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| Wrapping a column with finished material
used to be easy. Up until about ten years ago, quality redwood, cedar,
and Douglas Fir were available at reasonable prices for exterior use.
I'd just backprime the wood a little, wrap the post with building
paper, then nail on the 1x. That's the same method my father's carpenters
used, too, and they didn’t even back prime that old-growth fir.
Much of it is still holding up well today. |
I used to follow their example on
the details, too. Once the column was 'boxed out', I'd add a plinth
at the bottom, a basecap above, maybe some collar moldings, raised
panels—whatever else was called for. But these days, old-growth
cedar, redwood, and fir aren’t available at any price, and
second growth lumber just doesn’t last as long, even if you
prime it.
Thanks to technological improvements in adhesives
and milling, there are a variety of alternative materials available
today for exterior trim. Like many carpenters and contractors, I've
discovered that new technology has changed my job. Reading and research
are now just as important as joinery. |
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Include a Drain Plane |
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For the post wrap in this article,
I used Windsor
One boards—fingerjoint exterior-grade material with two
coats of a highly durable primer. The manufacturer’s instructions
are clear and simple: Prime all cut edges. For some exterior trim
materials, special fastening techniques are also required. Be sure
to read the instructions that accompany the trim product you're
installing.
But no matter what product I install, I no longer
'sandwich' exterior trim like I used to. Rather than adding plinth,
collar moldings, and paneling on top of boards--which invites rot
and mold, I now spend a little more time and effort maintaining
a clear drain-plane path, so water or moisture won't be trapped
inside the column or between boards, and I allow plenty of room
for air circulation, so mold and rot won't develop. Remember, caulking
is a last layer of defense, and it's not always required. |
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| Wrap the base of the post with a self-healing
waterproof membrane (Fortiflash
by Fortifiber). |
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Avoid a big mess and peel the backing paper off
as you go. |
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| If the hardware or bolts are in the
way, bore holes or mortise the back of the plinth pieces as necessary. |
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But be sure to prime any holes or cuts, especially
if you wonn't be able to reach those areas after the material is installed.
Keeping primer nearby is a must when it comes to installing exterior
trim. |
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| I use a plastic yogurt container with
a slit cut in the top so the paintbrush fits through. That way
the brush won't dry out, and the lid stops the paint from getting
all over my hand. |
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For raw edges that form joints, use glue to seal
the wood, rather than paint. Apply the glue liberally, spreading it
evenly and completely across the raw wood.. |
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| Only after ever piece has been sealed,
and all the joints glued, is it safe to fasten the pieces together,
first with 2 in. galvanized brads, and then with trim-head screws
(more on trim-head screws later). |
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| Backing nailers must be installed before the plinth,
but be sure the backing doesn't extend above the plinth |
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| After priming the backing, nail it to
the post permanently. |
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| Then slip the plinth over the post... |
...and glue up the last piece. Use clamps
to draw the joints tightly closed before nailing the corners. |
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| Shim the plinth up off the concrete pier slightly,
so that it will be just above the finished patio surface; whether
the finished surface is brick, concrete, stone, or a wood deck, always
allow room for moisure to drain and air to circulate beneath a column. |
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Tack the plinth in place; be sure it's perfectly
level and plumb before fastening it to the nailers |
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Use A Brake |
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If you don't have a brake to bend
metal flashing, make one from two pieces of 1x12 or scraps of heavy
molding and a piano hinge. With a brake, you can make any size flashing
you need, rather than fighting with store-bought flashings that
are never the right size. |
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| First make the bend for the drip edge. Layout
lines help keep the material square and ensure a perfect bend on every
piece. |
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Clamp a third piece of 1x on top of the metal, to
hold it securely while bending. |
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| Notice the back of the third piece clamped
on top of the flashing is ripped at a bevel--about 3 degrees, so the
bend will be a little greater than 90 degrees. |
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To make the second bend, place the piece under the
clamping fixture (use a layout line to keep it square), then slip
another piece of flashing under the drip-edge bend, so it won't hang
up while lifting the face of the brake. |
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Install The Flashing |
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| For the first piece of flashing, mark boths sides
of the post on the nailing fin. |
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| Cut the shoulders on the nailing fin, |
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| ...then trim the tabs off so they're
about 1 in. long and... |
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...bend the tabs down onto the top of the plinth. |
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Mark the second piece of flashing at
the base of
the
nailing fin... |
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and this time cut just beneath the nailing fin. |
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| Bend the nailing-fin flaps around the
post, |
then remove the flashing and crease the corners
flat. |
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| Install the flush-cut flashing first, and apply
waterproof polyurethane-based caulking in the corners. Be sure to
use a sealeant that's compatible with the flashing system. Some caulking
sealants include plasicizers that are incompatible with rubberized
asphalt self-adhering flashings and with paper/asphalt/paper laminated
flashings. To be safe, use the proprietary sealant manufactured
by the flashing company (Moistop
Sealant by Fortifiber). |
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| Next install the overlapping flashing.
