By Bruce W.
While remodeling and repainting an old garage, I found one small spot where
the redwood siding had some rot damage. Luckily the decay was shallow, just over
half of the way through the 3/4" thick board.
One repair option was to cut away a section of the siding long enough to span
between adjacent studs, and replaced it with a short piece of new siding. While
I did have some new siding that was a close match, I decided to try to graft a
piece of treated pine onto the damaged area.
|The section of rot damage.
I had already power-scraped the paint from the siding and given it a
coating of primer.
I could have filled the entire void with some sort of filler compound,
but my experience is that neither epoxy nor polyester fillers work well for
large and deep voids. The stuff will droop out of place before it
hardens, or I won't be able to get a uniform thickness and I'll have to apply a
second coating, plus there can be lots of time spent sanding down the lumps to
make the patch look flat like wood.
Even if I managed to get a good-looking patch from filler compound, there's a
good chance that it will fall off someday.
||I poked at the wood to make sure the rot didn't go all the
Even if the rot did go all the way through, I could still make a patch,
but my approach would be different.
|I used a cat's claw to remove the nails from the
||To prevent the heel of the cat's claw from making a dent in
the wood, I placed a putty knife beneath it.
I laid out the 3 sides of the patch with a pencil and a speed-square.
|I made a series of shallow cuts with a circular saw. I used
a cordless saw with a 5½" blade, but a regular circular would have
worked just fine.
I like this tool because it doesn't kick out as much dust as full-sized
saws. I can get my face closer to see what's happening.
||My initial thought was to make just one cut to define the
upper edge of the graft, but then I realized that I could make a series of
parallel cuts that would weaken the wood I wanted to carve out.
|I used a sharp 1 inch wide chisel to slice away the thin
strips of wood that remained.
||Usually I would be able to hammer the chisel this way to cut
across the grain, but this old redwood was really hard.
I noticed the hardness of the siding before I started working on the
garage, and it led me to believe the siding was Douglas Fir. Only after
power-scraping an entire painted wall did I realize that this was redwood.
The near-complete absence of knots was one major symptom, besides the red
|I used one of my secret weapons: The
Poor Man's Roto-Zip. This is a Dremel Moto-Tool with an accessory base
plate that enables the tool to make cuts of a precise depth.
The adjustable base plate (Sears Craftsman, about $20 including two
cutting bits) just screws onto the end of the rotary tool, after the nose
piece is unscrewed.
These tools accept 1/8" diameter cutting bits, which is the
standard size Roto-Zip bit.
||I set the cutting depth and made vertical cuts along both
|I used a chisel to clean out the bottom of the
My cuts were about ½" deep, so they went two-thirds of the way
through this siding, which is 3/4" thick.
||The completed cut. I don't know if this qualifies as a "mortise".
Since this is tongue and groove siding, the tongue of the board below
My patch will need special preparation to handle this.
Note: Since writing this article, I have purchased a Fein
Multi-Master, which is similar to those inexpensive detail sanders, but it also
has scraper blades and (the most useful) a fine-toothed saw blade. Since the
blade rotates back-and-forth only a fraction of a degree, it can make a
square-sided plunge cut and quickly accomplish what I did above with a moto-tool
and a chisel. At $200 plus, it's not cheap (hey, it's made in Germany) but it's
worth the money just for the saw feature.
Cutting The Patch:
Using a circular saw I ripped a piece of treated pine 5/4 x 6 deck board to
the desired width. I had brought a miter saw along, but not my table saw. I cut
the board a couple of inches longer than needed, just in case something went
wrong during the tricky part.
Splitting The Board Down The Middle:
I placed the board on edge on the miter saw. This is a risky cut
to make, and I'm sure that the saw manufacturers would "have a
cow" if they knew I did this.
Since the fence has a gap adjacent to the blade, I used a small block
against the fence (red arrow) to keep the strip from moving around.
I cut the piece very s-l-o-w-l-y and held on tight. I cut one end and
then flipped the board around to cut the other end.
||But the cuts did not meet in the middle, so I finished the
cut with the circular saw. A hand saw would work just as well for this
In fact a hand saw would work just as well for the entire cut, but it would
take a while. If I had planned my project better I would have made this cut at
home on the table saw, or I could have purchased a ½" thick piece of
hardwood at Home Depot.
|The filler piece after being cut to the desired thickness.
||Remember that I mentioned the tongue from the siding below?
Using a circular saw with a ripping guide (red arrow) I made a couple
of cuts to form a rabbet (rectangular notch) in the back edge of
|The profile of the rabbeted filler piece.
Again, this would have been easier to cut on a table saw. I think I
need to buy a small table saw to keep in my truck. Hmmm...
||After I had cut the board to width, I used the miter saw to
cut the board to length. I often start with an extra-long board, just in
case I muck up one end or something.
I tested the board to see how well it fit the hole.
|I pre-drilled a hole at each end, and drove in a 2"
deck screw, just to make sure the filler board would lay right without
rocking too much.
It might have been better to drill two holes at each end, which would
have given me better control in making the piece lay straight. Luckily I
didn't have any problems.
||I applied a hearty dab of urethane glue. It's
important to use outdoor-rated glue for something like this.
Ordinary carpenter's glue will hold fine... until the first time the wood
gets wet or really damp.
|I installed the filler board, drove in the screws, and let
the glue dry.
This urethane glue takes 4 hours to cure. It oozes foam while it
hardens, which helps to fill the gaps.
Once the glue was dry I sanded the area with a belt sander.
||I applied some fast-setting polyester filler to the
small voids around the filler.
essentially "Bondo" auto body filler, though it's marketed as a
wood filler. It hardens in about 10 minutes and doesn't shrink.
I've also used WoodEpox from Abatron, but it takes a lot longer to
|I covered the bare spot with oil-based primer.
||The next day I "painted" the wall with oil-based solid-tone
stain. It's actually a tan color, though it doesn't show up very dark
It's impossible to see the patch unless you get really close.
|This is the garage after all the trim was replaced and
the painting was completed
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- Treated Deck Board, Scrap
- Urethane Glue
- Deck Screws