Introduction #
Sun's Up doesn't normally install exterior doors. That's framing crew work. The one time we get pulled in is on a special request. A customer or GC (the general contractor running the job) asks us to come out at framing stage and set the exterior door ourselves, because the framing crew is doing a poor job of it. Most of the time that request is a house-to-garage door. That is a straightforward install with no weather on the other side of it. See How to Install a House-to-Garage Door for that full process.
This guide covers the harder version of that same special request. It covers a door that faces the weather: a front entry, a back patio door, or anything else with siding and the outdoors on the other side. It builds directly on the house-to-garage install. First, do everything in How to Install a House-to-Garage Door: set the unit, shim (wedge it into place with thin shims) and plumb (make it perfectly vertical) the hinge side, shim and adjust the latch side, then foam the gap between the jamb and the rough opening (the framed hole in the wall the door sits in). Hang and adjust the door. Then come back here and add the water-management steps below.
The extra work here is keeping water out of the wall, sometimes called building-envelope water management. You build a sill pan (a shallow watertight tray) under the threshold, then run flashing tape (a sticky, waterproof tape) up the jambs and across the head, tied into the house wrap where it's present. Each layer has to lap, or overlap, the one below it, the same way shingles overlap on a roof. Get that lap direction wrong and you build a path for water to get into the wall instead of a path for it to get out. Foam still does the air-sealing job it does on every exterior door. The pan and flashing are a separate water barrier, layered in before and around it.
Before You Begin #
Prerequisites #
- You're doing, or about to do, the full install described in How to Install a House-to-Garage Door: the unit set, the hinge and latch sides shimmed and plumbed, the jambs nailed off, and the gap foamed
- Sill pan flashing and self-adhering flashing tape are on site and staged before you set the door unit. The pan goes in first, ahead of the unit, not after
- The rough opening sill, jack studs, and header are clean, dry, and free of rot before you flash over them. Flashing over a damaged sill just hides the problem
- House wrap (WRB) is installed and accessible at the opening, so the head flashing can be tied into it. If it isn't up yet, flag it for the GC so the lap gets finished later. Don't skip it
- The subfloor at the threshold is level and structurally sound. A sagging or uneven sill throws off the pan's slope before you even start
What You Need To Know #
- This scope only comes up on special request. It's not a job we run into on our own. Confirm with the GC or customer that the door is really weather-exposed before you build a full water-management assembly a garage door wouldn't need
- Water management here is entirely mechanical: the sill pan, the shingle-lapped flashing tape, and the door's own threshold and weatherstripping. We do NOT run a caulk bead to the siding or under the threshold on this install. The pan and flashing do that job instead
- Every lap sheds water DOWN and OUT: the WRB laps over the head flashing, the head flashing laps over the jamb flashing, and the jamb flashing laps over the sill pan. Reverse any one of those, and you funnel water into the wall instead of out of it
- The sill pan goes in BEFORE you set the door unit. It is not something you tuck in afterward. Sequence matters here
- Foam from the core install is still the air seal between the jamb and the rough opening. The pan and flashing are a separate water barrier. Foam does not manage bulk water, so don't rely on it to
Tools Required #
Power Tools #
- Heat gun (optional; warms flashing tape for a solid bond in cold weather, not needed most of the year)
Hand Tools #
- J-roller (bonds flashing tape and membrane firmly to the sheathing)
- Utility knife
- Tape measure
- Putty knife or plastic scraper (sets pan flashing into corners without puncturing it)
Supplies #
- Sill pan flashing: a pre-formed rigid pan, or one you fabricate from self-adhering flashing membrane, sized to build a back dam (a raised lip at the back of the pan that keeps water from draining toward the house instead of away from it)
- Self-adhering flashing tape, compatible with the house's WRB
- Flashing tape primer (for cold weather or dusty/dirty sheathing only, to help the tape bond; this is a bonding primer for the membrane, not a sealant, and it does not replace or substitute for caulk anywhere on this install)
Materials #
- No additional materials beyond the door unit itself: a weather-rated pre-hung exterior door with its own integral threshold and weatherstripping, the same as covered in the core guide
Weather-Exposed Exterior Door: The Extra Steps #
Step 1: Install the Sill Pan (Before You Set the Unit) #
Before you set the door unit, build the sill pan in the rough opening. Use a pre-formed rigid sill pan sized to the opening, or fabricate one from self-adhering flashing membrane. Fold it up the jack studs at least 3 inches on each side, and up the back of the opening, to form the back dam. The back dam is what stops water that gets past the threshold from running back into the house instead of out of it.
