DIY RV Window Install in a Promaster Camper Van

DIY RV Window Install in a Ram Promaster:

Our Ram Promaster 2500 was a cargo van, with the only windows in the cargo area located in the back doors. We knew that we wanted additional RV windows installed for light and ventilation. We first finalized our floor plan, which then allowed us to determine the best window locations. We decided that we wanted to install three windows: one on the driver side over the bench sofa seat, one in the sliding door, and a third on the passenger side over the galley.

Since the walls of the Ram Promaster van are nearly flat, it is possible to install a flat (not curved) framed RV window into this van. We were looking for windows that were operable and were about 3 feet long and 16 to 20 inches tall. Some of the window options that we considered were CR Laurence RV windows, Motion Windows for the Promaster, and Arctic Tern windows by Tern Overland. All three options had advantages. The Arctic Tern windows is a double pane acrylic plastic window that was the most insulated. However, it is prone to scratches, expensive, and is not tinted. The Motion Windows fit the slight curve of the van wall best, but were also more expensive than the CR Laurence slider windows. We actually like the awning style windows best, since they can be left open in the rain and prevent water from entering the van, but only the Tern window was an awning style. We ended up finding some new, old stock, RV windows from a surplus seller on Ebay. We were able to purchase three awning style, tinted RV windows with the interior trim ring for about half the price of the next less expensive option.

DIY RV Window Install
Awning style RV window from a surplus seller on Ebay.

Once we had our windows in hand, we needed to determine how thick the frame would need to be. The RV windows are installed by clamping the exterior lip of the window against the van body, then an interior frame then takes up the space between the van body and the interior trim ring. In our case, the thickness between the exterior and interior flanges was about 2.5 inches. We used a 1 inch thick polyisocyanurate foam frame against the van metal, and then a 1.25 inch thick wooden frame on the interior, plus a 1/4 inch spacer to make up the 2.5 inch thickness.

DIY RV Window Install
DIY RV window install – frame thickness detail

The wooden frames were built from pine and assembled using pocket hole screws and a Kreg jig. Once glued and assembled, the frames were primed with a quality primer to seal the wood against moisture.

DIY RV Window Install
The RV window wooden template before being painted with primer. Corner blocks were added to support the curved corners of the interior trim ring.

A cardboard template was made that was just slightly (1/8 inch or so) larger than the actual window hole needed to be. The inside wall stiffener had to be removed, but this can be easily done with tin snips and then a heat gun to release the foam adhesive. The cardboard template was aligned on the inside at the desired location, and then a small hole was drilled through the side at the top and center of the template. This allowed the template to be transferred to the exterior side. On the exterior, the template was aligned and squared to the body ridges and lines so that it would look straight from the exterior of the van.

DIY RV Window Install
Location of the RV window. The stiffener was removed, then a template placed at the desired location. The tiny hole in the green tape is the top and center of the cardboard template.

Now, on the outside of the Promaster van body, the outline of the template was drawn onto the paint. Painters tape was then applied exactly on the template line – this would be the line to cut with the metal saw. The tape would also prevent the metal saw base from scratching the painted finish. The moment of truth was at hand.

DIY RV Window Install
Painters tape applied along the exact line to cut that was traced around the template.

A drill but just large enough to allow the saw blade to be inserted was used to drill a starter hole. The jig saw with a new, quality metal cutting blade was slowly guided around the edge of the tape, which was our template line to be cut. Once part of the hole has been cut, a helper or some large pieces of tape are helpful to hole the metal piece in place so that it will not fall unexpectedly.

DIY RV Window Install
The first giant hole in our van for the RV awning window. Be sure to vacuum up any and all metal shavings from the interior.

Once the entire hole was cut, we filed the opening with a metal file to remove any sharp areas and we painted the bare metal edge with primer to prevent rust. The painters tape was then removed, and we cleaned the exterior around the hole with denatured alcohol to remove any dirt or residue. The exterior window flange was also cleaned before we applied one layer of butyl sealant tape to the window flange that would be against the Promaster van exterior surface.

DIY RV Window Install
The first RV window is placed in the opening after butyl tape is applied to the flange.

Now, going to the inside, we ran a bead of Sikaflex 221 sealant along the edge of the metal opening. The foam frame was then place against the metal body, followed by the wooden frame, and then our 1/4 inch spacers to take up the space until we installed the finished wall planking. The metal RV window trim ring was aligned, and we used #8 size by 3/4 inch screws to tighten the trim ring. We pre-drilled our screw holes, but self-drilling screws could also be used. This pulled the window tight against the exterior and squeezed out some of the butyl sealant – as was expected.

DIY RV Window Install
Interior view of the RV awning style window in our Ram Promaster van.

With one window finished, we moved to the passenger side. Two more RV awning type windows of the same size would be installed on that side. We chose to purchase three windows that were all identical. They are approximately 37 inches long by 17 inches tall. Having three RV windows of the same size did make the job somewhat easier, since our template and all interior frames were the same.

DIY RV Window Install
In progress on the passenger side. The window has been installed in the slider of our DIY RV Promaster, and the third window hole has been cut.
DIY RV Window Install
Interior view of the two passenger side RV awning windows.

The butyl tape sealant did continue to squeeze out over the next several days. This can be carefully trimmed with a plastic knife or scraper, and then the residue cleaned off the paint. We are very happy with the results of our window installation. The windows will provide nice views from the interior, and the slider window is very helpful when driving since the Promaster has a blind spot at the slider if a window is not installed. I have listed our tools and materials below that were used on this window project. I hope this information is helpful if you decided to perform a window installation.

DIY RV Window Install completed photo
Final look of the passenger side of the Promaster DIY RV. Note the butyl tape is the light colored material around the window trim. This can be easily removed later.

Tools and Supplies:

We also have produced a Youtube video detailing the RV window install that provides a bit more detail. Click the image below to view the video.

DIY RV Window Install youtube video screen
Youtube video detailing our DIY RV window install in the Promaster.

Happy Trails…