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Camper Vans Part 6: Adding Windows

Posted by Greg Keith on

Sprinter van before adding rear windows

Want to build a camper van? In this series of Campervan HQ blog posts, we'll discuss doing just that. For a more detailed discussion, see my 378-page Sprinter RV Conversion Sourcebook.

Now that you've started your build by getting the interior of the van ready for your camper van conversion, it's an excellent time to add opening for windows, skylights and vents. Terrifying though it is to cut into the metal of your expensive new van with a saw, it's necessary, and it's really not that hard to add windows if you take some care while planning and performing the cuts.



1) If you're installing bonded (glue-in) windows, do not attempt to install your new van windows in an unheated space where nighttime temperatures will fall near or below 40°F. Either install the windows in a heated space or wait until temperatures are warm enough to be suitable for the adhesive to cure properly. The van, glass and adhesive must ideally all be at the same temperature.

2) Any metal shavings must be collected and removed from contact with the van's sheet metal exterior or interior immediately. Any metal shavings will start rusting rapidly (within 24 hours given any moisture present), which may permanently damage your van's paintwork.

Adding Van Windows

There are several tools you might use to cut the openings (before using any of these tools, make sure you're wearing gloves, eye protection and hearing protection - they all produce a surprising amount of tiny metal shavings and lots of noise):

  • Jigsaw - A jigsaw with a many-toothed metal blade (rather than a coarser-toothed wood blade) is a good tool to use for cutting the openings. However, because of the oscillating motion of the blade, it tends to hammer against the metal (set to to "smooth" if your jigsaw has that option), so you need to take special care to use plenty of tape all around your cut lines, both on the exterior (to prevent paint scratching) and on the interior (to prevent lots of small, sharp metal flakes from being scattered everywhere).
  • Air Nibblers - Air nibblers are another excellent tool for cutting window openings. They can typically easily cut up to 14-gauge steel, produce a lot less metal trimmings, and vibrate less than a jigsaw. However, they can be a little cumbersome to handle, depending on what you're cutting.
  • Center-Blade Shear - Makita, DeWalt and Milwaukee all make center-blade shears which work well for cutting openings for windows and vents on your camper van. This will produce less vibration than a jigsaw, produces a very accurate cut if used carefully, though just as many trimmings.

How to add van windows

1. To start the cuts for your openings, if the exact shape is not clear, you may need to first drill pilot holes or tap outlines with a punch. When you've cut the openings, make sure that you dab the edges of the cut metal with rustproofing paint. You can use a small sponge-like dab tool rather than a brush.

Masking Sprinter van rear door before cutting

2. Depending on the type of window you're installing, you may have both an exterior seal created with urethane adhesive) and an inner trim ring:

    • For bonded windows - If the window is a new install in a new opening, you will need to prime both the glass where the glue bead will be attached, and the body sheet metal where the adhesive will go (for example, with CRL Powr-Bond Primer. Note that primer vapors are explosive and dangerous, use primer in a well-ventilated area). Shake primer for one minute before use, apply with clean dauber/brush, then let dry for 10 minutes.
    • For both bonded and clamp-in windows - If the window is a new install in an existing opening where a window was mounted before, ensure you clean off all of the previous urethane adhesive used with a blade, working carefully to ensure you don't cut too deeply and scratch the van's body paint. Ensuring you remove as much of the old urethane as possible will help ensure you get a good seal with the new window.
Old urethane outline on Sprinter window opening
  • If you have a clamp-in window, unscrew the inner trim ring from the window, using either hand tools or very carefully with power tools, making sure not to strip the trim ring screws.

3. Fit the window in place in the opening to check for correct fit. If all looks right, pop the window out of the opening again.

4. For bonded windows - prime the area where the adhesive will go, then lay a thick bead of urethane adhesive all the way around the window opening (CRL Powr-Bond Urethane Adhesive is a good choice for window glue).

Almost finished cutting window opening in Sprinter van rear door

5. Carefully position the van window in the opening, then press it into place against the adhesive. Make sure all window edges are at a uniform height from the sheet metal of the van body.

Freshly cut window opening for Mercedes Sprinter van rear door window

6. For clamp-in windows - Once the van window is in the exact position where you want it, mount the inner trim ring back onto the inside of the window and secure it in place with the trim ring screws. On many windows, the screws on the inner trim ring are easy to strip - either hand-tighten these screws, or use power tools for tightening them very carefully.  Do not tighten each screw all the way the first time - rather, tighten each screw partially, moving clockwise, and when you have tightened all the screws initially, do a second round of tightening. Again, check the position of the window edges, you can still adjust the positioning a little if necessary.

7. If the window positioning is now correct:

For bonded windows - let the adhesive cure and don't move the van until 4-48 hours have passed. The curing time will differ hugely depending on the temperature and humidity where you are performing the install (a rough baseline: 3 hours full cure at 73°F (23°C) and 45% RH (relative humidity).

For clamp-in windows - your install is done. Check for leaks as described in the next step. 

Finished rear Sprinter van windows

8. When the window glue has cured (for bonded windows) or 24 hours have passed and the exterior compression ring has flattened (for clamp-in windows), gently hose the closed window from outside with water. Check the inside carefully for any leaks. If you do have leaks, then on a clamp-style window you can:

    • Check the exterior compression ring flange around the outside of the window - sometimes a portion of the exterior compression ring flange can become compressed or distorted and thus not seal the exterior properly. If this happens, you can loosen the trim ring screws, correct the position of the exterior compression ring flange, then tighten the inner trim ring screws again.
    • Tighten the trim ring screws further. Clamp-style windows may need two rounds of tightening to get the external compression ring fully sealed against the van exterior. Just make sure you don't strip the trim ring screws while you're re-tightening!





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