If you’ve been putting up with a drafty patio
door that sticks, fogs up or leaks during a
heavy rainstorm, it’s time to consider a new,
energy-efficient replacement. While a high-quality
door isn’t cheap, it’ll cut down on
drafts, require almost no maintenance, and
glide smoothly and latch securely. Best of all,
you’ll save $300-plus if you install it yourself.
At first glance, replacing such a big door may
seem intimidating. But if you read through
this article, you’ll see that it’s similar to replacing
a window. We’ll walk you through each
step, including a special section on the critical
flashing details that make the new door
leakproof.
Manufacturers of higher-quality units have
made installation fairly simple and straightforward.
If you have experience installing a
window or a swinging door, you should have
no trouble with a sliding patio door.
Other than basic carpentry tools,
you’ll only need a 4-ft. level
and a screw gun. But we also
recommend using a reciprocating
saw fitted with an
8-in. bimetal blade to
hack through shims and
nails (Photo 5). Unless
you’re a brawny DIYer,
another useful tool is a strong
helper for short periods to
assist with the heavy, awkward
panels and door frames.
In most cases, you can replace that old
slider with a smoothly operating, energy-efficient
door in about a day. Add a few more
hours to retrim the outside and the inside and
you’re done.
Measure the opening
before you buy
Before you run off to buy your slider,
pull off the interior trim around the old
door and measure the “rough opening”
for width and height. (If you want to reuse
the old trim on the new door, pull
the nails through the unfinished side.)
Make sure you measure to the framing
right next to the old doorjamb. You may
have to cut away overhanging drywall to
get at it (Photo 1). To check the height,
make sure you’re measuring to the subfloor,
that is, the wood or concrete that the
doorsill actually rests on and not a secondary
layer of particleboard or plywood
(underlayment).You can check for underlayment
by pulling off a nearby heat register
and looking at the floor layers bordering
the opening. Then select a door that
fits your rough opening. The door catalog
will list its rough opening requirements.
The door dealer will walk you through sizing
and door options. (See “Buying a Patio
Door,” below.)
Once you get your door home, you’ll
save a lot of time if you finish any exposed
wood surfaces on the door before beginning
the installation. That’ll save you from
tricky brushwork cutting in around exterior
claddings, weatherstripping and
hardware, and keep smelly finishes out of
your living quarters.
In our demonstration, we’re removing a
6-ft. slider surrounded by wood trim and
vinyl siding. Our new door was slightly
smaller so we had to deal with a small gap
surrounding the new exterior trim. Most
new replacement doors will have a similar
gap, no matter what exterior siding you
have. If your old door has exterior trim
fastened to the door frame, remove the
trim and follow the installation steps we
show. But if the siding comes right up to
the doorframe (no trim), you’ll probably
have to remove the siding or cut it back
and restore it after installing the door in
order to achieve a leak-free installation.
And if you have stucco or brick, you’ll
probably have to add trim to fill the gap
and rely partly on high-quality caulk to
seal out water. We’ll talk more about this
later.
You never know how smoothly a patio
door tearout and installation will go, so
start in the morning to give yourself the best chance to finish up before nightfall. If
you’re not going to beat the witching
hour, cover the opening from the inside
with sheets of plywood cut about 6 in.
larger than the opening. Run 3-in. screws
through the plywood and drywall into the
framing where the holes will be covered
by the interior trim. If it’s chilly out or
threatens to rain, also staple plastic over
the exterior to keep out drafts and water.
1. Pry the interior
trim free. Then
chip away drywall to
expose framing and
measure the rough
opening width (distance
between studs)
and height (floor to
beam). Then select a
new door that fits
that rough opening.
Removing the old door
Sliding patio doors are heavy (60 to 100
lbs. per panel), so it’s best to remove the
old panels one at a time and then tackle
the door frame. Start with prying free any
exterior trim pieces and then remove first
the sliding and then the stationary panel
(Photos 2 – 4). Usually the sliding panel
wheels rest on the bottom track and the
panel is held at the top by a removable
strip of wood called the “inside head
stop.” Unscrew the inside head stop and
remove the panel by tipping the top into
the room and then lifting the bottom
rollers free of the track (Photo 2). Some
doors may have a channel instead of a
head stop at the top, and you may need to
lower the door on its rollers using the
adjusting screws at the base to gain clearance
(Photo 11). Then lift the panel
straight up until the rollers are clear of the
track, and pull the bottom into the room
to free the panel.