Slope the pan toward the exterior, or use a pan with a built-in slope, so water drains OUT and never pools or runs back toward the house. Press the pan tight into the corners and against the subfloor and jack studs. No wrinkles, no voids, nothing that gives water a place to sit.
Pro Tip: The sill pan is the single most important part of this whole install. If you only get one thing right, get the back dam right. A pan with a weak or missing back dam will pass water straight into the house the first time wind drives rain against the door.
Step 2: Flash the Jambs #
Run self-adhering flashing tape up each jamb of the rough opening, starting at the pan and lapping DOWN onto it. The jamb flashing sits on top of the pan flashing, never tucked under it, so water sheds off the jamb and onto the pan instead of behind it. Extend the jamb flashing a few inches past the top of the rough opening, so the head flashing has something to lap over in the next step.
Roll every run of tape with the J-roller so it bonds fully to the sheathing. A bubbled or unbonded lap is a leak waiting to happen. It just hasn't happened yet.
Step 3: Set the Unit Into the Pan and Finish the Core Install #
With the pan and jamb flashing in place, set the door unit exactly as described in How to Install a House-to-Garage Door. Seat the threshold down into the sill pan, and center the unit in the opening. Then shim and plumb the hinge side, and shim and adjust the latch side.
The pan is what seals the threshold to the subfloor on this install. There is no caulk bead under the threshold. The threshold sits inside the pan's back dam, and that mechanical boundary is the water barrier, not sealant from a gun.
Once the unit is set and shimmed, foam the gap between the jamb and the rough opening the same way you would on a house-to-garage door. The foam is still the air seal. It isn't doing the water-management job the pan and flashing are already doing, so don't skip the flashing steps just because the foam is going in.
Step 4: Flash the Head and Tie Into the WRB #
Run flashing tape across the head of the opening, lapping it OVER the top of both jamb flashing legs (the flashing running up the two vertical sides of the opening). This is shingle-style, the same rule as everywhere else on this install: water always moves down and out, never up and in.
Where the house wrap is already installed, pull its head flap down over the head flashing and tape it off. That gives you a full shingle-lapped stack: the WRB sheds onto the head flashing, the head flashing sheds onto the jamb flashing, and the jamb flashing sheds onto the sill pan. Every layer above laps over the layer below it. If you find a spot where that's reversed, fix it before you move on.
If the WRB isn't up yet at framing stage, leave the head flashing's outer edge free, so the siding crew can lap their house wrap over it later. Tell the GC directly, so it doesn't get missed once the wall is covered up.
Step 5: Confirm Drainage and Test for Water Intrusion #
Before you close anything up, confirm the pan actually drains outward. Pour a small amount of water at the back of the pan, behind where the threshold sits, and confirm it runs out the front, not toward the house.
If you have hose access, run water over the head and jambs for a few minutes, and check the interior sill and jambs for any sign of intrusion. Trace the lap sequence with your finger from the head down to the pan. If you find one spot where an upper piece tucks under a lower piece instead of over it, fix it now. That's the spot that leaks in six months, not today.
Quality Check #
- Sill pan intact, no punctures, tears, or unsealed seams
- Sill pan slopes, or is built to drain, toward the exterior; no flat spots or reverse pitch
- Every flashing lap sheds down and out: head over jambs, jambs over pan, WRB over head flashing
- Threshold seats down into the pan's back dam with no caulk bead underneath
- No exterior caulk bead anywhere on this install; the pan and flashing are the water barrier, done mechanically
- Water test or a light rain shows no intrusion at the sill or jambs
Weather-Exposed Exterior Door Troubleshooting #
Water at the Sill After Installation #
Almost always a reverse lap or a gap in the back dam. Pull the interior sill trim and check the pan for a torn back dam, a gap at the corners, or a seam that never bonded. Re-lap and re-roll the tape. Extend the back dam higher if water is topping it. Then retest before you close the wall back up.
Flashing Laps the Wrong Way #
If you find the jamb flashing tucked under the pan, or the head flashing tucked under the jamb legs, that assembly is built to funnel water into the wall instead of out of it. Cut it loose, clean the surface, and redo the lap in the correct order: pan first, jambs over the pan, head over the jambs, WRB over the head. Don't caulk over a reversed lap to try to fix it. Re-lap it correctly instead.
Flashing Tape Won't Stick or Lifts at the Seams #
Cold temperatures and dusty or damp sheathing are the two most common causes. Wipe the surface clean and dry before applying tape. In cold weather, warm the tape with a heat gun before you roll it, or use a cold-weather-rated flashing membrane instead. Roll every seam with the J-roller. Hand pressure alone doesn't fully bond it, and a lifted seam is an open door for water.
