Installing the flashing
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Slip flashing under siding
Snap a chalk line, cut out the siding and tack up
the ledger board. Then slip flashing behind the
siding, covering the top edge of the ledger.
Start by making an outline on
the siding where you want to
position the ledger board. Make
the outline large enough to include space
for the deck boards on top, the ledger and
any trim boards on the sides. Then cut
away the siding.
Nail undersill trim (J-channel will also
work) over the bottom cut, using
11-gauge aluminum nails. It's a tight fit to
drive the nails into the undersill, but you
can gently pull back the siding, then tuck
it into the undersill after you nail it. If necessary,
remove a few pieces of siding, nail
the undersill, then replace the siding.
Tack Z-flashing over the channel,
extending it slightly past the cutout on
both sides. If you need two or more pieces
of flashing, overlap the joints by 4 in. and
seal with silicone caulk. Avoid using galvanized
flashing with ACQ treated lumber
because it can cause corrosion.
Nail J-channel along both sides of the
cutout. Then tack the ledger
into place with 16d nails. Next,
slide drip flashing behind the
vinyl so the lip fits over the top
of the ledger as shown at right.
Install undersill trim along the
edge of the vinyl, over the
flashing at the top and bottom.
Then lag-screw the ledger to
the house using the fastener
pattern approved in your plan.
A building inspector we talked
to said that incorrectly installed
ledgers are the main cause of
problems in do-it-yourself
decks because the ledger may
pull loose from the house.
Make sure to get a building permit before starting a deck project so the
inspector can check the ledger installation.
It's extremely important for the ledger to
be firmly attached.
Finally, caulk around the bolt heads to
seal the holes against moisture.