Q. After cleaning, which sealer should you use?
A. If left untreated, the wood will continue to age after cleaning. An
oil base, naturally pigmented, penetrating finish will work best for a
natural wood took. The grain of the wood will still show through the
tint. and it will be protected from the rain and sun. All purpose
sealers or heavily pigmented coatings generally don't look good or
hold up well.
Experience in diagnosis of problems, execution of proper procedures
and selection of quality finishes is essential for a quality project.
For more information or to receive a free tip sheet on exterior wood,
you can call San Diego Power Wash, (619)463-2586.?

Loads of great information here:,17071,219491,00.html
and here:

and here:

?Q: I was all set to use Thompson's on my deck but after reading some
stories of other peoples experiences I'm not sure I want to use it
now. What do you suggest?
A: We do not recommend Thompson's water sealer. We suggest high
quality sealers like our ADMTM 2000. Check out

Q: My deck is six months old, pressure treated wood. I cleaned with
water and allowed to dry for a few days, then applied sealer (with a
sprayer).  I mopped off what appeared not to be taking. Waited 48
hours and applied a second coat. Again, I sponged what appeared not to
be taking. Now after 48+ hours that deck is still tacky. I am in Texas
and the weather is in the high 90's with 70+ humidity. What do I do? I
guess I screwed up by using Thompson's. Help.

A: Way over application - it's going to be sticky for a while.  It
would help to know which Thompson's product was used. Some of their
products will wear out in six months and by next year there should be
nothing left. In which case time will help you. I really need to know
more information on products used to serve you better. The least you
should do is let it wear off and maybe lightly powerwash it on evenly
using a deck stripper.?

?Q: I have tried two different kinds of deck cleaners, also bleach,
and powerwashing the deck. I have pressure treated wood and I am
trying to remove the old stain. I am going crazy, how do I get the old
stain off?

A: Try Wolman's Deck Stripper with a good pressure washer (3000psi @ 4
gallons per minute with a 25 degree tip).

Q: I want to clean my deck to restore the color. Should I use bleach? 

A: It is okay to clean the dirt off your deck, just use a good
detergent. Bleach is bleach and that will not restoring the color of
the wood it is bleaching it.  Bleach should only be used diluted and
used only to kill mold & mildew.
Scroll down to Stripping Decks

   ?Sanding is an effective method of removing old finish. However,
sanding can damage the surface of the wood. Paint strippers are heavy
duty products designed to chemically remove unwanted coats of paint or
stain from wood surfaces. They are effective but need to be used
properly -- with drop cloths and protective clothing -- because they
might contain hazardous ingredients.
A commercial cleaner, such as Wolman?s DeckStrip Stain & Finish
Remover, is easier to use than most paint and varnish strippers. It is
designed specifically for wood surfaces such as your deck. It is a
ready-to-use exterior wood stripper that removes solid and
semi-transparent stains and clear finishes -- either oil-based or
latex coatings. Other stripping products are often designed for one or
the other. It is also easy to use on vertical surfaces. It is
biodegradable and relatively safe around grass and plants, requiring
only that the surrounding area be hosed down before and after use.

Care should be taken to thoroughly rinse all cleaner/restorer products
from wood surfaces. Failure to remove dirt, mildew and cleaning agents
is an open invitation for early failure of future coatings.
Once the wood surface has been cleaned -- this would apply to all
vertical components as well as the deck flooring, railings, spindles,
vertical planks, risers on staircases, etc. -- the wood should be
allowed to dry thoroughly prior to application of a wood

Good luck with your deck! Please ask for an Answer Clarification, and
allow me to respond, before you rate, if any part of this answer is
Regards, Crabcakes

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