Tack the flashing to the post with compatible nails (aluminum nails
for aluminum flashing; galvanized nails for galvanized flashing). |
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| For extra protection, and especially when I'm installing
a basecap on top of the plinth, I always install an additional layer
of seal-healing peel & stick flashing on top of the metal flashing--just
in case a few nails penetrate the metal. |
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Waterproof Wrapping |
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| Building paper, like Jumbo Tex, is fine for wrapping
posts, but I prefer using Moistop because it's more durable and isn't so easy to tear during installation. |
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| Moistop is availabe in 18 in. rolls,
so a single length can wrap a 4x4 post. But if you must make
a vertical seam, be sure to overlap it by at least 6 in. Otherwise,
start wrapping the post at the bottom and work your way up, so the
horizontal seams cover each other, shingle-style. |
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| Using a rainscreen, is the best way to build long-lasting
columns. Home Slicker's three-dimensional nylon matrix allows moisture
to travel easily down and out of the column (Home
Slicker by Benjamin Obdyke). A good rainscreen also provides a
pressure equalization area between the siding (or trim) and the framing,
which allows air to circulate freely so moisture can dry out naturally. |
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| Rainscreen will not only help prevent
mold and rot, but with proper drainage and circulation behind the
trim and siding, paint will last much longer. Installing
Home Slicker is easier than housewrap because it doesn't have to be
water tight. Just be sure the ribs are running vertically, so
that moisture and water will travel down the post. |
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| Once the rainscreen is installed, I make up a three-sided
base-cap collar. The material is ripped from 1 1/8 in. net Windsor
One stock, with a bevel on the leading edge. |
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| Though the manufacturer prefers
butt-jointted corners, this molding has to be mitered. After
applying an excessive amount of glue, I use Collins
Spring Clamps to secure the miters... |
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| ...then shoot 18ga brads to lock the joints together
while the glue dries. |
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Shim the basecap off the plinth about 1/8 in. before
fastening the basecap to the post, so that moisture can drain from
behind the trim. With an extra layer of Fortifiber on top of the flashing,
I don't have to worry about the nails penetrating the metal flashing. |
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| I always pre-assemble as many parts as possible
before applying them to the post. In this case, I glued and
nailed together three sides of the post-wrap... |
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| ...then slid the assembly over the post
and installed the last piece using clamps to hold the joints tight. |
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| Once all the pieces are on the post, I install trim-head
screws through every joint--about 12 in. on center up the post, in
the joints on the plinth, and through the basecap miters, too. |
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| Always drill pilot holes for screws
that are close to the edge. These trim-head screws are self-taping,
so in the field it's safe to go without a pilot hole. Most trim-head
screws require an 1/8 in. pilot hole. For driving screws I use
an impact driver, and counter sink them about 1/8 in. |
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| Nothing looks worse than a framing nail in finish
work. Trim-head screws are the perfect alternative. They leave a larger
hole than a finish nail, but much smaller than a regular screw.
The best screws for exterior use are square-drive and stainless steel
(Mc
Feeley's Sqaure Drive Screws). |
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| Once the column is wrapped,
it's time to turn to the beams...but I'll leave that for a future
article, along with additional ideas for decorating Colonial, Victorian,
Arts & Crafts, and contemporary columns. |
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