Removing the stationary panel can be
trickier. Generally there’ll be an angle
bracket at the top and maybe one at the
bottom that you unscrew and remove
(Photo 3). Then slide the panel toward
the latch to clear it from the side jamb so
you can lift it free. If it won’t budge, use a
utility knife to cut through any paint or
caulk where it touches the frame and try
prying the top and bottom again. If it still
won’t come free, don’t beat yourself up.
Replace the angle brackets so it won’t fall
out later and go to the next step of cutting
the jambs free from the opening. Cut
through insulation, fasteners and shims
with a reciprocating saw sporting an 8-in.
bimetal blade (Photo 5). Most likely, the
threshold will be glued to the floor with
beads of sealant, and it may take substantial
prying with a flat bar to free it. Then
get a buddy to help lift out the frame
along with the panel. Cut up the frame in
chunks for disposal.
Click Image to enlarge.
2. Latch the door,
then unscrew and
remove the inside head
stop. Unlatch the door,
tip the top of the sliding
panel inward and
lift it free of the track.
3. Unscrew and
remove any angle
brackets at the top
and bottom of the
stationary panel.
Click Image to enlarge.
4. Pry the stationary
panel free of the
frame at the top and
bottom, slitting caulk
or paint as necessary
with a utility knife. Tip
it inward and lift it free.
Check the floor for level
In rare situations, the floor under the door
will be out of level. Sweep the floor free of
debris and check it with a straight board
and a 4-ft. level. If it’s within 1/4 in. of
level over the 6-ft. opening, let it be; the
door should still slide smoothly. But correct
larger variations with two long,
tapered shims placed directly under the
sill (use treated wood on concrete). Fill
any voids with polyurethane caulk to keep
out drafts.
Leakproof flashing
In general, the directions that come with
the door will be fine for assembly and
installation of the new unit. Unfortunately,
they assume you’re installing the
door in a new wall that doesn’t yet have
exterior siding. Replacing an old door can
be a bit more complex.
Begin flashing at the bottom. Apply
flexible flashing directly under the doorsill
and 2 in. up the sides (Photo 6). Flexible
flashing comes in 4- to 6-in.-wide rolls ($10) and has a sticky side so it adheres to
the underlying surfaces. It’s thick and seals
around fasteners that are driven through
it. It’s imperative that the flashing laps
well over any deck flashing or weather
barrier below the door (Photo 6). You
may have to overlap two rows, as we did,
to get the necessary coverage. Pros will
usually rest the new doorsill (caulked)
directly on the flashing, but for further
protection in wet locations (rain will
splash against the door bottom from all
angles), add a “sill pan” as well (Photo 7).
We chose a Jamsill Guard ($40; see Buyer’s
Guide, below). It comes in three separate
parts that glue together with PVC cement.
Next apply flashing over any building
paper, house wrap or sheathing along the
sides and fold it around the door frame
opening. We couldn’t work the sticky
flashing behind the vinyl trim, so we
tucked No. 15 roofing felt about 2 in.
under it instead.
Our slider was sheltered by a wide, low
soffit, so we didn’t have to worry about
top flashing. But if your slider is unprotected,
leave the top fin intact and slip it
under the weather barrier (felt, house
wrap, etc.) under the siding when you
slide the new door frame into the opening. Then slip in a drip cap (usually
included with the door) up under the
weather barrier as well (Figure A). Follow
this basic principle: Keep water flowing
toward the exterior surface, just like
shingles do.
5. Pry off the
exterior trim,
then cut between
the door frame and
the framing with a
reciprocating saw.
Pull the entire frame
from the opening.
Click Image to enlarge.
6. Lay flexible
flashing over the
sill, wrapping it up
the opening sides at
least 2 in. and over
any flashing or
siding below.
Click Image to enlarge.
7. Prep and lay a
special vinyl sill
pan over the flashing.
Clean the joint overlaps
with PVC cleaner,
then lay the parts in
place and weld the
seams with PVC
cement.
FIGURE A New door flashing details
Click Image to enlarge.
Buying a patio door
Sliders are built from a variety of
materials including aluminum, wood
and vinyl. Low-maintenance selections
include either vinyl or aluminum
exterior cladding over wood core,
solid vinyl and all-aluminum. If you
want a slider that matches existing
windows, consider buying the same
brand. Check markings on existing
window hardware to find out which
brand you have.
Looking at the door from the outside,
the operable panel determines
whether it’s a right- or left-handed
unit. Don’t be afraid to switch the way
your original door opened if changing
it makes access easier or furniture
arrangements better. But be aware
that heating vents work better in front
of the stationary panel. They don’t
stand up well to foot traffic.
