Heritage Restoration, Inc.

Trouble With Finishes Is That They Fail

The trouble with finishes is that they fail.  How long until they fail depends on many factors some in your control, some not so much.  Modern finishes make your selection even more complicated, with such descriptions as “Waterborne Oil-Modified Urethane Dispersions for High-Performance Interior and Exterior Wood Finishes, but as always, price and quality dictate how good they are.


Interior Wood

Interior natural finishes all depend on they appearance you are shooting for, and how the finish will be used.  Natural interior wood finishes run all over the place, from traditional shellacs, lacquers, waxes, oils like Tung or linseed, each with their own advantage, application technique and wear.  Synthetics like polyurethanes are all over the place, so ask a professional.


Floors need the most protection.  The trouble with floor finishes for me is a lack of maintenance and inability to recoat them without sanding thorough to the bare floor.  When you sand a floor 5-6 times and it is all done.  Nothing is worse than losing a perfectly good floor to too much sanding.  Use a finish that wears well and can be recoated.  I like the polymerized Tung oil finish.  Polymerized Tung oil finishes are hard yet flexible, waterproof and impervious to alcohol and many food acids, so they are good for almost any surface.  And they can be recoated.  I have used with success good oil based polyurethanes, but the have failed me too often.


Exterior Wood

Wood wants to decay.  Exterior natural wood finishes are subject to much harsher conditions, where the selection of the finish will have a profound effect on performance, longevity and beauty.  The goal is to reduce the decay to a manageable or preferred life cycle.  If you are building a deck and you expect the frame to last for 10 years, do nothing to the decking.  Or if you build a frame to last a century, build the frame right, flash it right, and take care of the deck that covers it.



Cleaning the wood is essential for finishes absorb and protect.  There are a number of deck cleaners to remove lichen and mildew.  It can be either hand applied and scrubbed, or cleaned using a pressure washer.  Pressure washers must always be used with care.  The type of spray tip controls the strength and width of the spray; too hard and a concentrated spray will forever damage the wood and look like a zigzag pattern.  Use a pressure washer light and even, enough to remove the build up but not scar or fur the wood.  If the wood does fur up, you will have to sand it before applying a finish.  Start soft and work your way up.  Do not be impatient. The idea of a pressure washer is to use very little water.  Once the surface is clean, allow it to dry for several warm days, or wait till the next weekend.


To Seal or Preserve

Outdoor clear finishes take maintenance; there is no way around it.  Anyone with a boat knows that.  Good finishes like a varnish (natural resins) or a polyurethane (synthetic resins) can be successfully used for doors and other vertical surfaces, although decks and horizontal surfaces are different.  I choose a preservative over a sealer, since sealing does not treat the wood it just puts on a protective barrier that wears off.  Preservatives protect exterior woods from premature losses of color, rot, surface mildew, and water absorption.  Hardwoods and softwoods require different types of preservatives.  And everything has specific recoating cycles, with some finishes requiring an application every year for two years, then every five years.  New woods should season for about a year before coating.  I use a Brazilian nut oil preservative for harder woods like mahogany and ípe.  For woods like pine and cedar, I use an oil wood preservative designed to penetrate soft woods.  It is never too late to apply a preservative.



Paint is a fine choice, although the kind of paint and your prep is essential to a long lasting deck finish.  I would paint a covered porch before I would paint a fully exposed deck.  I still used oil based decking paints, but if you use a latex based, apply three coats for extra protection.  Paint works well to protect a wood from organic build up, as well as prevents woods for drying and cracking, which later leads to failure.


The next column will focus on the construction, care, and safety of decks.  Feel free to ask any questions you have about the care and maintenance of you building.  There is nothing off the table.


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