Sunday, December 3, 2023


The importance of an insert molding screw cover. Have you inspected yours?

By Dustin Simpson, California RV Specialists
In my experience, one of the most missed items on an RV is the insert molding screw cover. This protective plastic covers the screws at the roofline edges as well as the vertical and horizontal side seams of all RVs.

Unless you visually inspect under the insert moldings, you will not see the potential for water damage until it’s too late.

What’s the point of insert moldings?

Insert moldings help to keep the moisture, condensation, rain, dirt and other elements out of your RV. By sealing the edges of the aluminum molding it protects the screws along the roof, body, front and rear seams. This is important and, from my experience, is often a missed step when weatherproofing and protecting your unit.

When water gets past this plastic insert molding screw cover, it can cause serious damage. Water spreads through the unit and invites the growth of mold and rusting screws, in addition to causing dry rot in walls, roof joints and floors as the water travels down the aluminum framework in the wall.

Do I need to replace it?

I recommend that you replace the insert molding as needed every 2-3 years.

Insert molding screw covers shrink in both directions and will allow water to get in. This shrinking is caused by age, sun, soaps and elements. The telltale sign is tapping it and seeing if it makes noise within the track.

Replacing the insert molding screw cover

Make sure when replacing the insert screw cover that you go back and tighten the screw just a little bit. If they are stripped out or not holding, you can replace them from a size #8 to #10. You can also add additional screws as needed in between the screws every 3 inches. All aluminum moldings are pre-drilled every 6 inches.

In many cases, we find that the moldings were cut during installation and the pre-drilled holes are missing, which means some screws were never added when the unit was built. This simple miss causes it to separate and allows water to damage your unit. I tend to overdo it and will typically install a second screw at the ends that I refer to as “toenails.” This helps keep the molding in place.

Additionally, I never tuck the insert molding cover behind at the ends. This traps the water and doesn’t allow it to drain. If this occurs, the molding collects dirt and mold within the screw cover.

When removing and replacing your insert molding, be sure to brush any dirt out of the tracks. When installing, I use a plastic scraper to tuck the edge in while feeding the trim into the molding. This will make it nice and easy to install. I like to add screws at the ends to secure the molding in place or use the corner caps.

What size insert molding do I need?

Insert moldings come in two sizes: 3/4” and 1”. In most cases, the 1” is used at roof lines, side wall edges and corner moldings. The 3/4” is sometimes used at entry doors and around compartment doors.

Don’t forget to check for insert moldings at slideouts’ side edges, drip rails and topper mounting rails.

I really hope this information is helpful to you to prevent damage. It will protect your investment.



RV Travel
RV Travel
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wanderer (@guest_184383)
1 year ago

Thanks for this very helpful article!

Brad (@guest_184324)
1 year ago

After an unfortunate encounter with a tree limb that stripped away a big section of the vinyl insert along the roof line of our trailer I found that the screws holding the molding in place had become rusted. Before replacing the old screws with larger stainless steel ones I injected the screw holes with a marine-grade wood hardener to arrest any rot that had formed and added a dab of lap sealant to the screw to seal the hole, then inserted new molding.

Ron (@guest_184298)
1 year ago

Could not agree more. I actually had a screw missing, which led to a major leak. I replced screw, caulking all the heads, inserted new molding and caulked top and bottom of molding. There are plenty of YouTube videos that show how to insert molding.

Bob M (@guest_184293)
1 year ago

Insert molding is just another cheap way the rv industry gives us junk. There’s got to be better ways to do it. The molding is cheap garbage that cracks and deteriorates from the sun. Easy way to do is on a sunny day let the molding in the sun. While you remove the old molding. This makes it easier to slightly bend the molding to fit in the Alum track.

Dustin Simpson (@guest_184307)
1 year ago
Reply to  Bob M


Thank you so much for replying. Here is a video that we did awhile back that sure to hit right on your point.

We see this all the time no matter the brand or manufacturer. You can almost find this on every unit. Sometimes it’s only a few screws and sometimes it’s every other screw.

check out this video and let me know what you think.

Thank you

mimi (@guest_184281)
1 year ago

A video demonstration would be most helpful.

Larry (@guest_184289)
1 year ago
Reply to  mimi

And more photos. I’m not even sure this exists on my motorhome.

G13 (@guest_184297)
1 year ago
Reply to  Larry

Photo does not do justice to your topic.

Dustin Simpson (@guest_184306)
1 year ago
Reply to  G13


Here is the same link above as well as an additional link of a 2018 Grand Design RV that is full of dirt and damage.

Dustin Simpson (@guest_184305)
1 year ago
Reply to  Larry


Here is a link to my main business Facebook page that has 80 pictures in this folder to show you lots of examples of damage.

Dustin Simpson (@guest_184304)
1 year ago
Reply to  mimi


Here is a video that we did awhile back that will show you more about insert moldings and show you some damages.

Jeanne (@guest_184422)
1 year ago
Reply to  Dustin Simpson

Thanks Dustin,
your videos were very helpful. The original article would have made more sense with more pictures.

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