Installing the new door
Installing your new slider is usually the
easiest part of the job. Be aware that every
manufacturer has slightly different
weatherstripping systems, handle and
lock hardware, and ways to fit the doors
into openings, so they may not exactly
match the ones shown in our photos.
Read and follow the door instructions for
those details.
If you have a “knockdown” (not preassembled)
door frame, assemble it on
the deck, garage floor or other flat surface.
“Dry-fit” the assembled door frame
in the opening to make sure everything
fits (Photo 8), then rest it flat and put
two beads of silicone caulk on the underside
of the sill (where the directions call
for it). Slip the door frame back into the
opening and push the door fins tight
against the sheathing (Figure A). (Line
the fin groove up flush with the outside
of the sheathing if you’re not using fins.)
Center the door frame in relation to the
siding or trim. Otherwise it’ll look bad
from the outside. Then plumb, shim and
screw the door in the opening (Photo 9)
following the manufacturer’s instructions.
Be sure not to bow the jambs in or
out when you drive the screws.
Follow the instructions to install the
stationary panel first and then the slider.
Tip the stationary panel into the opening
and slide it within about 1/4 in. of the
side jamb, and make sure the gap is even
top to bottom. If it’s more than 1/4 in.
out of plumb or the jamb bows, adjust
the frame for plumb and straightness
and adjust the shims if necessary. Install
angle clips, weatherstripping and trim as
needed.
Then rest the sliding panel wheels on
the tracks and tip the panel into the
opening. Have a helper hold it in place
while you screw in the head stop. Slide
the door about 1/4 in. from the frame
and check the gap from top to bottom.
Raise or lower the rollers at the bottom.
Adjust the rollers until the gap is even
and the door rolls freely (Photo 11). Finish up by installing the handle and the
locking hardware.
8. Assemble the
frame following
the manufacturer’s
instructions. Apply
two beads of silicone
caulk along the length
of the threshold and
tip the frame into
the opening.
Click Image to enlarge.
9. Center the frame
in the opening and
screw it into place,
using a level and
shims to square it.
Check the frame for
square and make final
adjustments when you
install the stationary
panel.
Click Image to enlarge.
10. Tip the stationary
panel into
the opening, push it
against the door frame
and install any angle
brackets to anchor it
(Photo 3). Tip the operable
panel into place
and screw the inside
head stop to the top
of the door frame.
Finishing up the inside
Standard slider doorjamb depths are
designed to fit standard 4-9/16-in.-thick
walls (2x4 studs plus 1/2-in. drywall and
sheathing). If your walls are thicker, as in
our case, you’ll have to add extension
jambs (Photo 12). Cut the top piece to
fit first, then shim it and nail it in place.
Then install the side extension jambs.
Leave an even 1/8-in. reveal (backset)
between the extension jamb and the
doorjamb.
Insulate around the frame with fiberglass
packed tightly against the exterior
sheathing and more loosely near the drywall.
(Foam insulation is a bit more difficult
to use because even minimal-expanding
types can bow in jambs and
affect weatherproofing or door operation.)
Add interior trim around the door,
leaving another 1/8-in. backset between
the trim and the extension jambs.
Finishing up the outside
You’ll frequently be installing a door
that’s smaller than the one you removed.
This will leave a wider gap that you’ll
have to fill with exterior trim. Match the
new trim to the existing as much as possible.
Whatever trim you choose, rip the
trim slightly narrow so you leave 1/8-in.
gaps on both sides. Seal these gaps with a
high-quality acrylic or silicone caulk.
Finish up your installation by screwing
or nailing a 3/4- to 1-in.-thick piece of
cedar, treated wood or composite material
directly under the overhanging lip of
the threshold to support it (Photo 13).
Some sliding door manufacturers offer a
premade aluminum support strip as an
alternative.
11. Slide the door
slightly open
and adjust the roller
heights until the gap
between the jamb
and the panel is
consistent.
Click Image to enlarge.
12. If you need
extension
jambs, rip them to
width and then shim
and nail them into
place, leaving a
1/8-in. reveal at the
door frame. Then
add the casing with
another 1/8-in. reveal.
13. Cut filler strips
to fit between
the door frame and
the siding with a
1/8-in. gap on both
sides, then fill the
gaps with silicone
caulk. Cut a threshold
support block to fit
between the deck and
the siding, then slip it
into place and nail it.
Buyer’s Guide
Jamsill Inc., www.jamsill.com,
(800) 526-7455. Have your patio door brand,
size and style selected before ordering. The
staff will help you select the correct unit.
Or try a full-service lumberyard to see if it
carries a similar product.
