A camper door gets replaced for a small number of reasons, and none of them are subtle. The skin delaminates and bubbles. Water tracks in past a seal that no longer touches anything. The frame racks far enough that the latch stops finding the keeper. At some point a repair stops being worth the labor and you are buying a door.
The part that goes wrong is almost never the fitting. It is the ordering. A door built to the wrong opening is a door you cannot install and cannot return to the wall it was measured from. This article is the ordering path only: what to measure on the trailer you already own, what to tell the manufacturer, and what to check the day the crate opens.
Two companion articles carry the arguments this one skips. For whether to buy a custom door or an original-equipment one, read our guide to custom versus OEM RV doors. For the door types themselves and how sizing works across them, read the RV door buying guide.
Measure the opening, not the old door
The old door is the thing that failed. Measuring it copies the failure into the new one.
Delaminated skins swell, and a swollen door reads wider than the hole it sits in. A door that has sagged on worn hinges reads short on one side. Trim and flange overlap the opening by design, so the outside of a door is never the size of the hole underneath it. Take every number off the wall, with the trim removed, and take it in the order below.
The six numbers a door order is built from
- Opening width. Measure across the bare opening at the top, at the middle and at the bottom. Write down all three, not an average. If they disagree, the disagreement is the useful information.
- Opening height. Same method: left edge, center, right edge.
- First diagonal. Corner to corner, top left to bottom right.
- Second diagonal. Top right to bottom left.
- Wall thickness. Measure through the cut edge of the opening, skin to skin. This is what the door’s clamping depth has to match, and it is the number most often left off a quote request.
- Corner radius. Camper openings are usually radiused rather than square. Lay paper over a corner, trace it, and send the tracing. A traced corner is better evidence than a guessed number.
Record each one to the smallest division your tape reads, and write it down at the time rather than afterward. Photograph the opening with the tape in the shot, corners included. A photograph settles a question later that a number on its own cannot.
Before you request a quote
What a camper door order needs from you
All of it comes off the trailer you already own. None of it comes off the old door.
6
measurements to record off the bare opening
3
places to measure the width: top, middle, bottom
1
hinge side, always called standing outside the camper
3
glass options to choose from: tinted, frosted, clear
Counts summarize the checklist in this article. Glass options as listed on the SDG Doors & Windows doors page, read September 28, 2026.
Square is what the two diagonals are for
The two diagonals are the only measurement that tells you something the width and height cannot. If they match, the opening is square and a rectangular door will sit in it. If they do not, the opening is a parallelogram, and a correctly built door will bind on one corner and stand proud on the other.
That matters before you order, not after. An opening that is out of square has usually moved, and something moved it: a soft floor under the sill, a frame member that has let go, or a wall that has taken a hit. Fitting a new door into it transfers the problem straight to the new door, and the first symptom is the same latch trouble you had before. If the diagonals disagree, say so on the quote request and send the numbers. It changes what should be built and sometimes whether a door is the right purchase at all.
Hinge side, swing and where the latch lands
Hinge side is the field most often reversed on an order, because two people can describe the same door in opposite ways. Fix it with one convention and state the convention out loud: stand outside the camper, on the ground, facing the door. If the hinges are on your left, it is a left-hinge door. Write that sentence into the quote request rather than the word “left” on its own.
Note the same way whether the door swings out or in, and roughly where the latch sits in the height of the door. If your existing hardware is sound and you plan to keep it, say which parts you are keeping. SDG lists locks, handles, hinges and latches among the RV and trailer door hardware it stocks, so a door and its hardware can be sorted at the same time. Our guide to trailer door latches and locks covers choosing that hardware on its own.
What to specify besides the size
Size gets the door into the hole. The rest of the order decides whether you like living with it.
- Glass, or none. Tinted, frosted and clear panels are all offered. Tinted buys privacy and cuts light; frosted buys privacy and keeps light; clear buys the view.
- Insulation. Insulated construction is an option, and it is worth naming if the camper gets used in heat or cold rather than stored through it.
- A screen door. Screen doors are part of the door range, and specifying one with the entry door is simpler than adding one to a door already built.
- Shape. Custom dimensions and shapes to fit any size opening are the point of ordering from a manufacturer instead of hunting a part number. A radiused, out-of-standard or oversized opening is a normal order, not a special case.
All of it is built to the numbers you supply. SDG makes its custom RV and trailer doors in-house in Waycross, Georgia, and ships nationwide, so the opening you measured in a driveway anywhere in the country is the opening the door is cut to. The glass and screens are custom-cut the same way.
When the frame is the problem and the door is not
Before you order, press along the threshold and the lower few inches of the wall on both sides of the opening. Soft floor at the sill, a threshold that flexes underfoot, or a frame edge that crumbles when you pull the trim is a structural repair, and it is the reason the door failed rather than a consequence of it.
A new door hung in a soft sill sags on the same schedule the old one did. Repair the floor and the framing first, then measure, then order. The order in that sentence is the whole point: an opening repaired after measurement is a different opening from the one you measured.
Water is usually what did it, and water usually got in past a seal. Seals, cranks and trims are stocked alongside the door hardware, so a seal replaced early is a cheap way to avoid buying a door twice.
What arrives, and what to check before you cut anything
When the door arrives, check it against your own written numbers before the old one comes off the camper. Width, height, wall thickness, corner radius, hinge side, glass and screen. Do that on a bench or on the ground, with the notes and photographs you took at the start in front of you.
The reason for the order is simple. Once the old door is out, the opening is exposed to weather and the camper is not secure, and that is the worst position from which to discover a mismatch. Ten minutes of checking against your own notes costs nothing while the trailer is still closed up.
Frequently asked questions
How do I measure for a replacement camper door?
Remove the interior and exterior trim so the bare opening is visible, then record the width at three heights, the height at three widths, both diagonals, the wall thickness through the cut edge, and a traced corner radius. State the hinge side as seen from outside the camper. Photograph the opening with the tape in the frame.
Is there a standard size for a camper door?
Not one you should rely on for an order. Openings vary by builder, by model year and by whatever repairs a camper has had. That is why SDG builds to custom dimensions and shapes rather than to a catalog size, and why the measurements above are the order.
Can I replace the door without replacing the frame?
It depends on what is left of the frame, which is what the diagonals and the threshold check are for. If the opening is square and the sill is solid, the frame is doing its job. If it is not, the frame comes first. Send your numbers with the quote request and ask which route fits your camper.
What does a replacement camper door cost, and how long does it take?
SDG does not publish prices or lead times, so any figure quoted here would be invented. Both are answered against your measurements on a quote request.
What about the threshold?
Check it before you order, not after. A threshold that flexes, holds water or shows soft floor beneath it is a repair in its own right, and it changes the measurements you are about to take.
Send the numbers and get a quote
If you have the six measurements, the hinge side and a photograph of the opening, you have everything a quote needs. Contact SDG Doors & Windows with them, and we will build the door to the opening you measured and ship it to you.