Heritage Restoration, Inc.

Repairing Exterior Wood

All exterior wood fails eventually. If the wood is historic or a ten-year’s-old, the options are the same, but the choices affect longevity, performance and your wallet.  So before you slap on some wood putty, consider the options. There are many ways to repair wood; some quick fixes, some more permanent.


Quality versus Junk

Wood is a persnickety thing.  The specie of wood, where it was came from inside the tree, the grain direction, how it was grown or how it was milled all effect longevity.  My rule of thumb is if it still exists, then it is good.  Consider a 150-year-old piece of cedar versus new.   The old piece took it time to grow, maybe several hundred years.  The grain is nice and tight, maybe 20 rings per inch (each ring is one year).  Then take a new piece of cedar where the tree’s growth is accelerated and the growth rings are about 2-4 per inch.  More space, lower quality.


Knots are bad.  A knot is where a branch came out.  The grain around the knot absorbs moisture and fails prematurely.  You want straight grain, it is more likely to stay straight and last longer.


The US Forest Service has a chart grading the comparative decay of heartwood, from very resistant to nonresistant woods.  The best native wood from a local lumberyard: Cedar.  The worst: Pine. www.fpl.fs.fed.us/documnts/fplrn/fplrn153.pdf. 


Pressure treated is OK for about 15 years, until the chemicals wear out and then you are left with junk pine.  Finger jointed can be OK, it just depends on the glue the manufacturer uses.   And fake wood is fake wood.  It fails too, it just will never rot.


Identify Failure

Understanding why wood failed is the first priority.  Wood essentially fails, or rots like it should, from sun and moisture.  The type of rot is less relevant then why it rotted. Water is typically the culprit for rot, so identify where and why the water got in.  Typically poor caulking is a wood killer, trapping moisture in end grain, and making even the most resistant wood to rot.


Dutchman Repair

A dutchman repair is where you carefully cut out a piece of wood and replace it with a well-fitted, in-kind piece of wood.  In kind can the same density, like soft with soft and hard with hard, or pine with pine, cedar with cedar.  The well -fitted dutchman can be either dry fitted and fastened with a screw or nail, or can be glued or epoxied.


Wood Filler

Wood filler is for holes, not for replacing wood.  Keep wood filler under a dime in size.  It gets really hard and eventually falls out, or traps more moisture and causes more rot.



Epoxy is a good option when full replacement or a dutchman is not used. Epoxy is a thermosetting polymer formed from a reaction of a resin with a hardener.  Do not confuse it with other two part systems used for cars; it is not the same thing.  The goal is to bond the wood with the epoxy.  The best method is to remove any rotted wood and leave a rough surface.  Sometimes drilling holes to “key” the epoxy is necessary.  Apply the liquid epoxy to the rough surface, and then put epoxy with the consistency of putty on top.  Sand smooth.


Full Wood Replacement

When too much of the wood is rotted, resort to replacement.  Find or cut new wood that is the same density, rot resistant and the same thickness and width.  A lumber supply may be the best choice.  Back prime, especially edge grain, all exterior wood before installing.  If you need to cut a joint, cut it on an angle where the longest part is facing out, this allows water to naturally shed.  Use shims to get the right plane, dry fit, then screw or nail the repair on.


Remember, good materials and technique always make the effort last longer.  Spend the money on good material; it is the cheapest part of a good repair.  Use sharp tools. Read directions.  And as always, be safe.



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