Bruce W. Maki,
Wood damage caused by rot is a common problem with old houses.
There are 3 requirements for wood decay fungi to flourish:
- The moisture content of the wood needs to be above 29%,
- The wood needs to be exposed to oxygen,
- The temperature needs to be above 40 degrees Fahrenheit.
The fungi that cause wood to rot are everywhere, and all they
need are a moist warm place to do their dirty work. If wood gets wet
but dries quickly, the fungi will not have a chance to grow and feed
on the wood fibers. Thus, any design that prevents water from
puddling on wood, or allows for maximum air flow around the wood,
will last longer.
||This century-old porch post had some minor rot
damage, mostly around the nail holes First we sanded the area,
then we used a flat screwdriver to pick out the soft and wet
chunks of wood.
|We applied an epoxy product called LiquidWood
from Abatron. LiquidWood is
a thin, runny material that goes on with a paint brush and soaks
into the damaged wood fibers. The wood needs to be dry and free
of flaking and crumbling loose rot, but less severely
rotted wood can remain. The epoxy will saturate the softer areas
and harden them
||LiquidWood is a two-part epoxy resin. Equal
volumes are mixed together and applied like paint.
One drawback to LiquidWood is it's long curing time. Abatron's
instruction say that LiquidWood will harden overnight, but our
experience is that it takes much longer to fully cure. We let this
post sit for a week, in summer weather with temperatures in
the 70's every day, before it was fully dry to the touch. Granted,
it felt only slightly tacky during that time. I believe LiquidWood
can be covered over before it is fully cured, because I have made
many repairs that way.
Heat expedites the curing process, and on other jobs I have used
a heat gun or a hair dryer to help LiquidWood harden faster.
|When the LiquidWood was dry, we applied a layer
of Abatron's WoodEpox, which is an epoxy dough-like filler
material. One way to apply WoodEpox is with a putty knife.
||Another way to apply WoodEpox is by hand. Rubber
gloves should be worn when handling this product.
At 70 degrees or higher, WoodEpox seems to take several hours to
fully harden. At cooler temperatures the material may take a few
days to harden. One way to check for adequate hardness is to scratch
the epoxy with a fingernail. If the scratch shows up as a lighter
color, the epoxy has hardened.
After the WoodEpox was hard we used a rasp (such as Stanley's
Surform tool) to shave down the excess material. Sometimes there are
still voids after shaving down the excess, so more WoodEpox may need
to be applied. We often fill small voids with caulk.
When the surface was satisfactory we applied a coat of oil-based
primer, followed by a coat of exterior latex satin-gloss paint.
|Update - 5 Years Later:
This repair is
still holding up perfectly. I have seen other patching materials
(like Bondo) separate from the wood, but Abatron's wood filler
has stayed put.
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- Basic Carpentry Tools
- Putty Knife
- Sanding Tools
- 2-Part Epoxy Wood Hardener
- 2-Part Epoxy Wood Filler