the
washington
post
.
thursday,
june
9
,2022
DC
2
HomeEditor:
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ON THE COVER
Anne Bentley/Illustration for The
Washington PostLOCAL LIVING
One problem in your case is the
way the siding meets the base of
the shed. Siding on sheds usually
sticks out more than the
foundation or floor, which allows
rain to run down the siding and
onto the ground. It’s similar to
what campers have learned about
tents and the tarps underneath: If
the tarp is not completely covered
by the tent, it will collect water.
Your shed, though, has a base
that e xtends past the wall. It
appears that there is flashing at thebase, with one long edge of metal
extending up behind the siding,
and another wrapped around the
base of the shed. This keeps water
out of the shed’s interior. If
installed correctly, it could also
help protect the siding. But the
bend between the wall and the
base must be more than 90
degrees, sloping away so water
drains at the base of the siding.
This kind of flashing usually comes
with a suitable bend, but installers
who don’t understand the nuancesBY JEANNE HUBER
Q: I have a shed with fiber cement
siding that is disintegrating a few
inches around the bottom. T he
rest is in good shape. We
previously replaced half a panel,
using bent metal channel and
caulk, then painted it over. We
also tried a PVC board along the
bottom, bent metal channel and
caulk. Is this the best alternative?
A different contractor wanted to
attach PVC on the outside of the
siding. Wouldn’t this collect water
and rot out above?
South ArlingtonA: From the close-up picture you
sent, it’s clear that the siding on
your shed is not fiber cement, but
OSB, or oriented s trand board. It’s
made of thin flakes of wood
layered and glued together,
topped by a thin laminate
textured to resemble T1-11
plywood, which resembles rough-
cut boards aligned vertically, side
by side. The T1-11 look is also
available in fiber cement panels,
which are made from Portland
cement, sand, water and cellulose
fibers (wood pulp). But the
crumbling wood fragments at the
base of your shed’s wall leave no
doubt about what material you
have.
OSB siding is relatively s trong.
It comes pre-primed, which saves
time when building. And, unlike
fiber cement panels, it can be cut
with the same tools you’d use for
wood. T hese features, as well as
the cost, make OSB siding a
bestseller for siding on garden
sheds.
At the L owe’s in Alexandria, LP
SmartSide OSB siding in the T1-11
style is $40.83 for a 4 -by-8-foot
sheet about^1 / 3 of an inch thick.
Plywood in a similar look costs
pennies less ($39.72), and it’s
thicker, a little over 1 / 2 inch. But it’s
sold without a finish, because
people can opt to stain rather
than paint it. Fiber cement siding
is more expensive, at $57.38 for a
sheet of HardiePanel Sierra 8.
OSB and fiber cement siding
come pre-primed, because they
must be painted; staining is an
option only with plywood siding,
because it has a layer of wood to
stain. All three materials swell
when they become damp.
Plywood generally shrinks back
into shape once it dries, provided
the adhesive between the layers is
rated for e xterior use.
Manufacturers treat OSB and
fiber cement products to resist
moisture, but the protection isn’t
perfect. And if the products do
absorb moisture, they will swell
and become permanently
distorted.of the angle can force the metal
into a right angle — or less than
one — when they nail it on.
What can you do? If you can
find matching siding, it might be
possible to cut off the lower
portion of the damaged siding
using a circular saw — or hire
someone to do it for you. C heck
for nails before you decide where
to cut, and nail a s traight board
below where you will run the saw
to use as a guide. Set the blade
depth to the thickness of the
siding or a little less; you can
clean up the back of the cut edge
with a utility knife. Once the old
wood is out, check the angle of the
flashing. If it is not draining water
away from the shed, replace it,
nailing it to the wall in a way that
keeps an angle along the base that
will shed water.
Before you cut the replacement
siding, factor in allowances for
the top and bottom edges. At the
top, between the new piece and
the old siding, you will need Z
flashing, which tucks behind the
upper piece and covers the top
edge of the new piece. In sizing
the replacement, allow for a gap
of^1 / 4 inch between the top siding
and the part of the Z flashing that
extends below it. Also allow for a
gap at the bottom edge of the
replacement. Although 1 / 4 inch
might be enough here, too, a
wider gap, say^3 / 8 , will be easier to
keep clean of debris.
Siding is usually installed from
the ground up, so when there is a
horizontal seam, such as in eave
ends of sheds, the Z flashing
between sheets is set on the top
edge of the bottom piece over a
bead of caulk, then held in place
with the wide heads of roofing
nails driven into sheathing, with
no nails through the flashing.
If you’re doing a patch job,
you’ll need to set the flashing on
the top edge of the replacement
piece and wiggle the top of the
metal up and under the lower
edge of the original siding. Prime
the cut edges, and be sure to leave
that^1 / 4 -inch gap, so the lower edge
of the original siding can dry.
If you can’t find matching
siding to use as a replacement
around the bottom of your shed,
PVC board could also work,
assuming you can find material
that’s as thick as the siding.
Install Z flashing between the
board and the siding above, and
leave a^1 / 4 -inch gap. PVC won’t
absorb moisture, so a gap at the
bottom is probably not critical. Have a problem in your home?
Send questions to
[email protected]. Put “How
To” in the subject line, tell us where
you live and try to include a photo.HOW TO
When replacing siding, pay attention to flashing
READER PHOTOS
A reader wants to know how to fix this shed siding. If you can
find matching siding, it might be possible to cut off the lower
portion using a circular saw — or hire someone to do so.